Linseed oil or tuna oil supplementation in slow-growing chicken diets: Can their meat reach the threshold of a “high in n-3 polyunsaturated fatty acids” product?

Linseed oil or tuna oil supplementation in slow-growing chicken diets: Can their meat reach the... SUMMARY A strategy for enriching the meat of slow-growing chickens with n-3 fatty acids from tuna oil (TO) or linseed oil (LO) is proposed. The effects of TO or LO supplementation on the growth performance of the chickens and the quality, cholesterol content, and fatty acid composition of the meat were examined. A total of 560 21-day-old mixed-sex Thai indigenous crossbred chickens was assigned to a completely randomized design with 7 treatment diets and 4 replicates. The control group consumed a basal diet of corn-soybean meal supplemented with rice bran oil (RBO; 6%). In the experimental diets, RBO was replaced with 2, 4, or 6% TO (TO2, TO4, and TO6) or with 2, 4, or 6% LO (LO2, LO4, and LO6). All groups received 6% added oil. The TO6 diet lowered the final BW and FCR. The boiling loss of breast meat was highest in LO6 and differed from the losses in the control and TO2 groups. Meat from TO4 and LO6 yielded the lowest n-6/n-3 ratio. The alpha-linolenic acid (ALA) content linearly increased across the LO group. The n-3 fatty acid accumulation in the slow-growing chickens was nutritionally valuable for human consumption. Breast meat from TO2 and TO4 provided >250 mg docosahexaenoic acid (DHA) per 100 g fresh meat. Thigh meat from at least 2% TO or 6% LO contained >80 mg (eicosapentaenoic acid + DHA)/100 g meat and 600 mg ALA/100 g meat, respectively, reaching the “high in n-3 polyunsaturated fatty acids” threshold in dietary recommendations. DESCRIPTION OF PROBLEM The beneficial effects of n-3 polyunsaturated fatty acids (PUFA)—maintaining heart health, protecting against cancer and birth defects, and offsetting the symptoms of diabetes—have been known for many decades. Low levels of eicosapentaenoic acid (C20:5n-3; EPA) and very low levels of docosahexaenoic acid (C22:6n-3; DHA), which have been recently observed in the blood of people throughout most of the world, are associated with increased risk of cardiovascular-related mortality [1]. Therefore, increasing n-3 PUFA consumption by supplements or functional food is recommended. De Smet and Vossen [2] reported that poultry more easily responds to dietary n-3 PUFA supplementation than pork, lamb, or beef. Moreover, the conversion of alpha-linolenic acid (C18:3n-3; ALA) to long-chain n-3 PUFA is better in slow- and medium-growing birds than in fast-growing birds fed the same diet [3]. In certain regions of the world, consumers prefer the tasty, chewy meat from native chickens to the meat from commercially bred broilers [4]. The emergent market of functional foods has inspired the production of slow-growing chicken meat with a lower fat content and a healthier fatty acid (FA) profile for this niche market. In tropical Asia, non-food grade tuna oil (TO) and rice bran oil (RBO) are readily available in large amounts [5]. Such affordable oil supplements in slow-growing chicken diets might enable small and medium entrepreneurs to produce value-added meat. However, tuna has markedly declined in the global marine vertebrate population [6]. A possibly better alternative is linseed oil (LO), which is rich in ALA. In fact, chickens fed on diets supplemented with LO or fish oil yielded similar proportions of total n-3 PUFA in their breast meat, and the LO-fed chickens yielded higher n-3 PUFA content, especially ALA, in their thigh meat [7]. However, in male Cobb chickens subjected to transient high-temperature stress, fish oil (8.0%) caused higher mortality than palm oil or no added fat [8]. Hence, the level of fish oil in chickens’ diets should be reduced in tropical conditions. The fat content is lower in slow-growing chickens than in commercial broilers [9, 10]. Like turkey meat [11], slow-growing chicken meat rarely achieves the “source of n-3 PUFA” threshold in dietary recommendations. To address this problem, the present study investigated an enrichment strategy for slow-growing chicken meat, in which part of the dietary RBO is replaced with TO or LO. After applying this strategy, the n-3 PUFA content in the meat of slow-growing chickens is expected to meet the health recommendations of the European Union, while the growth performance and other quality characteristics are only marginally affected. MATERIALS AND METHODS Birds and Housing All procedures in the present study were approved by the Ethics Committee on Animal Use of the Suranaree University of Technology, Thailand. The chickens were Thai indigenous crossbreeds called “Korat meat chickens.” The chicks were vaccinated against Marek's disease at the hatchery, against Newcastle disease and infectious bronchitis on d 7 and 21, and against Gumboro disease on d 14. After hatching, the chickens were kept together until 21 d of age (an average BW of 271.68 ± 38.07 g), then transferred to the experimental pens. From d 1 to 21, the chicks were fed a corn-soybean meal-based diet (21% CP and 3,100 kcal ME/kg). The total FA content of this diet comprised 41.07% n-6 PUFA, 3.51% n-3 PUFA, 32.80% monounsaturated fatty acid (MUFA), and 22.63% saturated fatty acid (SFA). In all treatments, the birds were reared on floor pens (8 birds/m2) under similar environmental and management conditions until 84 d of age. The floor pens were layered with rice hulls (depth 5 cm) as bedding. Feed and water were freely available to all chickens. Experimental Design and Diets The experimental model was a completely randomized design, which included 7 treatment diets, 4 replicates, and 20 21-day-old mixed-sex chicks per replicate. The control diet was a basal formulation of corn-soybean meal containing 6% RBO. In the treatment diets, part of the RBO content was substituted with 2, 4, or 6% TO or LO. Note that the total oil content of all diets was 6%. All experimental diets were formulated with equal nitrogen levels and provided 3,100 kcal ME/kg. The CP was 19% for the grower diet (d 22 to 42) and 17% for the finisher diet (d 43 to 84) (see Table 1). Feed-grade oils were used in all experimental diets. RBO [12] is rich in C18:1n-9 (42.31%) and C18:2n-6 (LA; 32.77%) but its ALA levels are very low (1.45%). DHA is predominant in TO [13] (30.38%), while ALA constitutes 57.83% of LO [14]. Table 1. Compositions and calculated nutrient contents of grower and finisher diets (g/100 g diet, as-fed basis). Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 1Type and level of oil depends on the treatment. The diet was supplemented with rice bran oil and either tuna oil or linseed oil at 0, 2, 4, or 6%. The total amount of added oil in all treatments (including the control) was 6%. 2Premix (0.5%) provided the following nutrients per kilogram of diet: 15,000 IU vitamin A; 3,000 IU vitamin D3; 25 IU vitamin E; 5 mg vitamin K3; 2 mg vitamin B1; 7 mg vitamin B2; 4 mg vitamin B6; 25 μg vitamin B12; 11.04 mg pantothenic acid; 35 mg nicotinic acid; 1 mg folic acid; 15 μg biotin; 250 mg choline chloride; 1.6 mg Cu; 60 mg Mn; 45 mg Zn; 80 mg Fe; 0.4 mg I; 0.15 mg Se. View Large Table 1. Compositions and calculated nutrient contents of grower and finisher diets (g/100 g diet, as-fed basis). Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 1Type and level of oil depends on the treatment. The diet was supplemented with rice bran oil and either tuna oil or linseed oil at 0, 2, 4, or 6%. The total amount of added oil in all treatments (including the control) was 6%. 2Premix (0.5%) provided the following nutrients per kilogram of diet: 15,000 IU vitamin A; 3,000 IU vitamin D3; 25 IU vitamin E; 5 mg vitamin K3; 2 mg vitamin B1; 7 mg vitamin B2; 4 mg vitamin B6; 25 μg vitamin B12; 11.04 mg pantothenic acid; 35 mg nicotinic acid; 1 mg folic acid; 15 μg biotin; 250 mg choline chloride; 1.6 mg Cu; 60 mg Mn; 45 mg Zn; 80 mg Fe; 0.4 mg I; 0.15 mg Se. View Large Sampling and Measurements Growth performance. The weight gain and FCR values were calculated from the BW and feed intake, which were monitored once a wk in each pen. The occurrence of mortality also was recorded. Sampling. At 84 d of age, chickens weighing within 10% of the mean of the experimental unit were processed after a 12-hour feed withdrawal period. After the selection, 112 birds were transported to the university slaughterhouse, where they were stunned by electricity, scalded, and de-feathered by machine, then manually eviscerated. The functional properties (pH, drip loss, cooking loss, and shear force) were measured in meat samples from 2 chickens (one male and one female) per experimental unit. Breast and thigh meats were sampled from 2 other chickens (one male and one female per pen), then stored at –20°C until required for FA profiling and cholesterol content analysis. pH Measurement. The pH of the breast fillet was measured directly by a pH meter with a precision of 0.01 pH units [15] coupled to a probe inserted into the center of the pectoralis major muscle. The probe depth was 0.5 to 1.0 cm. Water-Holding Capacity. After chilling for 24 h, the water-holding capacity was determined as the drip loss (when samples were placed in an airtight container and hung in a chilled room for 24 h at 4°C) and cooking loss (when samples were boiled in a water bath in open plastic bags until the internal temperature reached 80°C). Shear Force Measurement. The peak shear forces of 3 subsamples (2.0 cm × 1.0 cm × 0.5 cm) were measured by a texture analyzer [16] equipped with a Warner–Bratzler shear force apparatus. The crosshead speed was set at 20 cm/min [17]. Fatty Acid Analysis. The lipids were extracted from approximately 5 g of each muscle sample [18], and 20 to 25 mg of the extracted fat were then methylated [19]. The fatty acid methyl esters (FAME) were analyzed using gas chromatography [20] with a capillary column [21] and a flame ionization detector. The carrier gas was helium at a flow rate of 0.95 ml/min. The injector and detector temperature was 260°C. The column temperature was raised from its initial 70°C to 175°C at 13°C/min, and finally raised to 240°C at 4°C/min [22]. Meat Cholesterol. The cholesterol content was measured in the raw breast and thigh meat [23]. The cholesterol was analyzed using gas chromatography [24] with a capillary column [25] and a flame ionization detector. The temperatures of the injector and detector were 260 and 300°C, respectively. Separation was carried out isocratically at 300°C with helium gas flowing at 1 mL/min [26]. Statistical Analysis and Calculations Analysis of variance was performed by a GLM procedure for completely randomized design. The procedure was implemented in SAS University Edition [27] using the pen mean as the experimental unit. Significant differences among the treatment means were determined by F-test and assessed by Tukey's multiple comparison tests. Differences between oil sources and control or between different types of added oils were tested using orthogonal contrasts, whereas the effects of different levels of TO or LO were tested by polynomial contrasts. Overall differences among the treatment means were considered significant at the P < 0.05 level. Data are expressed as mean ± standard error of the mean (SEM, representing the pooled SEM in the model). The FA concentration in the meat was calculated as follows, where 0.945 is the conversion factor for poultry meat [28]: FA in meat (mg/100 g) = [total lipid (%) × 0.945 × FA (% of total FA in meat)] × 10. RESULTS AND DISCUSSION Fatty acid Composition of Diets The major FA in the experimental diets of growers and finishers are listed in Tables 2 and 3, respectively. In the growers, the percentage of n-6 PUFA decreased with increasing level of TO substitution. According to the FA profiles, the TO6 diet (in both growing and finishing phases) yielded a high C16:0 content but a lower percentage of EPA and DHA than the TO4 treatment. As the LO level increased, the percentages of C16:0, C18:1n-9, and C18:2n-6 FA steadily declined, while the ALA content increased dramatically. Table 2. Major fatty acids (g/100 g total fatty acids) of experimental diets in the growing phase. Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 2. Major fatty acids (g/100 g total fatty acids) of experimental diets in the growing phase. Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 3. Major fatty acids (g/100 g total fatty acids) of experimental diets in the finishing period. Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 3. Major fatty acids (g/100 g total fatty acids) of experimental diets in the finishing period. Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Long-chain n-3 PUFA in the TO treatments were highly susceptible to lipid peroxidation. Peroxidation was detrimental in the TO6 diet. The TO4 and TO2 diets included 2 and 4% RBO, respectively. The vitamin E components (tocopherols and tocotrienols, present at ∼0.1 to 0.14%) and oryzanol (0.9 to 2.9%) in RBO [29] exhibit antioxidant properties that might protect the long-chain n-3 PUFA in the TO2 and TO4 diets. Unfortunately, the oxidative stabilities and antioxidant capacities of the diets were not measured in the present study. Growth Performance The mortality during the experimental period was 0.36%. Overall, the birds on diet TO6 demonstrated lower BW than the control and other oil-supplemented birds (Table 4). The reduction in BW among treatments was mainly caused by the difference between the TO and LO groups after 35 d of feeding (P < 0.05 by contrast analysis). Throughout the experiment, the accumulative feed intake was similar in all treatments. The FCR was significantly higher in chickens on the TO6 diet (P < 0.01) than in chickens on the other diets (the exception was LO2). Consistent with this finding, many other studies reported no difference in the growth performance parameters of broilers fed with LO or TO [30–36]. The FCR was unaffected by LO supplementation, but was increased by TO supplementation (P < 0.05 by contrast analysis). Table 4. Initial body weight (d 21, g), final BW (d 84, g), feed intake (FI, g/b), and FCR of chickens supplemented with tuna oil or linseed oil. Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 a,bDifferent superscripts in the same column denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). View Large Table 4. Initial body weight (d 21, g), final BW (d 84, g), feed intake (FI, g/b), and FCR of chickens supplemented with tuna oil or linseed oil. Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 a,bDifferent superscripts in the same column denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). View Large The reduced performance of the chickens on the TO6 diet may be explained by the oxidation of the n-3 long-chain PUFA. Oxidation releases free radicals that can alter the protein quality, and possibly induce loss of amino acids. Engberg, et al. [37] also reported that oxidized oil can decrease the nutrient content of the feed and suppress growth performance by reacting with proteins, lipids, and fat-soluble vitamins, even forming toxic products. These effects are often suppressed by increasing the intake of vegetable oils containing natural antioxidants [38]; therefore, supplementation with 6% TO alone reduced the growth performance. In contrast, adding 8.2% LO or TO to a broiler chicken diet maintains the daily weight gain and FCR of the birds [7], possibly by introducing an antioxidant (0.02% butylhydroxytoluol). Thus, including TO (6%) in the diet without an appropriate amount and type of antioxidant can negatively influence the growth performance. In another study, the monocytes and the bursa of Fabricius weights were reduced in chickens fed with 60 g/kg of fish oil, implying that fish oil suppresses some aspects of the immune response; however, the infection risk during fish oil consumption was not evaluated [39]. Although no disease incidences were observed in the present study, 6% TO might have compromised the birds’ defense systems. Furthermore, eliciting an effective immune response is costly [40]. In other words, the performance of the TO6 chickens might have declined because this group dedicated more bodily resources to immunity than the other groups. pH, Water-holding Capacity and Shear Force of Meat Oil supplementation did not affect the pH or shear forces of the meat (Table 5). The pH (measured at 45 min and 24 h) was expected to change during the aging process. Instead, the pH plateaued, possibly affected by the low glycogen level and the increased radical oxygen species, oxidation stress, and muscle catabolism [41]. Table 5. pH, water-holding capacity, and shear force of breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 a,bDifferent superscripts in the same row denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2WBS: Warner–Bratzler shear force (kgf/0.5 cm2). View Large Table 5. pH, water-holding capacity, and shear force of breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 a,bDifferent superscripts in the same row denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2WBS: Warner–Bratzler shear force (kgf/0.5 cm2). View Large The water-holding capacity, determined by the drip and boiling losses, is an important parameter in whole meat. The drip loss from breast and thigh meat was unaffected by the oil supplementations, possibly because the unsaturated FA concentrations were relatively high in all treatments. The cooking loss of breast meat was highest in the LO6 treatment (P < 0.05), and was low in the control and TO2 treatments. This tendency seems to be related to the PUFA level in the diet. The decreased water-holding capacity of meat from chickens consuming a PUFA-rich diet might be caused by increased oxidation of the cell membranes. In fact, the oxidative defense system of muscle directly affects the water-holding capacity [42]. Therefore, by adding an antioxidant to the diets in the present study, we could preserve the integrity of the muscle cell membranes and retain the water entrapped in the meat. This idea concurs with previous studies [43, 44], in which supplementation with fish oil and LO reduced the water-holding capacity of broiler meat. Meat Cholesterol In general, the cholesterol concentrations in the breast and thigh meat were unaffected by the types and levels of oil supplements in the chicken diet (Figure 1). Although the cholesterol content of breast meat was lower in the control group (P < 0.05) than in the groups supplemented with TO or LO (orthogonal contrast analysis), this trend was absent in the thigh meat. The cholesterol content was lower in the breast meat (40.73 to 48.73 mg/100 g meat) than in the thigh meat (63.77 to 76.01 mg/100 g meat). The cholesterol concentration in raw meat was unaffected by all treatments. Dinh, et al. [45] reported contradictory results among their reviewed studies, suggesting that unless there are pronounced changes in the muscle structure and composition, the cholesterol content is unlikely to change. The cholesterol content of breast meat was higher in our study than in Jaturasitha, et al. [46], who found only 10.9 to 15.1 mg/100 g meat. However, in the thigh meat of crossbred chickens, Jaturasitha et al.’s results were similar to ours. The difference might have been caused by the very low fat percentage in the breast meat of their crossbred chickens (0.43 to 0.59%). The cholesterol contents also ranged more widely in the present study than in the Thai indigenous crossbred chickens studied by Molee, et al. [47]. However, the cholesterol levels were lower in the present study of slow-growing chickens than in the broiler chicken meat reported by Dinh, et al. [45]. Figure 1. View largeDownload slide Cholesterol content (mg/100 g; mean ± SEM; n = 4/treatment) in breast (dotted line) and thigh (solid line) meats of chickens supplemented with tuna oil or linseed oil as a substitute for rice bran oil (P > 0.05). Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). Figure 1. View largeDownload slide Cholesterol content (mg/100 g; mean ± SEM; n = 4/treatment) in breast (dotted line) and thigh (solid line) meats of chickens supplemented with tuna oil or linseed oil as a substitute for rice bran oil (P > 0.05). Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). Fatty Acid Profile of Chicken Meat The total lipid contents in the breast meat samples ranged from 1.68 to 2.94 g/100 g fresh meat. The intramuscular fat content is strongly affected by the breed, rearing system, and age of the chickens [48]. The total lipid contents in breast meat were higher in the present study than in some previous reports [10, 49], but were consistent with other studies; particularly, with total breast lipid contents of 2.88% in 16-week-old Thai indigenous chickens [50], 2.82% in 12-week-old Thai crossbred chickens [51], and from 1.23 ± 0.07 [52] to 2.24 ± 0.17 [53] in 10-week-old Korat meat chickens. The thigh meat contained approximately twice the total lipid content in the breast meat. Most of the FA present in the breast (Table 6) and thigh (Table 7) samples significantly differed (P < 0.05) between pairs of treatments (C18:0 in breast meat was an exception). In both types of meat, the highest levels of n-6 PUFA were found in the control. The C20:4n-6 (AA) deposition in the breast meat was lower (P < 0.001) in chickens supplemented with n-3 PUFA than in chickens fed the control diet. The control diets based on corn-soybean meal supplemented with RBO contained approximately 70% C18:1n-9 and C18:2n-6 FA; subsequently, the meat was modified to maximize the levels of these FA. In the present study, the proportion of AA in the meat of chickens supplemented with TO or LO was almost half that in the control group. This is desirable because AA is a precursor of prostaglandin E2, a very active pro-inflammatory agent. Similar results were reported by Shin, et al. [54], who fed Cobb × Ross male broilers with n-3 PUFA or with animal and vegetable oils for 9 wk, and by Kartikasari, et al. [55], who found that increasing the dietary ALA intake reduced the AA content of chicken meat. Table 6. Major fatty acid profiles (g/100 g total FA) of skinless breast meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 a–dDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 6. Major fatty acid profiles (g/100 g total FA) of skinless breast meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 a–dDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 7. Major fatty acid profiles (g/100 g total FAs) of skinless thigh meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 a–fDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 7. Major fatty acid profiles (g/100 g total FAs) of skinless thigh meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 a–fDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large The level of dietary TO was also positively correlated with the total n-3 PUFA content (P < 0.05) of the meat. In the polynomial contrast analysis, the levels of EPA, DHA, and total n-3 PUFA in breast meat (quadratic, P < 0.001) and thigh meat (cubic, P < 0.001) significantly depended on the dietary TO. Among the 6 experimental treatments, TO6 produced the highest SFA content in thigh meat, but the n-3 PUFA contents were similar in the TO6 and TO2 treatments. In both types of meat, the TO4 treatment increased the EPA and DHA contents more effectively than the TO2 and TO6 treatments (Figure 2). If the TO6 were supplemented with an effective antioxidant, it would protect the n-3 PUFA in the feed from lipid oxidation. In this case, the EPA and DHA levels of the chicken meat are projected to be higher in TO6 than in TO4. Figure 2. View largeDownload slide Effect of dietary tuna oil on n-3 PUFA profiles in breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). Figure 2. View largeDownload slide Effect of dietary tuna oil on n-3 PUFA profiles in breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). The ALA, DHA, and total n-3 PUFA levels in both breast and thigh meat significantly depended on the dietary LO (linear, P < 0.05). The proportion of ALA was higher in thigh than in breast meat (Figure 3). The EPA and DHA contents were higher in the meat of the LO-fed chickens than in meat from the control group. Figure 3. View largeDownload slide Effects of dietary linseed oil on n-3 PUFA profiles of breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). Figure 3. View largeDownload slide Effects of dietary linseed oil on n-3 PUFA profiles of breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). The amount of FA in meat depends on the amounts of FA ingested in the diet, the antioxidative status of the FA, and the FA synthesis in the liver [56]. The conversion efficiency from ALA to EPA and DHA also depends on the ratio of the ingested LA and ALA [57]. In the present study, the ALA/LA ratio in the chickens’ diet increased from 0 to 6% LO, and (to a lesser extent) from 0 to 6% TO. Therefore, the conversion of ALA to its derivatives was nutritionally valuable in the LO-treated group. This result contradicts Lopez-Ferrer, et al. [44], who reported that ALA conversion is nutritionally meaningless; however, their research was conducted on broiler (Cobb) chickens. In addition, medium-growing chickens exhibit higher Δ6 and Δ5 desaturase activities than fast-growing chickens; consequently, the long-chain n-3 PUFA content of the breast meat is higher in medium-growing birds than in fast-growing birds fed the same diet [3]. In the present study, the EPA and DHA contents of the intramuscular fat were higher in the breast than in the thigh muscle, consistent with Zuidhof, et al. [58]. Meanwhile, the ALA content was considerably higher in thigh meat than in breast meat. ALA is mainly deposited in the triacylglycerol fraction of meat [59], which is large in thigh meat. In contrast, the breast is dominated by phospholipid. The n-6/n-3 ratios in the breast and thigh meats were significantly different (P < 0.0001), and were highest in the control. In the breast meats of the groups supplemented with TO or LO, the n-6/n-3 ratios were below 4, and were lowest in TO4. In the thigh meat, the n-6/n-3 ratio was lowest in the LO6 treatment (P < 0.05), and similar in the LO4 and TO4 treatments. Because the total lipid content in the meat was not significantly different among treatments, the mean total lipid among all treatments was used in the calculations. Slow-growing chickens receiving the TO2 and TO4 diets produced 252.88 mg and 377.53 mg DHA per 100 g raw breast, respectively. The DHA contents were lower in thigh meat than in breast meat, being 293.92 mg/100 g raw meat in the TO4 diet and approximately 140 mg/100 g meat in the TO2 and TO6 diets (Table 8). This implies that the n-3 PUFA amounts accumulated by slow-growing chickens are nutritionally valuable for human consumption. As noted by the European Food Safety Authority (EFSA), DHA contributes to the maintenance of normal brain function and vision. The EFSA recommends a daily DHA intake of 250 mg to elicit the beneficial effect. The LO treatment also increased the amount of ALA in the meat. However, only the thigh meat of chickens consuming the LO6 diet contained over 600 mg ALA/100 g meat, reaching the threshold of “high in n-3 PUFA” meat defined by the Commission Regulations (EU) 1924/2006 [11] and 432/2012. Although chickens fed with LO produced significant amounts of EPA and DHA (especially in the breast meat), these FA were predominantly supplied by TO. Table 8. Amounts (mg/100 g fresh meat) of some major n-3 fatty acids and total n-3 PUFA in breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). nd: Not detectable. View Large Table 8. Amounts (mg/100 g fresh meat) of some major n-3 fatty acids and total n-3 PUFA in breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). nd: Not detectable. View Large CONCLUSIONS AND APPLICATIONS The main findings of the study are summarized below. Adding 6% tuna oil to the diet of slow-growing chickens reduced the final BW and increased the FCR. The breast meat of chickens fed with 6% linseed oil showed the highest boiling loss. Diets rich in n-3 PUFA oils did not significantly affect the meat cholesterol content. Feeding with 4% tuna oil boosted the DHA amounts (>250 mg/100 g fresh meat) in both breast and thigh meats. Supplementing the chicken diet with TO or LO (≥2%) enriched the PUFA content of the breast meat, achieving the “high in n-3 PUFA” requirement of the EU’s food market. Thigh meat supplemented with at least 2% TO or 6% LO reached the thresholds of 80 mg EPA+DHA/100 g meat and 600 mg ALA/100 g meat, respectively; thus, they qualify as “high in n-3 PUFA” in the EU’s food market. Footnotes Primary Audience: Nutritionists, Researchers, and Producers REFERENCES AND NOTES 1. Stark K. D. , Van Elswyk M. E. , Higgins M. 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The Study of carcass yields and meat quality in crossbred native chicken (Chee) . Agriculture and Agricultural Science Procedia 11 : 84 – 89 . Google Scholar CrossRef Search ADS 52. Yongsawatdigul J. , Molee A. . 2016 . Suranaree Univ. of Tech., NakhonRatchasima, Thailand. Personal communication . 53. Pongjanla S. , Suttinon T. , Molee A. , Yongsawatdigul J. . 2014 . Comparative study on meat quality of Korat chicken and commercial broiler in The 5th Meat Science and Technology: Meat Production in the Global Trade Competition, Faculty of Agricutural Technology, KMITL . 54. Shin D. , Choi S. H. , Go G. , Park J. H. , Narciso-Gaytán C. , Morgan C. A. , Smith S. B. , Sánchez-Plata M. X. , Ruiz-Feria C. A. . 2012 . Effects of dietary combination of n-3 and n-9 fatty acids on the deposition of linoleic and arachidonic acid in broiler chicken meats . Poult. Sci. 91 : 1009 – 1017 . Google Scholar CrossRef Search ADS PubMed 55. Kartikasari L. R. , Hughes R. J. , Geier M. S. , Makrides M. , Gibson R. A. . 2012 . Dietary alpha-linolenic acid enhances omega-3 long chain polyunsaturated fatty acid levels in chicken tissues . Prostaglandins, Leukotrienes Essent. Fatty Acids 87 : 103 – 109 . Google Scholar CrossRef Search ADS 56. Farhoomand P. , Checaniazer S. . 2009 . Effects of graded levels of dietary fish oil on the yield and fatty acid composition of breast meat in broiler chickens . The Journal of Applied Poultry Research . 18 : 508 – 513 . Google Scholar CrossRef Search ADS 57. Harnack K. , Andersen G. , Somoza V. . 2009 . Quantitation of alpha-linolenic acid elongation to eicosapentaenoic and docosahexaenoic acid as affected by the ratio of n6/n3 fatty acids . Nutr Metab (Lond) . 6 : 8 . Google Scholar CrossRef Search ADS PubMed 58. Zuidhof M. , Betti M. , Korver D. , Hernandez F. , Schneider B. , Carney V. , Renema R. . 2009 . Omega-3-enriched broiler meat: 1. Optimization of a production system . Poult. Sci . 88 : 1108 – 1120 . Google Scholar PubMed 59. Betti M. , Perez T. I. , Zuidhof M. J. , Renema R. A. . 2009 . Omega-3-enriched broiler meat: 3. Fatty acid distribution between triacylglycerol and phospholipid classes . Poult. Sci. 88 : 1740 – 1754 . Google Scholar CrossRef Search ADS PubMed Acknowledgments We gratefully acknowledge the mainly support of the Thailand Research Fund (TRF) and the Suranaree University of Technology (SUT) under the project “Establishment of ‘Korat Meat Chicken’ Strain for Small and Micro Community Enterprise Production.” We also highly appreciate the “PhD Scholarship for Asean Countries” program of SUT for partly supporting this research. © 2017 Poultry Science Association Inc. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Poultry Research Oxford University Press

Linseed oil or tuna oil supplementation in slow-growing chicken diets: Can their meat reach the threshold of a “high in n-3 polyunsaturated fatty acids” product?

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Oxford University Press
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© 2017 Poultry Science Association Inc.
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1056-6171
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1537-0437
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10.3382/japr/pfy010
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Abstract

SUMMARY A strategy for enriching the meat of slow-growing chickens with n-3 fatty acids from tuna oil (TO) or linseed oil (LO) is proposed. The effects of TO or LO supplementation on the growth performance of the chickens and the quality, cholesterol content, and fatty acid composition of the meat were examined. A total of 560 21-day-old mixed-sex Thai indigenous crossbred chickens was assigned to a completely randomized design with 7 treatment diets and 4 replicates. The control group consumed a basal diet of corn-soybean meal supplemented with rice bran oil (RBO; 6%). In the experimental diets, RBO was replaced with 2, 4, or 6% TO (TO2, TO4, and TO6) or with 2, 4, or 6% LO (LO2, LO4, and LO6). All groups received 6% added oil. The TO6 diet lowered the final BW and FCR. The boiling loss of breast meat was highest in LO6 and differed from the losses in the control and TO2 groups. Meat from TO4 and LO6 yielded the lowest n-6/n-3 ratio. The alpha-linolenic acid (ALA) content linearly increased across the LO group. The n-3 fatty acid accumulation in the slow-growing chickens was nutritionally valuable for human consumption. Breast meat from TO2 and TO4 provided >250 mg docosahexaenoic acid (DHA) per 100 g fresh meat. Thigh meat from at least 2% TO or 6% LO contained >80 mg (eicosapentaenoic acid + DHA)/100 g meat and 600 mg ALA/100 g meat, respectively, reaching the “high in n-3 polyunsaturated fatty acids” threshold in dietary recommendations. DESCRIPTION OF PROBLEM The beneficial effects of n-3 polyunsaturated fatty acids (PUFA)—maintaining heart health, protecting against cancer and birth defects, and offsetting the symptoms of diabetes—have been known for many decades. Low levels of eicosapentaenoic acid (C20:5n-3; EPA) and very low levels of docosahexaenoic acid (C22:6n-3; DHA), which have been recently observed in the blood of people throughout most of the world, are associated with increased risk of cardiovascular-related mortality [1]. Therefore, increasing n-3 PUFA consumption by supplements or functional food is recommended. De Smet and Vossen [2] reported that poultry more easily responds to dietary n-3 PUFA supplementation than pork, lamb, or beef. Moreover, the conversion of alpha-linolenic acid (C18:3n-3; ALA) to long-chain n-3 PUFA is better in slow- and medium-growing birds than in fast-growing birds fed the same diet [3]. In certain regions of the world, consumers prefer the tasty, chewy meat from native chickens to the meat from commercially bred broilers [4]. The emergent market of functional foods has inspired the production of slow-growing chicken meat with a lower fat content and a healthier fatty acid (FA) profile for this niche market. In tropical Asia, non-food grade tuna oil (TO) and rice bran oil (RBO) are readily available in large amounts [5]. Such affordable oil supplements in slow-growing chicken diets might enable small and medium entrepreneurs to produce value-added meat. However, tuna has markedly declined in the global marine vertebrate population [6]. A possibly better alternative is linseed oil (LO), which is rich in ALA. In fact, chickens fed on diets supplemented with LO or fish oil yielded similar proportions of total n-3 PUFA in their breast meat, and the LO-fed chickens yielded higher n-3 PUFA content, especially ALA, in their thigh meat [7]. However, in male Cobb chickens subjected to transient high-temperature stress, fish oil (8.0%) caused higher mortality than palm oil or no added fat [8]. Hence, the level of fish oil in chickens’ diets should be reduced in tropical conditions. The fat content is lower in slow-growing chickens than in commercial broilers [9, 10]. Like turkey meat [11], slow-growing chicken meat rarely achieves the “source of n-3 PUFA” threshold in dietary recommendations. To address this problem, the present study investigated an enrichment strategy for slow-growing chicken meat, in which part of the dietary RBO is replaced with TO or LO. After applying this strategy, the n-3 PUFA content in the meat of slow-growing chickens is expected to meet the health recommendations of the European Union, while the growth performance and other quality characteristics are only marginally affected. MATERIALS AND METHODS Birds and Housing All procedures in the present study were approved by the Ethics Committee on Animal Use of the Suranaree University of Technology, Thailand. The chickens were Thai indigenous crossbreeds called “Korat meat chickens.” The chicks were vaccinated against Marek's disease at the hatchery, against Newcastle disease and infectious bronchitis on d 7 and 21, and against Gumboro disease on d 14. After hatching, the chickens were kept together until 21 d of age (an average BW of 271.68 ± 38.07 g), then transferred to the experimental pens. From d 1 to 21, the chicks were fed a corn-soybean meal-based diet (21% CP and 3,100 kcal ME/kg). The total FA content of this diet comprised 41.07% n-6 PUFA, 3.51% n-3 PUFA, 32.80% monounsaturated fatty acid (MUFA), and 22.63% saturated fatty acid (SFA). In all treatments, the birds were reared on floor pens (8 birds/m2) under similar environmental and management conditions until 84 d of age. The floor pens were layered with rice hulls (depth 5 cm) as bedding. Feed and water were freely available to all chickens. Experimental Design and Diets The experimental model was a completely randomized design, which included 7 treatment diets, 4 replicates, and 20 21-day-old mixed-sex chicks per replicate. The control diet was a basal formulation of corn-soybean meal containing 6% RBO. In the treatment diets, part of the RBO content was substituted with 2, 4, or 6% TO or LO. Note that the total oil content of all diets was 6%. All experimental diets were formulated with equal nitrogen levels and provided 3,100 kcal ME/kg. The CP was 19% for the grower diet (d 22 to 42) and 17% for the finisher diet (d 43 to 84) (see Table 1). Feed-grade oils were used in all experimental diets. RBO [12] is rich in C18:1n-9 (42.31%) and C18:2n-6 (LA; 32.77%) but its ALA levels are very low (1.45%). DHA is predominant in TO [13] (30.38%), while ALA constitutes 57.83% of LO [14]. Table 1. Compositions and calculated nutrient contents of grower and finisher diets (g/100 g diet, as-fed basis). Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 1Type and level of oil depends on the treatment. The diet was supplemented with rice bran oil and either tuna oil or linseed oil at 0, 2, 4, or 6%. The total amount of added oil in all treatments (including the control) was 6%. 2Premix (0.5%) provided the following nutrients per kilogram of diet: 15,000 IU vitamin A; 3,000 IU vitamin D3; 25 IU vitamin E; 5 mg vitamin K3; 2 mg vitamin B1; 7 mg vitamin B2; 4 mg vitamin B6; 25 μg vitamin B12; 11.04 mg pantothenic acid; 35 mg nicotinic acid; 1 mg folic acid; 15 μg biotin; 250 mg choline chloride; 1.6 mg Cu; 60 mg Mn; 45 mg Zn; 80 mg Fe; 0.4 mg I; 0.15 mg Se. View Large Table 1. Compositions and calculated nutrient contents of grower and finisher diets (g/100 g diet, as-fed basis). Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 Grower Finisher Items (d 22 to 42) (d 43 to 84) Soybean meal (44% CP) 33.55 26.55 Corn 50.36 51.50 De-oil rice bran 6.11 12.48 Added oil1 6.00 6.00 DL-Methionine 0.25 0.19 L-Lysine 0.13 0.10 L-Threonine 0.10 0.06 Salt 0.35 0.28 CaCO3 1.57 1.42 Dicalcium phosphate 1.08 0.92 Premix2 0.50 0.50 Calculated nutrients (%) Crude protein 19.00 17.00 Crude fat 8.13 8.24 1Type and level of oil depends on the treatment. The diet was supplemented with rice bran oil and either tuna oil or linseed oil at 0, 2, 4, or 6%. The total amount of added oil in all treatments (including the control) was 6%. 2Premix (0.5%) provided the following nutrients per kilogram of diet: 15,000 IU vitamin A; 3,000 IU vitamin D3; 25 IU vitamin E; 5 mg vitamin K3; 2 mg vitamin B1; 7 mg vitamin B2; 4 mg vitamin B6; 25 μg vitamin B12; 11.04 mg pantothenic acid; 35 mg nicotinic acid; 1 mg folic acid; 15 μg biotin; 250 mg choline chloride; 1.6 mg Cu; 60 mg Mn; 45 mg Zn; 80 mg Fe; 0.4 mg I; 0.15 mg Se. View Large Sampling and Measurements Growth performance. The weight gain and FCR values were calculated from the BW and feed intake, which were monitored once a wk in each pen. The occurrence of mortality also was recorded. Sampling. At 84 d of age, chickens weighing within 10% of the mean of the experimental unit were processed after a 12-hour feed withdrawal period. After the selection, 112 birds were transported to the university slaughterhouse, where they were stunned by electricity, scalded, and de-feathered by machine, then manually eviscerated. The functional properties (pH, drip loss, cooking loss, and shear force) were measured in meat samples from 2 chickens (one male and one female) per experimental unit. Breast and thigh meats were sampled from 2 other chickens (one male and one female per pen), then stored at –20°C until required for FA profiling and cholesterol content analysis. pH Measurement. The pH of the breast fillet was measured directly by a pH meter with a precision of 0.01 pH units [15] coupled to a probe inserted into the center of the pectoralis major muscle. The probe depth was 0.5 to 1.0 cm. Water-Holding Capacity. After chilling for 24 h, the water-holding capacity was determined as the drip loss (when samples were placed in an airtight container and hung in a chilled room for 24 h at 4°C) and cooking loss (when samples were boiled in a water bath in open plastic bags until the internal temperature reached 80°C). Shear Force Measurement. The peak shear forces of 3 subsamples (2.0 cm × 1.0 cm × 0.5 cm) were measured by a texture analyzer [16] equipped with a Warner–Bratzler shear force apparatus. The crosshead speed was set at 20 cm/min [17]. Fatty Acid Analysis. The lipids were extracted from approximately 5 g of each muscle sample [18], and 20 to 25 mg of the extracted fat were then methylated [19]. The fatty acid methyl esters (FAME) were analyzed using gas chromatography [20] with a capillary column [21] and a flame ionization detector. The carrier gas was helium at a flow rate of 0.95 ml/min. The injector and detector temperature was 260°C. The column temperature was raised from its initial 70°C to 175°C at 13°C/min, and finally raised to 240°C at 4°C/min [22]. Meat Cholesterol. The cholesterol content was measured in the raw breast and thigh meat [23]. The cholesterol was analyzed using gas chromatography [24] with a capillary column [25] and a flame ionization detector. The temperatures of the injector and detector were 260 and 300°C, respectively. Separation was carried out isocratically at 300°C with helium gas flowing at 1 mL/min [26]. Statistical Analysis and Calculations Analysis of variance was performed by a GLM procedure for completely randomized design. The procedure was implemented in SAS University Edition [27] using the pen mean as the experimental unit. Significant differences among the treatment means were determined by F-test and assessed by Tukey's multiple comparison tests. Differences between oil sources and control or between different types of added oils were tested using orthogonal contrasts, whereas the effects of different levels of TO or LO were tested by polynomial contrasts. Overall differences among the treatment means were considered significant at the P < 0.05 level. Data are expressed as mean ± standard error of the mean (SEM, representing the pooled SEM in the model). The FA concentration in the meat was calculated as follows, where 0.945 is the conversion factor for poultry meat [28]: FA in meat (mg/100 g) = [total lipid (%) × 0.945 × FA (% of total FA in meat)] × 10. RESULTS AND DISCUSSION Fatty acid Composition of Diets The major FA in the experimental diets of growers and finishers are listed in Tables 2 and 3, respectively. In the growers, the percentage of n-6 PUFA decreased with increasing level of TO substitution. According to the FA profiles, the TO6 diet (in both growing and finishing phases) yielded a high C16:0 content but a lower percentage of EPA and DHA than the TO4 treatment. As the LO level increased, the percentages of C16:0, C18:1n-9, and C18:2n-6 FA steadily declined, while the ALA content increased dramatically. Table 2. Major fatty acids (g/100 g total fatty acids) of experimental diets in the growing phase. Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 2. Major fatty acids (g/100 g total fatty acids) of experimental diets in the growing phase. Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 Growing diet1 (d 22 to 42) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.67 20.24 22.04 30.57 16.06 12.15 10.06 C18:0 5.37 6.16 9.39 11.94 4.43 3.46 4.60 C18:1n-9 35.05 30.00 26.19 22.46 31.02 26.57 21.64 C18:2n-6 34.24 28.35 20.32 15.82 31.82 29.26 24.79 C18:3n-3 1.69 1.43 1.13 1.01 13.84 27.51 36.35 C20:5n-3 –2 1.07 1.66 0.57 – – – C22:6n-3 – 6.27 9.62 2.49 – – – SFA 28.38 31.21 38.50 52.54 22.72 16.35 16.92 MUFA 35.60 31.53 28.61 27.03 31.50 26.70 21.80 PUFA 36.02 37.25 32.89 20.43 45.79 56.95 61.28 n-6 34.34 28.48 20.47 16.06 31.95 29.44 24.93 n-3 1.69 8.77 12.42 4.37 13.84 27.51 36.35 n-6/n-3 20.33 3.25 1.65 3.67 2.31 1.07 0.69 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 3. Major fatty acids (g/100 g total fatty acids) of experimental diets in the finishing period. Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Table 3. Major fatty acids (g/100 g total fatty acids) of experimental diets in the finishing period. Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 Finishing diet1 (d 43 to 84) Items Control TO2 TO4 TO6 LO2 LO4 LO6 C16:0 19.34 19.92 20.75 27.35 15.84 12.60 11.92 C18:0 3.54 4.91 5.95 7.78 3.42 4.78 6.03 C18:1n-9 37.37 31.06 25.53 23.31 32.23 26.00 20.88 C18:2n-6 35.65 29.46 23.70 18.08 31.77 27.18 21.48 C18:3n-3 1.62 1.30 1.23 0.96 14.25 26.36 32.88 C20:5n-3 –2 0.48 0.99 0.62 – – – C22:6n-3 – 6.26 12.92 7.00 – – – SFA 24.79 29.78 32.92 44.52 21.20 20.09 24.31 MUFA 37.94 32.62 28.11 27.70 32.77 26.37 21.33 PUFA 37.27 37.60 38.97 27.77 46.03 53.54 54.36 n-6 35.65 29.56 23.84 18.27 31.77 27.18 21.48 n-3 1.62 8.04 15.13 9.50 14.25 26.36 32.88 n-6/n-3 21.97 3.68 1.58 1.92 2.23 1.03 0.65 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2– = Not detected. View Large Long-chain n-3 PUFA in the TO treatments were highly susceptible to lipid peroxidation. Peroxidation was detrimental in the TO6 diet. The TO4 and TO2 diets included 2 and 4% RBO, respectively. The vitamin E components (tocopherols and tocotrienols, present at ∼0.1 to 0.14%) and oryzanol (0.9 to 2.9%) in RBO [29] exhibit antioxidant properties that might protect the long-chain n-3 PUFA in the TO2 and TO4 diets. Unfortunately, the oxidative stabilities and antioxidant capacities of the diets were not measured in the present study. Growth Performance The mortality during the experimental period was 0.36%. Overall, the birds on diet TO6 demonstrated lower BW than the control and other oil-supplemented birds (Table 4). The reduction in BW among treatments was mainly caused by the difference between the TO and LO groups after 35 d of feeding (P < 0.05 by contrast analysis). Throughout the experiment, the accumulative feed intake was similar in all treatments. The FCR was significantly higher in chickens on the TO6 diet (P < 0.01) than in chickens on the other diets (the exception was LO2). Consistent with this finding, many other studies reported no difference in the growth performance parameters of broilers fed with LO or TO [30–36]. The FCR was unaffected by LO supplementation, but was increased by TO supplementation (P < 0.05 by contrast analysis). Table 4. Initial body weight (d 21, g), final BW (d 84, g), feed intake (FI, g/b), and FCR of chickens supplemented with tuna oil or linseed oil. Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 a,bDifferent superscripts in the same column denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). View Large Table 4. Initial body weight (d 21, g), final BW (d 84, g), feed intake (FI, g/b), and FCR of chickens supplemented with tuna oil or linseed oil. Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 Treatment1 BW d 21 (g) BW d 84 (g) FI (g/b) FCR Control 266.19 1,582.51a 3,741.77 2.85b TO2 264.75 1,570.75a 3,839.09 2.95b TO4 270.50 1,562.5a 3,829.57 2.96b TO6 264.00 1,378.95b 3,764.90 3.39a LO2 265.38 1,577.25a 3,964.36 3.02a,b LO4 264.75 1,525.88a 3,779.76 3.01b LO6 268.13 1,607.50a 3,867.27 2.89b SEM 6.81 62.66 155.93 0.16 P-value 0.831 0.001 0.493 0.002 P-value of contrast Control vs. Tuna oil 0.955 0.042 0.449 0.012 Control vs. Linseed oil 0.979 0.737 0.168 0.187 Tuna oil vs. Linseed oil 0.906 0.017 0.362 0.062 a,bDifferent superscripts in the same column denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). View Large The reduced performance of the chickens on the TO6 diet may be explained by the oxidation of the n-3 long-chain PUFA. Oxidation releases free radicals that can alter the protein quality, and possibly induce loss of amino acids. Engberg, et al. [37] also reported that oxidized oil can decrease the nutrient content of the feed and suppress growth performance by reacting with proteins, lipids, and fat-soluble vitamins, even forming toxic products. These effects are often suppressed by increasing the intake of vegetable oils containing natural antioxidants [38]; therefore, supplementation with 6% TO alone reduced the growth performance. In contrast, adding 8.2% LO or TO to a broiler chicken diet maintains the daily weight gain and FCR of the birds [7], possibly by introducing an antioxidant (0.02% butylhydroxytoluol). Thus, including TO (6%) in the diet without an appropriate amount and type of antioxidant can negatively influence the growth performance. In another study, the monocytes and the bursa of Fabricius weights were reduced in chickens fed with 60 g/kg of fish oil, implying that fish oil suppresses some aspects of the immune response; however, the infection risk during fish oil consumption was not evaluated [39]. Although no disease incidences were observed in the present study, 6% TO might have compromised the birds’ defense systems. Furthermore, eliciting an effective immune response is costly [40]. In other words, the performance of the TO6 chickens might have declined because this group dedicated more bodily resources to immunity than the other groups. pH, Water-holding Capacity and Shear Force of Meat Oil supplementation did not affect the pH or shear forces of the meat (Table 5). The pH (measured at 45 min and 24 h) was expected to change during the aging process. Instead, the pH plateaued, possibly affected by the low glycogen level and the increased radical oxygen species, oxidation stress, and muscle catabolism [41]. Table 5. pH, water-holding capacity, and shear force of breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 a,bDifferent superscripts in the same row denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2WBS: Warner–Bratzler shear force (kgf/0.5 cm2). View Large Table 5. pH, water-holding capacity, and shear force of breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value Breast pH  pH 45 min 6.57 6.69 6.72 6.69 6.60 6.73 6.74 0.13 0.457  pH 24 h 6.71 6.50 6.77 6.62 6.52 6.45 6.47 0.16 0.074 Water-holding capacity (loss, % of total) Breast meat  Drip 10.51 9.30 8.48 10.04 8.73 10.19 8.81 1.25 0.210  Boiling 23.07b 22.88b 24.19a,b 23.61a,b 24.17a,b 25.02a,b 25.87a 1.09 0.010 Thigh meat  Drip 7.76 7.57 7.17 6.16 6.47 6.43 6.19 0.98 0.159  Boiling 28.60 26.48 25.25 25.07 26.82 29.15 30.69 2.99 0.157 Breast WBS2 3.10 2.61 2.04 3.20 3.18 3.50 2.91 0.79 0.245 Thigh WBS 1.42 1.51 1.22 1.45 1.21 1.41 1.51 0.36 0.821 a,bDifferent superscripts in the same row denote that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2WBS: Warner–Bratzler shear force (kgf/0.5 cm2). View Large The water-holding capacity, determined by the drip and boiling losses, is an important parameter in whole meat. The drip loss from breast and thigh meat was unaffected by the oil supplementations, possibly because the unsaturated FA concentrations were relatively high in all treatments. The cooking loss of breast meat was highest in the LO6 treatment (P < 0.05), and was low in the control and TO2 treatments. This tendency seems to be related to the PUFA level in the diet. The decreased water-holding capacity of meat from chickens consuming a PUFA-rich diet might be caused by increased oxidation of the cell membranes. In fact, the oxidative defense system of muscle directly affects the water-holding capacity [42]. Therefore, by adding an antioxidant to the diets in the present study, we could preserve the integrity of the muscle cell membranes and retain the water entrapped in the meat. This idea concurs with previous studies [43, 44], in which supplementation with fish oil and LO reduced the water-holding capacity of broiler meat. Meat Cholesterol In general, the cholesterol concentrations in the breast and thigh meat were unaffected by the types and levels of oil supplements in the chicken diet (Figure 1). Although the cholesterol content of breast meat was lower in the control group (P < 0.05) than in the groups supplemented with TO or LO (orthogonal contrast analysis), this trend was absent in the thigh meat. The cholesterol content was lower in the breast meat (40.73 to 48.73 mg/100 g meat) than in the thigh meat (63.77 to 76.01 mg/100 g meat). The cholesterol concentration in raw meat was unaffected by all treatments. Dinh, et al. [45] reported contradictory results among their reviewed studies, suggesting that unless there are pronounced changes in the muscle structure and composition, the cholesterol content is unlikely to change. The cholesterol content of breast meat was higher in our study than in Jaturasitha, et al. [46], who found only 10.9 to 15.1 mg/100 g meat. However, in the thigh meat of crossbred chickens, Jaturasitha et al.’s results were similar to ours. The difference might have been caused by the very low fat percentage in the breast meat of their crossbred chickens (0.43 to 0.59%). The cholesterol contents also ranged more widely in the present study than in the Thai indigenous crossbred chickens studied by Molee, et al. [47]. However, the cholesterol levels were lower in the present study of slow-growing chickens than in the broiler chicken meat reported by Dinh, et al. [45]. Figure 1. View largeDownload slide Cholesterol content (mg/100 g; mean ± SEM; n = 4/treatment) in breast (dotted line) and thigh (solid line) meats of chickens supplemented with tuna oil or linseed oil as a substitute for rice bran oil (P > 0.05). Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). Figure 1. View largeDownload slide Cholesterol content (mg/100 g; mean ± SEM; n = 4/treatment) in breast (dotted line) and thigh (solid line) meats of chickens supplemented with tuna oil or linseed oil as a substitute for rice bran oil (P > 0.05). Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). Fatty Acid Profile of Chicken Meat The total lipid contents in the breast meat samples ranged from 1.68 to 2.94 g/100 g fresh meat. The intramuscular fat content is strongly affected by the breed, rearing system, and age of the chickens [48]. The total lipid contents in breast meat were higher in the present study than in some previous reports [10, 49], but were consistent with other studies; particularly, with total breast lipid contents of 2.88% in 16-week-old Thai indigenous chickens [50], 2.82% in 12-week-old Thai crossbred chickens [51], and from 1.23 ± 0.07 [52] to 2.24 ± 0.17 [53] in 10-week-old Korat meat chickens. The thigh meat contained approximately twice the total lipid content in the breast meat. Most of the FA present in the breast (Table 6) and thigh (Table 7) samples significantly differed (P < 0.05) between pairs of treatments (C18:0 in breast meat was an exception). In both types of meat, the highest levels of n-6 PUFA were found in the control. The C20:4n-6 (AA) deposition in the breast meat was lower (P < 0.001) in chickens supplemented with n-3 PUFA than in chickens fed the control diet. The control diets based on corn-soybean meal supplemented with RBO contained approximately 70% C18:1n-9 and C18:2n-6 FA; subsequently, the meat was modified to maximize the levels of these FA. In the present study, the proportion of AA in the meat of chickens supplemented with TO or LO was almost half that in the control group. This is desirable because AA is a precursor of prostaglandin E2, a very active pro-inflammatory agent. Similar results were reported by Shin, et al. [54], who fed Cobb × Ross male broilers with n-3 PUFA or with animal and vegetable oils for 9 wk, and by Kartikasari, et al. [55], who found that increasing the dietary ALA intake reduced the AA content of chicken meat. Table 6. Major fatty acid profiles (g/100 g total FA) of skinless breast meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 a–dDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 6. Major fatty acid profiles (g/100 g total FA) of skinless breast meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 22.62b,c 22.70b 24.15a,b 25.34a 23.28a,b 22.20b,c 20.14c 0.99 <0.001 0.037 0.267 <0.001 C18:0 8.56 9.83 9.51 11.90 11.72 10.70 10.80 1.47 0.081 0.067 0.019 0.310 C18:1n-9 30.12a 24.63b 22.39b 23.90b 26.59a,b 23.93b 23.50b 1.68 <0.001 <0.001 <0.001 0.168 C18:2n-6 24.31a 20.50a,b 17.53b,c 16.02c 21.19a,b 23.97a 23.50a 1.73 <0.001 <0.001 0.228 <0.001 C20:4n-6 10.35a 4.76b 4.61b 5.43b 6.39b 5.36b 4.22b 1.24 <0.001 <0.001 <0.001 0.474 C18:3n-3 0.59c,d 1.20c,d 0.29d 0.28d 3.72b,c 6.46b 10.19a 1.21 <0.001 0.995 <0.001 <0.001 C20:5n-3 0.00c 1.02a–c 1.92a 1.69a 0.36b,c 1.19a–c 1.21a,b 0.47 0.001 <0.001 0.009 0.007 C22:6n-3 1.49d 11.27a,b 16.83a 10.07b,c 3.59d 4.12c,d 3.76d 2.39 <0.001 <0.001 0.155 <0.001 SFA 31.96b 34.26a,b 34.84a,b 39.73a 36.50a,b 33.43a,b 32.21b 2.74 0.015 0.025 0.263 0.074 MUFA 30.55a 25.40b 23.52b 26.21a,b 27.51a,b 24.15b 23.90b 2.01 0.004 0.001 0.001 0.872 PUFA 37.49a–c 40.33a–c 41.63a,b 34.06c 35.99b,c 42.41a,b 43.89a 2.75 0.001 0.512 0.087 0.094 n-6 35.41a 26.67b,c 22.60c,d 22.02d 28.21b 30.06b 28.53b 1.77 <0.001 <0.001 <0.001 <0.001 n-3 2.08d 13.66b 19.03a 12.03b,c 7.78c,d 12.36b,c 15.37a,b 2.17 <0.001 <0.001 <0.001 0.004 n-6/n-3 17.24a 2.14c,d 1.20d 1.91c,d 3.64b 2.46b,c 1.88c,d 0.47 <0.001 <0.001 <0.001 <0.001 a–dDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 7. Major fatty acid profiles (g/100 g total FAs) of skinless thigh meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 a–fDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large Table 7. Major fatty acid profiles (g/100 g total FAs) of skinless thigh meat from slow-growing chickens supplemented with tuna oil or linseed oil. Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 Treatment1 P-value of contrast Fatty acids Control TO2 TO4 TO6 LO2 LO4 LO6 SEM P-value C2 vs. TO C vs. LO TO vs. LO C16:0 18.46c 20.09b 20.54b 23.62a 17.24c,d 16.03d 14.01e 0.49 <0.001 <0.001 <0.001 <0.001 C18:0 7.59b 7.25b 8.79a,b 10.39a 7.85b 8.76a,b 9.46a,b 1.01 0.008 0.081 0.121 0.792 C18:1n-9 34.37a 32.08a,b 27.58c 30.47b,c 31.92a,b 28.02c 25.05d 1.03 <0.001 <0.001 <0.001 0.002 C18:2n-6 31.02a 28.27b,c 24.55d 19.12e 29.26a,b 28.60b,c 27.42c 0.78 <0.001 <0.001 <0.001 <0.001 C20:4n-6 4.21a 1.76b 2.84a,b 2.34b 2.81a,b 2.74a,b 2.44b 0.55 0.002 <0.001 0.001 0.174 C18:3n-3 1.08d 1.28d 1.00d 0.75d 6.66c 11.39b 17.04a 1.09 <0.001 0.923 <0.001 <0.001 C20:5n-3 0.03d 0.64b,c 1.25a 0.69b 0.07d 0.25c,d 0.67b,c 0.15 <0.001 <0.001 0.008 <0.001 C22:6n-3 0.49c 3.84b 7.97a 3.88b 1.22c 1.37c 1.46c 0.46 <0.001 <0.001 0.012 <0.001 SFA 26.93c,d 29.05b,c 31.44b 36.98a 25.91c,d 25.46c,d 24.20d 1.58 <0.001 <0.001 0.117 <0.001 MUFA 35.57a 34.53a 30.37b 35.55a 33.41a 29.32b 25.93c 1.15 <0.001 0.013 <0.001 <0.001 PUFA 37.50d 36.42d 38.19d 27.47e 40.68c 45.22b 49.87a 0.95 <0.001 <0.001 <0.001 <0.001 n-6 35.88a 30.66b 27.97c 22.08d 32.69b 31.89b 30.49b 1.06 <0.001 <0.001 <0.001 <0.001 n-3 1.62f 5.76d,e 10.22c 5.39e 7.99c,d 13.34b 19.38a 0.99 <0.001 <0.001 <0.001 <0.001 n-6/n-3 22.23a 5.40b 2.74c 4.22b 4.13b 2.41c 1.60c 0.55 <0.001 <0.001 <0.001 <0.001 a–fDifferent superscripts in the same row indicate that the means are significantly different at P < 0.05. 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). 2C: control. View Large The level of dietary TO was also positively correlated with the total n-3 PUFA content (P < 0.05) of the meat. In the polynomial contrast analysis, the levels of EPA, DHA, and total n-3 PUFA in breast meat (quadratic, P < 0.001) and thigh meat (cubic, P < 0.001) significantly depended on the dietary TO. Among the 6 experimental treatments, TO6 produced the highest SFA content in thigh meat, but the n-3 PUFA contents were similar in the TO6 and TO2 treatments. In both types of meat, the TO4 treatment increased the EPA and DHA contents more effectively than the TO2 and TO6 treatments (Figure 2). If the TO6 were supplemented with an effective antioxidant, it would protect the n-3 PUFA in the feed from lipid oxidation. In this case, the EPA and DHA levels of the chicken meat are projected to be higher in TO6 than in TO4. Figure 2. View largeDownload slide Effect of dietary tuna oil on n-3 PUFA profiles in breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). Figure 2. View largeDownload slide Effect of dietary tuna oil on n-3 PUFA profiles in breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). The ALA, DHA, and total n-3 PUFA levels in both breast and thigh meat significantly depended on the dietary LO (linear, P < 0.05). The proportion of ALA was higher in thigh than in breast meat (Figure 3). The EPA and DHA contents were higher in the meat of the LO-fed chickens than in meat from the control group. Figure 3. View largeDownload slide Effects of dietary linseed oil on n-3 PUFA profiles of breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). Figure 3. View largeDownload slide Effects of dietary linseed oil on n-3 PUFA profiles of breast (A) and thigh (B) meats from slow-growing chickens. Results are presented as means ± SEM (n = 4/treatment). The amount of FA in meat depends on the amounts of FA ingested in the diet, the antioxidative status of the FA, and the FA synthesis in the liver [56]. The conversion efficiency from ALA to EPA and DHA also depends on the ratio of the ingested LA and ALA [57]. In the present study, the ALA/LA ratio in the chickens’ diet increased from 0 to 6% LO, and (to a lesser extent) from 0 to 6% TO. Therefore, the conversion of ALA to its derivatives was nutritionally valuable in the LO-treated group. This result contradicts Lopez-Ferrer, et al. [44], who reported that ALA conversion is nutritionally meaningless; however, their research was conducted on broiler (Cobb) chickens. In addition, medium-growing chickens exhibit higher Δ6 and Δ5 desaturase activities than fast-growing chickens; consequently, the long-chain n-3 PUFA content of the breast meat is higher in medium-growing birds than in fast-growing birds fed the same diet [3]. In the present study, the EPA and DHA contents of the intramuscular fat were higher in the breast than in the thigh muscle, consistent with Zuidhof, et al. [58]. Meanwhile, the ALA content was considerably higher in thigh meat than in breast meat. ALA is mainly deposited in the triacylglycerol fraction of meat [59], which is large in thigh meat. In contrast, the breast is dominated by phospholipid. The n-6/n-3 ratios in the breast and thigh meats were significantly different (P < 0.0001), and were highest in the control. In the breast meats of the groups supplemented with TO or LO, the n-6/n-3 ratios were below 4, and were lowest in TO4. In the thigh meat, the n-6/n-3 ratio was lowest in the LO6 treatment (P < 0.05), and similar in the LO4 and TO4 treatments. Because the total lipid content in the meat was not significantly different among treatments, the mean total lipid among all treatments was used in the calculations. Slow-growing chickens receiving the TO2 and TO4 diets produced 252.88 mg and 377.53 mg DHA per 100 g raw breast, respectively. The DHA contents were lower in thigh meat than in breast meat, being 293.92 mg/100 g raw meat in the TO4 diet and approximately 140 mg/100 g meat in the TO2 and TO6 diets (Table 8). This implies that the n-3 PUFA amounts accumulated by slow-growing chickens are nutritionally valuable for human consumption. As noted by the European Food Safety Authority (EFSA), DHA contributes to the maintenance of normal brain function and vision. The EFSA recommends a daily DHA intake of 250 mg to elicit the beneficial effect. The LO treatment also increased the amount of ALA in the meat. However, only the thigh meat of chickens consuming the LO6 diet contained over 600 mg ALA/100 g meat, reaching the threshold of “high in n-3 PUFA” meat defined by the Commission Regulations (EU) 1924/2006 [11] and 432/2012. Although chickens fed with LO produced significant amounts of EPA and DHA (especially in the breast meat), these FA were predominantly supplied by TO. Table 8. Amounts (mg/100 g fresh meat) of some major n-3 fatty acids and total n-3 PUFA in breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). nd: Not detectable. View Large Table 8. Amounts (mg/100 g fresh meat) of some major n-3 fatty acids and total n-3 PUFA in breast and thigh meats. Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 Treatment1 Items Control TO2 TO4 TO6 LO2 LO4 LO6 Breast C18:3n-3 (ALA) 13.31 26.98 6.42 6.18 83.34 144.84 228.61 C20:5n-3 (EPA) nd 22.93 42.95 37.80 8.00 26.66 27.07 C22:6n-3 (DHA) 33.35 252.88 377.53 225.94 80.57 92.39 84.23 EPA+DHA 33.35 275.81 420.48 263.75 88.57 119.06 111.31 Total n-3 46.66 306.38 426.90 269.93 174.57 277.19 344.70 Thigh C18:3n-3 (ALA) 39.80 47.09 37.02 27.59 245.50 419.94 628.40 C20:5n-3 (EPA) 1.21 23.63 46.00 25.46 2.70 9.21 24.81 C22:6n-3 (DHA) 18.01 141.42 293.92 143.15 45.08 50.51 53.90 EPA+DHA 19.23 165.05 339.92 168.61 47.78 59.72 78.70 Total n-3 59.87 212.35 376.94 198.83 294.58 491.74 714.53 1Treatments consisted of 6% rice bran oil (RBO; Control), 2% tuna oil (TO) + 4% RBO (TO2), 4% TO + 2% RBO (TO4), 6% TO (TO6), 2% linseed oil (LO) + 4% RBO (LO2), 4% LO + 2% RBO (LO4), and 6% LO (LO6). nd: Not detectable. View Large CONCLUSIONS AND APPLICATIONS The main findings of the study are summarized below. Adding 6% tuna oil to the diet of slow-growing chickens reduced the final BW and increased the FCR. The breast meat of chickens fed with 6% linseed oil showed the highest boiling loss. Diets rich in n-3 PUFA oils did not significantly affect the meat cholesterol content. Feeding with 4% tuna oil boosted the DHA amounts (>250 mg/100 g fresh meat) in both breast and thigh meats. Supplementing the chicken diet with TO or LO (≥2%) enriched the PUFA content of the breast meat, achieving the “high in n-3 PUFA” requirement of the EU’s food market. Thigh meat supplemented with at least 2% TO or 6% LO reached the thresholds of 80 mg EPA+DHA/100 g meat and 600 mg ALA/100 g meat, respectively; thus, they qualify as “high in n-3 PUFA” in the EU’s food market. Footnotes Primary Audience: Nutritionists, Researchers, and Producers REFERENCES AND NOTES 1. Stark K. D. , Van Elswyk M. E. , Higgins M. 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Google Scholar PubMed 59. Betti M. , Perez T. I. , Zuidhof M. J. , Renema R. A. . 2009 . Omega-3-enriched broiler meat: 3. Fatty acid distribution between triacylglycerol and phospholipid classes . Poult. Sci. 88 : 1740 – 1754 . Google Scholar CrossRef Search ADS PubMed Acknowledgments We gratefully acknowledge the mainly support of the Thailand Research Fund (TRF) and the Suranaree University of Technology (SUT) under the project “Establishment of ‘Korat Meat Chicken’ Strain for Small and Micro Community Enterprise Production.” We also highly appreciate the “PhD Scholarship for Asean Countries” program of SUT for partly supporting this research. © 2017 Poultry Science Association Inc. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Journal of Applied Poultry ResearchOxford University Press

Published: Sep 1, 2018

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