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The effects of high-oleic peanuts as an alternate feed ingredient on performance, ileal digestibility, apparent metabolizable energy, and histology of the small intestine in laying hens †, ‡ † ‡ ‡ Adam K. Redhead, Elliot Sanders, Thien C. Vu, Ramon D. Malheiros, Kenneth E. Anderson, and †,1 Ondulla T. Toomer U.S. Department of Agriculture, Agricultural Research Service, Food Science and Market Quality and Handling Research Unit, Raleigh, NC 27695, USA; and Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC 27695, USA ABSTRACT: We aimed to determine the effects week 8 for histomorphometric analysis. Analysis of feeding a high-oleic peanut (HOPN) diet to of variance was performed on all variables using egg-producing laying hens on egg quality, digest- a general linear mixed model. Laying hens fed ibility, and feed conversion. Three isonitrogenous the CON-OA diet produced greater number of and isocaloric dietary treatments were formulated eggs relative to those fed the HOPN and con- with 1) Control diet (CON)—a corn-soybean meal trol diets (P < 0.05). The roche yolk color value conventional diet with 7.8 % added poultry fat, was higher (P < 0.001) in eggs from hens fed the 2) HOPN diet—dietary inclusion of ~20% coarse- HOPN diet. There were no differences in laying ground whole HOPN, and 3) oleic acid (CON-OA) hen performance, eggshell color, eggshell strength, diet—a control diet supplemented with 2.6% eggshell elasticity and egg albumen height, or egg oleic fatty acid oil. Ninety-nine 57-wk-old brown HU, ileal fat digestibility, or villi surface among Leghorn laying hens were randomly assigned to treatment groups. However, the apparent metab- 33 animals per treatment. Animals were housed olizable energy (P < 0.01) and ileal protein di- individually for 8 wk. Body and feed weights were gestibility (P = 0.02) were greater in laying hens recorded weekly and feed conversation ratio was fed the HOPN diet relative to the CON diet. This calculated. Bi-weekly, shell eggs were analyzed for study suggests that whole unblanched high-oleic quality (yolk color, albumen height, and Haugh peanuts may be an acceptable alternative feed in- unit [HU]). Jejunum samples were collected at gredient for laying hens. Key words: laying hens, alternative feed ingredients, high-oleic peanuts, feed ingredients, feed digestibility Published by Oxford University Press on behalf of the American Society of Animal Science 2021. This work is written by (a) US Government employee(s) and is in the public domain in the US. Transl. Anim. Sci. 2021.5:1-11 doi: 10.1093/tas/txab015 ingredients. Yet, over the last decade, animal feed INTRODUCTION ingredients have become more expensive with in- The poultry industry is one of the fastest creased demand for biofuel, as well as crop short- growing sectors in the world and has met the ages in different regions of the world (Seppelt growing global demand for food in the form et al., 2014). The poultry industries are of great of animal protein utilizing high-quality feed economic importance and represent a signifi- cant portion of the agricultural products sold in the southeastern United States (APHIS–USDA, Corresponding author: firstname.lastname@example.org 2015). However, the need for poultry feed ingre- Received September 8, 2020. Accepted February 2, 2021. dients such as corn and soybean meal far exceed 1 Redhead et al. the ability to produce these ingredients within However, no studies to date have examined the use this region. Hence, large quantities of grains and of whole high-oleic peanut cultivars (80% oleic high-protein oilseeds are imported from South acid and 2% linoleic acid) as a feed ingredient to America and the U.S. Midwest (ERS–USDA, 2017) improve digestibility and feed conversion in laying for animal feed and food production. hens. Thus, we aim to determine the effects of feed- Shapira et al. (2008) demonstrated that an ex- ing a 20% high-oleic peanut diet to egg-producing truded linseed-supplemented diet fed to laying hens laying hens on egg quality, ileal digestibility, and increased the omega-3 polyunsaturated fatty acid feed conversion of laying hens. content in table eggs compared with conventional eggs. Moreover, laying hens fed diets with varying MATERIALS AND METHODS levels of fish meal (0% to 20%) had increased doco- The procedures used in these studies were ap- sahexaenoic acid in egg yolk relative to increased proved by the North Carolina State University dietary inclusion of fish meal in comparison to the Institutional Animal Care and Use Committee controls with the exception of 15% and 10% fish (IACUC #19–761). meal (Howe et al., 2002). Nonetheless, although other laying hen feeding trials utilizing oilseed sup- plemented diets (sesame meal, sunflower meal) re- Experimental Design, Animal Husbandry, and ported no adverse effects on growth performance Dietary Treatments or egg quality, the lipid profile of the eggs produced from these feeding treatments was not different Three experimental diets were formulated to from conventional eggs (Mamputu and Buhr, 1995; be isonitrogenous (18% crude protein) and iso- Laudadio et al., 2014). caloric (3,080 kcal/kg) with an estimated particle Over the last two decades, agricultural and size between 800 and 1,000 µm (Table 1). The scientific research interests have focused on the diets were prepared 1 wk prior to the onset of whole peanut and peanut skins as an alternative the study and maintained at the feed mill (North feed ingredient for poultry (Toomer et al., 2019). Carolina State University) in a cool dry location. The poultry industries (broilers, eggs, turkeys) pre- A basal control diet (CON, treatment 1) was for- dominate within the U.S. southeast with Georgia mulated using yellow corn, conventional defatted being the top U.S. producer (National Agricultural soybean meal, corn gluten meal, wheat bran, Statistics Service, USDA, 2020). However, within limestone, and poultry fat as the six major feed this region, the need for poultry feed components ingredients containing 10% total fat. A whole such as corn and soybean meal exceed the ability to unblanched high-oleic peanut (HOPN) experi- produce these ingredients locally. Therefore, these mental diet (treatment 2) was formulated utilizing grains are imported from South America (Crop peanuts to replace conventional defatted soybean Prophet, 2019) and U.S. Midwest (Agweek, 2009). meal (dietary protein source) and poultry fat High-oleic and normal-oleic peanuts are grown (dietary lipids) feed ingredients in the basal con- abundantly within the U.S. Southeast with Georgia trol diet with 12.7% total fat in the finished feed, being the #1 U.S. producer. Hence, the use of high- while keeping the remaining four major feed in- oleic peanuts, as a protein and energy-rich feed in- gredient components the same as the basal con- gredient for poultry, utilizes regionally abundant trol diet (yellow corn, corn gluten meal, wheat commodities, such as peanuts to support animal bran, and limestone). As a consequence of limit- production within the U.S. Southeast, without the ing amino acid lysine, threonine, and methionine associated cost of importation of much needed in peanuts, it was necessary to supplement the corn and soybean meal feed stock rations. high-oleic peanut experimental diet with l -lysine, Previous feeding trials defined peanut meal l -tryptophan, and l -threonine (combined total made from normal-oleic peanuts (52% oleic acid <1%) to meet the amino acid requirements for and 27% linoleic acid) as a suitable laying hen feed egg-producing hens (NRC, 1994). A third experi- ingredient at 21%, 28%, and 35% inclusion of the mental diet (treatment 3) was formulated using diet (Pesti et al., 2003), and 35% inclusion of broiler oleic fatty acid oil to replace 98% of the poultry diets (Costa et al., 2001). Toomer et al. (2019) dem- fat feed ingredient in the basal control diet, while onstrated that eggs produced from laying hens maintaining similar levels of the five major feed fed an unblanched high-oleic peanut (20%) and ingredients found in the basal diet (yellow corn, corn diet had greater yolk color scores, oleic fatty conventional defatted soybean meal, corn gluten acid, and β-carotene levels relative to the controls. meal, wheat bran, and limestone). The oleic acid Translate basic science to industry innovation Performance of laying hens fed a peanut diet Table 1. Formulated Dietary Treatments and were collected, enumerated, and weighed daily Composition of Experimental Diets in Percent by and recorded from each hen. Bi-weekly, shell eggs Weight were analyzed for quality and USDA grading in the Egg Quality Lab (North Carolina State 1 2 3 Ingredient, % CON HOPN CON-OA University). Corn yellow 46.44 39.00 52.25 Soybean meal 21.44 0.00 20.45 Laying Hen Feed Analysis High oleic peanut, raw 0.00 20.00 0.00 Corn gluten 5.00 10.45 4.95 Total nitrogen was determined in homogenized Wheat bran 6.00 16.75 6.00 samples by combustion using an Elementar N cube Limestone 10.81 10.75 11.27 Poultry fat 7.80 0.00 0.05 analyzer (Elementar Americas, Mt. Laurel, PA) Oleic acid oil 0.00 0.00 2.60 according to the method 990.03 (AOAC, 2006). Di-calcium phosphorous 1.58 1.41 1.51 A Kjeldahl conversion factor of 6.25 (mixed food) Salt, plain 0.25 0.25 0.25 was used to calculate total protein in the samples. dl -Methionine 0.11 0.08 0.10 Total fat as triglycerides was determined in the l -Lysine 0.00 0.49 0.00 samples gravimetrically after Soxhlet extraction. l -Tryptophan 0.00 0.06 0.00 Samples were extracted for 6 h using continuous l -Threonine 0.00 0.12 0.01 extraction with hexane (Method 920.39; AOAC, Propionic acid 0.05 0.05 0.05 1990). Choline chloride 0.17 0.24 0.16 Trace mineral mix 0.20 0.20 0.20 Egg Quality and Grading Vitamin mix 0.10 0.10 0.10 Selenium 0.05 0.05 0.05 Albumen height was measured and Haugh unit CON = conventional corn and soybean diet. (HU; Haugh, 1937) was calculated and recorded HOPN = high-oleic peanut + corn. using the TSS QCD system (Technical Services and CON-OA = control spiked with 2.6% oleic fatty acid oil. Supplies, Dunnington, York, UK) to determine NC State University mineral premix supplied the following per kg egg albumen quality. Yolk color was determined of diet: manganese, 120 mg manganese, 120 mg zinc, 80 mg iron, 10 mg copper, 2.5 mg iodine, and 1 mg cobalt. by using TSS QCD System yolk color scan, which NC State University vitamin premix supplied the following per kg was calibrated to the DSM Yolk Color Fan (a color of diet: 13,200 IU vitamin A, 4,000 IU vitamin D3, 33 IU vitamin E, index 1 to 15 to distinguish the yolk color density 0.02 mg vitamin B , 0.13 mg biotin, 2 mg menadione (K3), 2 mg thia- from lightest to darkest color intensity; Vuilleumier, mine, 6.6 mg riboflavin, 11 mg d -pantothenic acid, 4 mg vitamin B , 55 mg niacin, and 1.1 mg folic acid. 1969). Eggs were evaluated for exterior and interior NC State University selenium premix provided 0.2 mg Se (as grade standards in accordance with the USDA Na SeO ) per kg of diet. 2 3 Standards (USDA, 2010). Eggs were sized weekly by treatment (USDA, 2010). Egg sizing was classified by a minimum net weight per egg: peewee (<42.6 g), (CON-OA) used was food grade quality pur- small (42.6 < 49.7 g), medium (49.7 < 56.8 g), large chased from Millipore Sigma (Burlington, MA) (56.8 < 63.9 g), extra-large (63.9 < 70.9 g), and with the finished feed containing 6.2% total fat. jumbo (>70.9 g). Eggshell strength was tested using Experimental finished diets were analyzed and a TA-HD plus texture analyzer and elasticity for all determined to be free of aflatoxin and micro- treatment groups (Texture Technologies Corp. and biological contaminants by the North Carolina Stable Micro Systems Ltd., Hamilton, MA). Department of Agriculture and Consumer Services, Food and Drug Protection Division Laboratory (Raleigh, NC). Lipid and Fatty Acid Analysis Ninety-nine 57-wk brown leghorn laying hens (North Carolina State University Flock) were Lipid and fatty acid analysis (total fat, total randomly assigned to one of three treatment cholesterol, total palmitic acid, total stearic acid, groups. Each treatment was replicated three times total oleic fatty acid, n9 elaidic acid, total lino- with 11 laying hens per replicate with 33 laying lenic acid, and total linoleic fatty acid) of feed hens and one laying hen per replicate cage at the samples from the three treatment groups (Table 2) Chicken Educational Unit (North Carolina State were analyzed using modified direct methylation University). Laying hens were provided feed and methods as described by Wang et al. (2000) in the water ad libitum throughout the 8-wk study. Body Food Science and Market Quality and Handling and feed weights were recorded weekly. Shell eggs Research Unit. Translate basic science to industry innovation Redhead et al. Table 2. Chemical Lipid and Fatty Acid Analysis of Dietary Treatments 2 3 4 Chemical component CON HOPN CON-OA SEM P-value Percentage of total lipid content, % b a c Crude fat 10.06 12.71 6.18 0.037 <0.001 a c b Palmitic acid (16:0) 22.58 7.51 14.64 0.005 <0.001 a c b Palmitoleic acid (16:1cis) 5.46 0.510 1.27 0.001 <0.001 c a b Oleic acid (18:1) 38.42 74.19 43.8 0.003 <0.001 b c a Elaidic acid (trans-9 C18:1) 2.78 0.94 5.84 0.012 <0.001 a c b Linoleic acid (18:2) 21.69 8.77 20.67 0.001 <0.001 b c a Linolenic acid (18:3cis) 1.04 0.42 1.66 0.001 <0.001 a c b Stearic acid (18:0) 5.37 1.92 3.81 0.002 <0.001 a b c Omega 6 21.69 8.77 1.28 0.001 <0.001 a b c Total cholesterol 50.40 8.40 3.59 0.007 <0.001 b a c Gross energy, kcal/kg feed 4,129 4,205 3,802 0.045 <0.001 Three replicate samples were collected from each dietary treatment and were analyzed for lipid and fatty acid content. Fatty acid content defined as the percentage of the total lipid content of 100-g sample. CON = conventional corn and soybean diet. HOPN= high-oleic peanut + corn. CON-OA = control spiked with 2.6% oleic fatty acid oil. a,b Means within the same row lacking a common superscript differ significantly (P < 0.05). Ileal Digestibility, Metabolize Energy, and diverticulum to the ileal–cecal–colon junction, the Intestinal Morphology Analysis digesta contents were gently squeezed (using fin- gers and small amounts of distilled water from a To determine the digestibility of the feed ingre- wash bottle) directly into 250-mL specimen cups. dients, the feed that was fed to the birds during the Ileum digesta samples were held on ice and then last 5 d contained 2% of CELITE (Diatomaceous frozen (−15 °C) and stored for future analysis. Earth; Celite Corp, Lompoc, CA) as an insoluble Excreta from each hen was collected for 48 hr in ash marker in the diet. This was done to evaluate aluminum pans directly placed under each cage the digestibility of nutrients with a partial excreta and hen 2 d prior to termination of the experiment. collection, according to Huang et al. (2006). Subsequently, the excreta from each cage was keep At termination of the experimental period, nine in separate plastic bags and stored at −18 °C, until laying hens per treatment (three per replicate) were further analyzes. selected for sampling of the jejunum, ileum content, Excreta, ileal contents, and feed samples were and excreta. Samples of the jejunum were collected for oven dried at 70 °C for 48 h and ground through histomorphometric analysis using standard light histo- a 1-mm screen prior to analysis. Gross energy logical H&E staining procedures. Briefly, a 1-cm seg- (GE) of feed and dried digesta was determined by ment of the midpoint of the duodenum and the distal adiabatic oxygen bomb calorimeter (IKA model end of the lower ileum were removed and fixed in 10% C5003 connected to compressed oxygen with buffered formalin for 72 h. Each segment was then em- NESLAB Refrigerated Re-circulator CFT-25). bedded in paraffin, and a 2-μ m section of each sample Digesta and feed samples were placed in a pellet was placed on a glass slide and stained with hema- press and compacted. Compacted samples were toxylin and eosin for examination with a light micro- weighed and recorded. Samples were placed into scope (Sakamoto et al., 2000). Jejunal villus height was a metal thimble and IKA brand 50J cotton twist measured from the villus tip to the villus crypt junction for combustion in the decomposition vessel or and crypt depth was identified as the depth between combustion canister. Samples were placed within two adjacent villi, according the methodology of Solis the decomposition vessel, sealed, and the cali- de los Santos et al. (2005). The parameters evaluated brated samples were combusted. Acid-insoluble were villus height, villus base, villus surface area, lamina ash determination of feed and excreta samples propria thickness, and crypt depth. Morphological were determined using ash residue (Vogtmann parameters were measured using the Image Pro Plus v et al., 1975). Samples were boiled in 25 mL of 4.5 (Media Cybernetics, Rockville, MD). 4N hydrochloric acid, washed, and filtered using To collect the ileum contents after separ- ash-less paper. Subsequently, the filter paper and ation of the whole intestine tract, from Meckel’s residue were placed in a muffle furnace at 600 °C Translate basic science to industry innovation Performance of laying hens fed a peanut diet for 10 h, cooled, and weighed. Digesta collected RESULTS from the ileum and feed samples were dried over a 2-d period in an industrial Blue-M Drying oven Feed Analysis at 70 °C. Dried samples were finely ground. Total The experimental diets were formulated to be fat content was determined gravimetrically after isocaloric (18% crude protein) and isonitrogenous Soxhlet extraction. Samples were filtered and (3080 kcal/kg feed); however, upon analysis, the placed within Whatman Cellulose extraction fatty acid profiles for the diets were different. The thimbles (26 mm × 60 mm) and loaded within the analyzed crude protein content of the experimental Soxhtec System HT 6 1043 extraction unit Foss diets was the following: CON 16.84% crude protein, Tecator. Clean and labeled 100-mL metal canisters HOPN diet 17.68% crude protein, and CON-OA were weighed by the same scale and then filled with diet 19.18% crude protein (data not shown). Upon 50 mL of diethyl ether. Weights of the samples and chemical analyzation, the HOPN diet had greater the canisters were recorded. The metal canisters (P < 0.001) crude total fat relative to the CON were placed into metal loaders and sealed within and CON-OA diets (Table 2). The CON diet had the extraction unit underneath the cellulose thim- a greater content (P < 0.001) of saturated fatty bles and heated to 60 °C. Loaded samples were acids, palmitic acid, and stearic acid, relative to allowed to remain in diethyl ether for 40 min at the HOPN and CON-OA diets. Additionally, the 60 °C. Extracted fat present within the metal can- CON-OA diet was greater in both palmitic acid ister was weighed and recorded to determine ratio (P < 0.001) and steric acid (P < 0.001) compared of fat of each sample. Additionally, feed, ileum, with the HOPN diet. and fecal samples were shipped to ATC Scientific The HOPN diet had a greater (P < 0.001) (Little Rock, AR) for proximate analysis of crude amount of the monounsaturated oleic fatty protein. Total nitrogen levels were determined acid relative to the control diet. In addition, the through combustion using an Elementar N cube CON-OA had a greater (P < 0.001) content of OA analyzer (Elementar Americas, Mt. Laurel, PA) relative to the control diet. However, the monoun- on homogenized samples according to method saturated fatty acid palmitoleic acid was greater 990.03 (AOAC, 2006) methods. The total protein (P < 0.001) in the control diet compared with in each sample was calculated using a Kjeldahl the HOPN and CON-OA diets. Additionally, the conversion factor of 6.25. Apparent metaboliz- CON-OA diet had a greater (P < 0.001) palmitoleic able energy, corrected by nitrogen calculated, was acid content compared with the HOPN diet. The calculated using the following formula (Titus, CON-OA diet had a greater (P < 0.001) amount 1956; Li et al., 2013): of trans-fatty acid elaidic acid compared with the HOPN and control diets. Yet, the CON diet had GE (feed) − [GE (fecal) a greater (P < 0.001) amount of elaidic acid com- × (acid insoluble ash recovery feed)/ pared with the HOPN diet. (acid insoluble ash recovery fecal) − 8.22 The control and CON-OA experimental diets × (crude protein fecal/6.25)] had greater (P < 0.001) amounts of the polyunsat- urated fatty acid linoleic acid in comparison to the control diet. Additionally, the CON-OA diet had Statistical Analysis a greater (P < 0.001) linoleic acid (18:2) content Individual dependent variables (with each compared with the HOPN diet. Also, the CON and cage per hen serving as an experimental unit) CON-OA diets had greater (P < 0.001) amount of were analyzed as a one-way analysis of variance the linolenic acid (18:3) relative to the HOPN diet. (ANOVA) using the Proc Mixed procedure of The CON diet had greater (P < 0.001) omega 6 and JMP (2013) using a general linear mixed model total cholesterol levels in comparison to the HOPN to evaluate differences between the control and and CON-OA diets. However, the HOPN diet had treatments. Means were separated at P < 0.05 a greater (P < 0.001) amount of omega 6 and chol- using least squares means with Tukey–Kramer esterol relative to the CON-OA diet. Lastly, the adjustment for multiple comparisons. Data are HOPN diet had more (P < 0.001) gross energy in expressed as means and SEM. Means were con- comparison to the CON and CON-OA diets, while sidered significantly different among treatments the CON diet had more (P < 0.001) gross energy when P < 0.05. relative to the CON-OA diet (Figure 1). Translate basic science to industry innovation Redhead et al. Figure 1. Effect of a high-oleic peanut diet on apparent protein ileal digestibility and metabolizable energy in laying hens. Three isonitrogenous experimental diets (approximately 18% crude protein) were fed to ninety-nine 57-wk-old laying hens with 33 laying hens per treatment with three replicates of 11 laying hens per replicate for 8 wk: Conventional corn and soybean diet (CON), high-oleic peanut + corn (HOPN), or control spiked a,b with 2.6% oleic fatty acid oil (CON-OA). Each bar graph represents the average ± SEM. Bar graphs with differing superscript are significantly different (P < 0.05). Egg Production Parameters Table 3. Laying hen egg production parameters and quality of eggs produced by hens fed diets Laying hens fed the CON-OA diet had higher containing high-oleic peanuts (HO PN), oleic acid number of eggs/hens at time points week 2 (P = 0.005) (OA), or a conventional soybean meal and week 6 (P = 0.03) as compared with hens fed HO Item Dietary treatment PN diet (Table 3). Yet, there were no treatment differ- 1 2 3 4 CON HOPN CON-OA SEM P-value ences in the total number of eggs produced between Number of eggs/hen treatments groups at week 4 and week 8. Also, there ab b a Week 2 12.9 12.5 13.6 0.22 0.005 were no differences in egg weight between experi- Week 4 12.6 12.4 13.1 0.30 0.18 mental groups at weeks 4 and 8, while there were dif- ab b a Week 6 19.1 18.6 20.0 0.40 0.03 ferences at week 2 (P = 0.005) and week 6 (P = 0.005) Week 8 10.72 10.12 10.6 0.40 0.5 in egg weights, with smaller egg weights produced Egg weight, g from hens fed the HOPN diet relative to the CON a b ab Week 2 67.25 62.36 64.65 1.02 0.005 diets. There were no differences (P < 0.05) in the egg Week 4 66.59 65.57 66.26 1.20 0.82 a b ab HU between the treatment groups at any of the time Week 6 66.56 62.01 65.25 0.97 0.005 points measured (weeks 2, 4 6, and 8). Laying hens Week 8 68.02 65.70 64.87 1.22 0.18 Haugh unit, HU fed the CON diet had a higher feed conversion ratio Week 2 90.05 92.50 92.72 2.26 0.65 (FCR; kg feed/dozen eggs) at week 2 (P = 0.01) and Week 4 95.16 94.14 92.85 1.56 0.58 week 4 (P = 0.0002) relative to the CON-OA and Week 6 89.74 94.93 94.85 1.80 0.07 HOPN diets, whereas there were no differences in Week 8 91.52 91.31 91.13 1.64 0.99 FCR between treatments at week 6 and week 8. There FCR, kg feed/dozen eggs were no significant differences between treatment a ab b Week 2 3.46 2.98 2.63 0.20 0.01 blocks and replicates within each treatment. a b b Week 4 2.28 1.79 1.72 0.10 < 0.001 Week 6 1.91 1.81 1.80 0.09 0.68 Egg Quality Week 8 2.01 2.13 2.22 0.16 0.63 All eggs produced at all-time points (week 1 to CON = conventiosnal corn and soybean diet. HOPN = high-oleic peanut + corn. week 8) between the experimental treatments were CON-OA = control spiked with 2.6% oleic fatty acid oil. graded as USDA Grade AA of superior quality. SEM = standard error of mean. The shells were clean, without defects and there Number of eggs/hen at 2-wk intervals. were minimal number of blood spots or meats FCR = feed conversion ratio at 2-wk intervals, kg total feed con- pots. The yolk color roche score was examined sumed/total dozen eggs produced. bi-weekly to determine the yolk color intensity a,b Means within the same row lacking a common superscript differ produced from the dietary treatments (Table 4). significantly (P < 0.05). Translate basic science to industry innovation Performance of laying hens fed a peanut diet Table 4. Egg quality of eggs produced from laying were no differences in shell color, shell strength, hens fed a diet with high-oleic peanuts (HO PN), shell elasticity, and albumen height between the oleic acid (OA), or a conventional diet with soy- treatment groups at any of the time points meas- bean meal ured (weeks 2, 4, 6, and 8). There were no sig- nificant differences between treatment blocks and Item Dietary treatment replicates within each treatment. 1 2 3 4 CON HOPN CON-OA SEM P-value Yolk color (1 to 15) Apparent Ileal Digestibility, Apparent b a b Week 2 5.28 6.17 5.17 1.64 <0.0001 Metabolizable Energy, and Intestinal Morphology b a b Week 4 4.67 7.44 5.22 0.19 <0.0001 c a b Week 6 5.00 6.83 5.94 0.20 <0.0001 There were no differences in apparent ileal fat b a b Week 8 4.78 6.22 5.33 0.22 <0.0001 digestibility (P = 0.14; CON 95.7 ± 5.5 vs. HOPN Shell color 80.4 ± 5.5 vs. CON-OA 92.6 ± 5.5 %) or villi sur- Week 2 26.89 29.02 25.89 1.41 0.28 face area (P = 0.58; CON 2,6797.9 ± 5,359 vs. Week 4 26.95 27.88 24.82 1.17 0.17 Week 6 23.41 24.44 24.55 1.02 0.68 HOPN 18,594.6 ± 5,620 vs. CON-OA 22,547.4 ± Week 8 27.14 26.01 24.38 1.08 0.20 22,547 µm ) between treatment groups after 8 wk Shell strength, g of feeding the experimental diets in laying hens. Week 2 5,147.5 4597.5 4738.0 179.2 0.08 However, the corrected apparent metabolizable en- Week 4 4,890.8 5406.8 5240.4 208.3 0.21 ergy (P < 0.001; Figure 1) was greater in laying hens Week 6 4,969.3 5366.3 5048.0 158.5 0.18 fed the HOPN diet compared with hens fed the Week 8 4,305.1 4712.6 4629.5 190.8 0.28 CON and CON-OA diets. Ileal protein digestibility Shell elasticity, mm was greater in hens fed the HOPN diet relative to Week 2 0.286 0.229 0.243 0.006 0.17 the controls (P = 0.02; Figure 1), whereas the ileal Week 4 0.231 0.234 0.243 0.007 0.44 protein digestibility was similar between hens fed Week 6 0.240 0.250 0.240 0.008 0.57 the control and CON-OA diets. There were no sig- Week 8 0.215 0.233 0.227 0.006 0.16 nificant differences between treatment blocks and Albumen height, mm Week 2 8.77 8.80 8.89 0.35 0.96 replicates within each treatment. Week 4 9.63 9.2 8.98 0.37 0.45 Week 6 8.59 9.20 9.35 0.32 0.22 DISCUSSION Week 8 8.84 8.73 8.64 0.31 0.90 Although the experimental dietary treatments CON = conventional corn and soybean diet. were formulated to be isocaloric and isonitrog- HOPN = high-oleic peanut + corn. enous, the HOPN diet had a greater amount of CON-OA = control spiked with 2.6% oleic fatty acid oil. crude fat and gross energy relative to the CON and SEM = standard error of mean. CON-OA diets. Dietary energy is acquired from Yolk color was determined using the Roche Color Fan color index dietary carbohydrates and lipids, found in the yellow 1 to 15 to distinguish lightest to darkest, respectively. corn and poultry fat feed ingredients in the CON Shell color is based on the reflectance with the lower the number the whiter the shell. diet. Oleic fatty acid oil replaced 98% of the poultry Egg albumen height (mm was calculated to determine egg albumen fat in the CON diet formulation, thus yellow corn, quality). and oleic fatty acid along with minor amounts of a,b Means within the same row lacking a common superscript differ poultry fat were sources of dietary energy in the significantly (P < 0.05). CON-OA feed treatment. High-oleic peanuts are rich in (≈50%) lipids and (≈30%) proteins (Settaluri Interestingly, the yolk color roche value was et al., 2012; Zhao et al., 2012), thus formulation greater (P < 0.001) in eggs produced from laying with HOPN served to replace two of the six major hens fed the HOPN diets relative to the other feed ingredient components of the basal control treatment at all-time points measured. At weeks diet (soybean meal and poultry fat) and provided 2, 4, and 8, there were no differences in egg yolk both dietary energy and protein in combination. color intensity between laying hens fed the CON Additionally, the HOPN feeding treatment was for- and CON-OA diets. At week 6, egg yolk color mulated with yellow corn, providing a major source intensity was different between all treatment of dietary energy, which explains increased levels of groups, with eggs produced from hens fed the total gross energy relative to the other experimental HOPN diet having the greatest yolk color inten- diets and increased apparent metabolizable energy. sity, and eggs produced from hens fed the CON In general peanuts (normal oleic and high oleic) and diet having the lowest yolk color intensity. There Translate basic science to industry innovation Redhead et al. peanut oil contain three major fatty acids that are eggs with lower weights relative to conventional present as acylglycerols esters formed from glycerol eggs. Thus, it could be assumed that feeding a diet and fatty acids palmitic, oleic acid, and trace levels rich in unsaturated fatty acids in laying hens as a of linoleic acid (Carrin and Carelli, 2010). Studies potential feeding regimen to reduce oversized eggs have shown that linoleic essential fatty acid defi- produced in older laying hens. ciencies in the diets of laying hens adversely affect In this study, there were no differences in the egg egg production, whereas dietary fats are required HU, between laying hens fed the control, HOPN and for the absorption of fat-soluble vitamins (A, D, CON-OA diets across all experimental time points E, and K) needed for egg production (Jacob et al., (weeks 2, 4, 6, and 8). In parallel, Krawczyk et al. 1998). Thus, the poultry fat (control diet), high- (2015) evaluated the effects of various dietary in- oleic peanuts (HOPN diet), and oleic fatty acid oil clusion levels of raw yellow lupine seed meal on egg (CON-OA diet) in the experimental diets provided quality and reported that no differences were found the dietary fats needed for absorption of fat-soluble between the conventional controls and experimental vitamins, while providing ample dietary linoleic es- treatment groups. Also, Toomer et al. (2019) reported sential fatty acid for egg production. that no differences in egg quality were found between Laying hens fed the CON-OA diet produced a laying hens feed a HOPN supplemented diet and greater number of eggs relative to the number of CON diet after 10 weeks. But other studies by Yuan eggs produced by hens fed the HOPN diet, with et al. (2019) demonstrated that dietary supplementa- exception of the last week of the study. However, tion with rapeseed oil to egg-producing hens improved there were no differences in the total number of eggs albumen quality in the eggs produced. produced upon comparison between the CON-OA The yolk color (DSM Yolk Color Fan) score and CON and upon comparison of the HOPN and was examined bi-weekly to determine the yolk CON, suggesting that egg production is not influ- color intensity of eggs produced from the three enced by source of dietary lipids (98% oleic fatty experimental diets. Yolk color was greater in eggs acid + 2% poultry fat in CON-OA diet vs. 100% produced from hens fed the HOPN diets at all-time poultry fat in CON diet). Also, these results suggest points when compared with eggs produced from that egg production is not influence by the source hens fed the CON-OA and CON. Similarly, Toomer of dietary protein/amino acids upon comparison of et al. (2019) reported that eggs produced from egg production between HOPN fed hens and CON laying hens fed a HOPN diet had greater yolk color fed hens (high-oleic peanuts providing a combined scores relative to hens fed a conventional soybean source of protein and lipids in the HOPN diet meal and corn control diet. Although Sangkaew versus soybean meal providing primary source of et al. (2019) demonstrated no significant differences protein in the control diet). Research has shown in yolk color scores between eggs produced from that laying hen egg production is adversely affected layers fed a conventional diet versus a diet of high- by inadequate dietary energy, protein, or calcium oleic sunflower oil (HOSO) diet, yolk color scores and requires a nutritionally balanced diet for op- were observably darker in eggs produced from hens timal egg production (Jacob et al., 1998). fed the HOSO diet relative to the controls. Within the first 4 wk of the study, hens fed the Yolk color depends on the consumption of pig- CON-OA diet had an improved FCR compared mented substances (i.e., carotenoids) found in the with hens fed the CON diet. Additionally, hens feed (Lessire et al., 2017). Sangkaew et al. (2019) fed the HOPN experimental diet had improved suggested that the color intensity increase may be FCR in comparison to hens fed the conventional due to the high level of pigment (β-carotene) in control diet at the 4-week time point. Hence, sug- the diets in which sunflower oil contains the nat- gesting that HOPN fed birds consumed less of the ural pigment β-carotene similar to that found in energetically dense HOPN experimental diet to the unblanched high-oleic peanut diet and peanut meet the metabolic needs of similar bi-weekly egg oil. A possible explanation for the increase in production comparative to the other treatment yolk color intensity may be due to the carotenoid groups while utilizing less total feed (kilogram) and and/or polyphenolic compounds found present improved FCR. in unblanched high-oleic peanuts (Toomer et al., At weeks 2 and 6, eggs produced from hens fed 2019) in addition to the source and level of natural the HOPN diet had reduced egg weights relative pigments precursors in the diet (An et al., 2010). In to the CON, which parallel results by Van Elswyk this study, the HOPN diet contained slightly higher et al. (1994) demonstrating that hens fed a diet rich corn gluten meal, which may have contributed to a in unsaturated fatty acids from fish oil produced minor influence on yolk color intensity. Jiang et al. Translate basic science to industry innovation Performance of laying hens fed a peanut diet (2013) and Swiatkiewicz and Koreleski (2006) dem- to the presence of a combination of various nutri- onstrated that increasing the concentration of corn ents found within grains and oilseeds. Protein ileal distillers dried grains with solubles (DDGS) fed to digestibility was enhanced in hens fed the HOPN laying hens increases the yellow color intensity in diet relative to CON fed hens, implying that protein the yolk. As the DDGS level increased in the diet within the high-oleic peanuts (predominate source xanthophyll pigment concentration also increases, of protein) and the minor amount of free amino resulting in the increase in yolk color intensity (Sun acids supplemented to the HOPN diet (<1% total) et al., 2013). In addition, the xanthophyll content in provided greater digestible protein relative to soy- DDGS is three times as concentrated due to the re- bean meal in the control diet. Although grains and moval of starch in the fermentation process during oilseeds may provide a primary source of nutrients preparation (Jiang et al., 2013). Abd El-Hack et al. (yellow corn-carbohydrates, peanuts-protein, soy- (2019) also demonstrated that increasing the con- bean meal-protein), they also provide other nutrients centrations of DDGS (0%, 6%, 12%, and 18%) in- in combination (carbohydrates, fiber, minerals, vita- creased yolk color density. However, eggs produced mins). Thus, we aim to perform future studies util- from laying hens fed diets supplemented with rape- izing purified experimental diets for improved dietary seed oil (Yuan et al., 2019) and/or canola oil at con- comparisons and interpretation of the dietary effects centrations 2%, 4%, and 6% (Gul et al., 2012) had between feed ingredients. reduced yolk color intensity scores relative eggs In summary, feeding a HOPN diet to laying hens produced by laying hens fed the control diet. increased egg yolk color, apparent metabolizable en- Eggshell quality, color, and strength can be af- ergy, and ileal protein digestibility relative to a conven- fected by many factors such as strain, age, and nu- tional soybean meal and corn laying hen diet. Thus, trition (Mu et al., 2019). In this study, there were no suggesting that whole unblanched high-oleic peanuts differences in shell color, shell strength, shell elasti- may be an acceptable protein and energy-rich feed in- city, and albumen height between dietary treatment gredient for laying hens. However, additional studies are groups at weeks 2, 4, 6, and 8. In parallel, other stud- needed to further explore the effects of a HOPN diet ies demonstrated that eggs produced from laying hens on the nutrient digestibility in laying hens and to deter- fed diets supplemented with various feed ingredients mine the true economic feasibility of whole unblanched such as myoinositol (Zyla et al., 2012), full fat soy- high-oleic peanuts as a poultry feed ingredient. beans at inclusion levels 10% to 22% (Senkoylu et al., 2005), glycerol (Cufadar et al., 2016), yellow lupine ACKNOWLEDGMENTS (Krawczyk et al., 2015), and hemp seed and hemp seed oil (Gakhar et al., 2012; Neijat et al. (2014) had The authors gratefully acknowledge the no effect on egg shell strength, eggshell weight, egg- Prestage Department of Poultry Science, the NC shell thickness, and albumen height. However, Jiang State University Feed Mill, Birdsong Peanuts, et al. (2013) and Shalash et al. (2010) reported that and the Food Science and Market Quality and including DDGS increased eggshell thickness while Handling Research Unit-ARS for their con- not affecting eggshell strength. tributions to this study. This work was sup- In this study, there were no differences in fat di- ported by funds from the North Carolina Peanut gestibility or villi surface area between dietary treat- Growers Association (Funding Source 572099- ment groups (data not shown). However, the apparent 87361) and the Food Science & Market Quality & metabolizable energy and ileal protein digestibility Handling Research Unit – ARS – United States were higher in laying hens fed the HOPN diet relative Department of Agriculture (CRIS Project Number to the CON diet, implying that the HOPN diet sup- 6070-43440-011-00D). plied a greater amount of digestible dietary energy Conflict of interest statement. The authors have relative to the other treatment groups. Dietary en- no conflicts of interest to declare. ergy is obtained from carbohydrate and lipid sources within the diet. Yellow corn and poultry fat were the primary sources of dietary energy in the conventional LITERATURE CITED control diet, whereas the lipids in the high-oleic pea- Abd El-Hack, M. E., K. M. Mahrose, F. A. M. Attia, nuts would have provided the primary source of A. A. Swelum, A. E. Taha, R. S. Shewita, and dietary energy in the HOPN diet. Nonetheless, the A. N. Alowaimer. 2019. 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Translational Animal Science – Oxford University Press
Published: Feb 4, 2021
Keywords: laying hens; alternative feed ingredients; high-oleic peanuts; feed ingredients; feed digestibility
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