Inclusion of dietary β-mannanase improves performance and ileal digestibility and reduces ileal digesta viscosity of broilers fed corn-soybean meal based diet

Inclusion of dietary β-mannanase improves performance and ileal digestibility and reduces ileal... ABSTRACT This study was aimed to evaluate the influence of dietary β-mannanase inclusion on growth performance, apparent ileal digestibility, digesta viscosity, blood metabolites and excreta noxious gas emissions in broilers fed corn-soybean meal based diet. A total of 600 conventional healthy 1-d-old ROSS 308 broilers with body weight 45 ± 0.50 g (mean ± SD) were randomly assigned to 4 dietary treatments with 10 replicates cages, with 15 broilers in each and fed basal diet supplemented to corn-SBM based diets with 0, 2400, 4800, and 7200 MNU β-mannanase/kg for 35 d feeding trial period. Significant results were observed on improved average daily gain and reduced feed conversion ratio during trial period and also reduced ileal digesta viscosity and improved apparent ileal digestibility of dry matter, nitrogen and energy. However, no significant effects were found on blood urea nitrogen and creatinine, excreta noxious gas emissions. In conclusion, the inclusion of dietary β-mannanase had potential to improve daily gain and feed efficiency and apparent ileal digestibility while decreasing digesta viscosity of broiler. INTRODUCTION Soybean meal (SBM) is a major protein source and one of the valued ingredients in poultry feeds. The corn-SBM based poultry diets account for 15–34% of total non-starch polysaccharides (NSP) contents of the diet and help to increase the viscosity of digesta, modify the physiology of the gastrointestinal tract and change the ecosystem in the gut (Jackson et al., 1999). Exogenous addition of enzymes was required as the digestive tract of poultry lack the enzymes targeting β-1,4-mannosyl; in turn limiting the nutrient and energy digestibility and growth performance (Jackson et al., 2004). Barros et al. (2015) observed that β- mannanase is responsible for the hydrolysis of β-mannans, thus reducing intestinal viscosity and promoting better nutrient digestibility. Beneficial effects of the inclusion of a β-mannanase in broilers fed diets containing SBM for the enzymatic degradation of β-mannan was reported (Daskiran et al., 2004). During the past few years, β-mannanase has been purified and characterised from various organisms collectively known as mannan degraders (Dhawan and Kaur, 2007). The present study was designed to determine effects of β-mannanase (from Trichoderma citrinoviride) in corn-SBM based diet on growth performances, ileal digesta viscosity, apparent ileal digestibility (AID), blood metabolites and excreta noxious gas emissions in broilers. MATERIALS AND METHODS The protocol for the experiments was approved and birds were maintained according to the guidelines of the Animal Care and Use Committee of Dankook University, Cheonan, South Korea. Source of β-mannanase The commercial exogenous enzyme, β-mannanase (DigeGrain M, Advanced Enzymes Technologies Ltd. Thane (W), India) was produced by controlled fermentation of Trichoderma citrinoviride and contained 24,000,000 β-mannanase units (MNU)/kg. One unit of β-mannanase is the amount of enzyme, which liberates 1 μmol of total reducing sugar (glucose equivalent) from mannan substrate (Locust bean gum) per minute at pH 5.3 and 50°C. This product is extremely effective in hydrolyzing mannan and is stable up to 85°C. Experimental Design, Birds and Husbandry A total of 600 conventional healthy 1-d old Ross 308 broiler chicks (mixed gender) having average BW of 45 ± 0.50 g (mean ± SD) were used in the experiment which lasted for 35 days. Chicks were randomly allotted into one of four treatment diets (10 replicate cages/treatment, 15 chickens/cage). Chickens were grown in a room of 33±1°C for the first 3 days and the temperature was reduced gradually until 24°C maintaining humidity around 60% for the rest of the experiment. Stainless steel cages (1.75 × 1.55 m) of identical size were managed for chickens housing and with free access to feed and water. Diets fed to chickens were: CON (basal diet), basal diet supplemented with 2400, 4800, and 7200 MNU β-mannanase/kg diet. The basal diets were formulated to meet or exceed the nutritional requirements of broilers during starter (d 0 to 18) and finisher (d 19 to 35) phases, according to NRC (1994) recommendations for broiler chickens (Table 1). Table 1. Ingredient composition of experimental diets (as-fed basis). Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  †Provided per kg of complete diet: 11,025 IU vitamin A; 1103 IU vitamin D3; 44 IU vitamin E; 4.4 mg vitamin K; 8.3 mg riboflavin; 50 mg niacin; 4 mg thiamine; 29 mg d-pantothenic; 166 mg choline; 33 μgvitamin B12. ‡Provided per kg of complete diet: 12 mg Cu (as CuSO4•5H2O); 85 mg Zn (as ZnSO4); 8 mg Mn (as MnO2); 0.28 mg I (as KI); 0.15 mgSe (as Na2SeO3•5H2O). §Ether extract represents total fat content in the diet. View Large Table 1. Ingredient composition of experimental diets (as-fed basis). Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  †Provided per kg of complete diet: 11,025 IU vitamin A; 1103 IU vitamin D3; 44 IU vitamin E; 4.4 mg vitamin K; 8.3 mg riboflavin; 50 mg niacin; 4 mg thiamine; 29 mg d-pantothenic; 166 mg choline; 33 μgvitamin B12. ‡Provided per kg of complete diet: 12 mg Cu (as CuSO4•5H2O); 85 mg Zn (as ZnSO4); 8 mg Mn (as MnO2); 0.28 mg I (as KI); 0.15 mgSe (as Na2SeO3•5H2O). §Ether extract represents total fat content in the diet. View Large Sampling and Measurements Feed samples were ground to pass through a 1-mm screen, after which they were analysed for dry matter (DM, method 934.01; AOAC, 2000), nitrogen (N, method 968.06; AOAC, 2000), ether extract (method 920.39; AOAC, 2000). Individual amino acid (AA) composition was measured using an AA analyser (Beckman 6300; Beckman Coulter Inc., Fullerton, CA) after a 24 h hydrolysis in HCl (Spackman et al. 1958). For the determination of Cys and Met, the samples were oxidised with performic acid overnight at 0°C (Moore, 1963). Nitrogen was determined using Kjectec 2300 Nitrogen Analyzer (Foss Tecator AB, Hoeganaes, Sweden), and crude protein was calculated as N × 6.25. Test ingredients were hydrolyzed with 72% (w/w) H2SO4 for 1 h, diluted with distilled water to final concentration of H2SO4 at 1 N and incubated at 121°C for 45 min to determine mannan content. Mannan contents in the hydrolysates were determined using an evaporative light scattering detector and a Shodex sugar column SP0810 (8.0 mm × 300 mm; Showa Denko K.K., Tokyo, Japan) according to the procedures described by Mok et al., (2013). Broilers were weighed, and feed intake was recorded at d 1, d 18, and d 35. Average daily gain (ADG), average daily feed intakes (ADFI), and feed conversion ratio (FCR, pen basis) were determined for each phase. From d 29 to d 35, chromium oxide was added to diets at a level of 2 g/kg as an indigestible marker to determine AID of DM and energy (E), according to the methods of AOAC (2000) and N with a Kjeltec™ 2300 (FOSS, Based on Tecator™ technology) Nitrogen Analyser. Ca and P contents were determined according to AOAC (1990) methods. At the end of the experiment, 160 birds (40 birds/treatment and 4 birds/cage) were slaughtered (by cutting carotid arteries) and a portion of the small intestine from Meckel's diverticulum proximal to the ileocecal junction as ileal samples was collected for AID. Chromium levels were determined via UV absorption spectrophotometry (Shimadzu, UV- 1201, Japan) according to a method of Williams et al. (1962). The AID was then calculated relative to chromium concentration (Sales and Janssens, 2003). On d 35, approximately 4 ml of blood samples of 40 broilers from each treatment (4 broilers/cage) were collected from the wing vein into vacuum tube or a K3EDTA vacuum tube and were centrifuged at 4000 g for 15 min at 4°C and serum sample was collected and stored at −4°C until analysis. Blood urea nitrogen (BUN) and serum creatinine concentrations were analysed using an automatic (Boehringer Mannheim, Hitachi 747, Japan) biochemistry blood analyser (Balamuralikrishnan et al., 2017). To determine ileum digesta viscosity, samples of 40 broilers from each treatment (4 broilers/cage) were collected from the ileum on d 35. The liquid fraction of digesta samples was centrifuged at 3500×g for 10 min at 23°C (Lee et al., 2003). Viscosity was determined by adding 0.5 mL of supernatant to a Brookfield Digital Viscometer (Model DV-II, Brookfield Engineering Laboratories Inc., Stoughton, MA) using Cone and Plate Viscometer with a cP-40 spindle at 12 rpm and 40°C to represent the internal temperature of a chicken. Viscosity readings were recorded after 30 sec and results were measured in centipoise (ctp). At the end of the experiment, fresh excreta samples (300 g) were collected from each replication for the analysis of noxious gas emission [ammonia (NH3), hydrogen sulfide (H2S), and total mercaptans (R.SH)] according to the method described by Balamuralikrishnan et al. (2017). Statistical Analysis All data were subjected to statistical analyses in a randomised complete block design using general linear model procedures of SAS/STAT (Statistical Analysis System, version 9.2, SAS Institute Inc., Cary, NC, USA) with a pen as the experimental unit. Mean values and standard errors of the mean were reported. Linear and quadratic polynomial contrasts were performed to determine the effect of β-mannanase at inclusion levels in the diet. Statistical significance was considered when P value was less than 0.05. RESULTS Dietary supplementation of β-mannanase improved ADG (linear and quadratic, P = 0.001, 0.037, respectively) and reduced FCR (linear, P = 0.004) during d1-18; ADG (P = 0.019) d19-35. Overall β-mannanase supplementation improved ADG (linear and quadratic, P = <0.001, 0.049, respectively) and FCR (P = 0.009), but had not on ADFI (Table 2). A linear reduction in ileal digesta viscosity (P = 0.001) with a dietary increase in the level of β-mannanase supplementation was observed (Table 3). Apparent ileal digestibility of DM (P = 0.023), N (P = 0.048) and E (P = 0.001) showed a linear increase with an increase in dietary β-mannanase level, however, there was no effects of β-mannanase on Ca or P digestibility. There were no effects of β-mannanase supplementation on blood creatinine, BUN and excreta noxious gases (NH3, H2S, R.SH) emission during entire experiment (Table 4). Table 2. Growth performance of broilers fed diets supplemented with β-mannanase.1 Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 2. Growth performance of broilers fed diets supplemented with β-mannanase.1 Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 3. Ileal digesta viscosity and apparent ileal digestibility in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758    Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 3. Ileal digesta viscosity and apparent ileal digestibility in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758    Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 4. Blood metabolic profiles and excreta noxious gas emission in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439    Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439  1Each mean represents values from 10 replicates (15 birds/replicate). View Large Table 4. Blood metabolic profiles and excreta noxious gas emission in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439    Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439  1Each mean represents values from 10 replicates (15 birds/replicate). View Large DISCUSSION The broiler industry is fronting several challenges, which has increased attention in the potential use of feed enzymes. Data from this study revealed that inclusion of β-mannanase into corn-SBM based diet significantly increased weight gain and improved feed efficiency, which is in agreement with previous reports (Zou et al., 2006; Muhammad et al., 2015; Ferreira et al., 2016). Similarly, Li et al. (2010) and Kong et al. (2011) reported improvements in ADG of birds fed diet supplemented with β-mannanase. Such results might be due to the beneficial effect of β-mannanase in reducing action of mannan, improvement of nutrients absorption by release of encapsulated nutrients by breakdown of the cell wall matrix, decrease of digesta viscosity (Mehri et al., 2010) and more effective in ameliorating the anti-nutritive NSP of the corn-SBM based diet (Chegeni et al., 2011). On the other hand, Odetallah et al. (2002) designated that β-mannanase also enhanced feed efficiency of turkey. In the present trial, a modified source of β-mannanase was applied. Most fungal β-mannanases have pH optima of 2.4 to 6.0 making them promising candidates for use in the animal feed industry (Cai et al., 2011), which are in agreement with our study inclusion of β-mannanases from fungal improved the growth performance and digestibility. The mechanism through which the improvements were obtained appeared to be related to enhancements in nutrient digestibility (Lv et al., 2013). Increased intestinal viscosity has been shown to have negative effects on nutrient utilisation with high viscous ingredient diets (Latham et al., 2016; 2018). Beta-mannans are highly viscous and may have adverse effects on the digestive system that are overcome with the enzyme. The mode of action of β-mannanase includes improvement in the reduction of digesta viscosity by producing mannan oligosaccharide (Jackson et al., 2004; Saenphoom et al. 2013). Digesta viscosity decreased by enzyme supplementation is presumably responsible for the effect of enzyme supplementation on digesta DM (Gunal and Yasar, 2004; Tahir et al., 2005; Mehri et al., 2010). Some previous studies reported that β-mannanase supplementation can significantly decrease digesta viscosity and increased growth performance of broilers (Lee et al., 2003; Saenphoom et al., 2013). In agreement with these studies, our results also revealed that dietary β-mannanase significantly reduced digesta viscosity which resulted in increased growth performance and ileal digestibility of DM, E, and N. An improvement in broiler performances might be due to improved digestibility associated with reduced β-mannan intake. Additional probable mechanism through which β-mannanase may subsidize to improvements in digestibility when they occur is through an increase in digestive enzyme activity. Similarly, Kong et al. (2011) and Azarfar (2013) have reported that inclusion of exogenous enzymes in diets can affect the digesta viscosity and ileal digestibility of DM and N in broilers. Mok et al. (2013) reported that supplementation of β-mannanase can increase ileal digestibility of DM and E not in P digestibility. On the other hand, Latham et al. (2016) have reported that no effect on ileal digestible E or viscosity of broilers fed inclusion of β-mannanase. Such inconsistency might be due to a different quantity of substrates, feed ingredients, fermentation method, the dosage of β-mannanase and different organisms including bacteria, yeasts, fungi and different strain in different studies. Reduction in BUN may reflect better amino acid retention in the body or lower intestinal absorption of digestible amino acid. Our results were in agreement Jo et al., (2012), Cho and Kim (2013) and Upadhaya et al. (2016) who observed that β-mannanase supplementation had no effect on BUN and no significant difference in noxious gas emissions. In conclusion, results obtained in the present study revealed that β-mannanase supplementation in broiler diets has potential to improve the performance and AID with reduced ileal digesta viscosity in the corn-SBM based diet. Therefore, dietary β-mannanase inclusion should be considered as an alternative solution to the enhancement of performance for the poultry industry. REFERENCES AOAC. 2000. Official Methods of Analysis . 18th Rev. 2 ed. AOAC Int., Gaithersburg MD. AOAC. 1990. Official Methods of Analysis . 15th ed. AOAC Int., Washington DC. Azarfar A. 2013. 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Google Scholar CrossRef Search ADS PubMed  © 2018 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 Poultry Science Oxford University Press

Inclusion of dietary β-mannanase improves performance and ileal digestibility and reduces ileal digesta viscosity of broilers fed corn-soybean meal based diet

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Oxford University Press
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© 2018 Poultry Science Association Inc.
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0032-5791
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10.3382/ps/pey157
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Abstract

ABSTRACT This study was aimed to evaluate the influence of dietary β-mannanase inclusion on growth performance, apparent ileal digestibility, digesta viscosity, blood metabolites and excreta noxious gas emissions in broilers fed corn-soybean meal based diet. A total of 600 conventional healthy 1-d-old ROSS 308 broilers with body weight 45 ± 0.50 g (mean ± SD) were randomly assigned to 4 dietary treatments with 10 replicates cages, with 15 broilers in each and fed basal diet supplemented to corn-SBM based diets with 0, 2400, 4800, and 7200 MNU β-mannanase/kg for 35 d feeding trial period. Significant results were observed on improved average daily gain and reduced feed conversion ratio during trial period and also reduced ileal digesta viscosity and improved apparent ileal digestibility of dry matter, nitrogen and energy. However, no significant effects were found on blood urea nitrogen and creatinine, excreta noxious gas emissions. In conclusion, the inclusion of dietary β-mannanase had potential to improve daily gain and feed efficiency and apparent ileal digestibility while decreasing digesta viscosity of broiler. INTRODUCTION Soybean meal (SBM) is a major protein source and one of the valued ingredients in poultry feeds. The corn-SBM based poultry diets account for 15–34% of total non-starch polysaccharides (NSP) contents of the diet and help to increase the viscosity of digesta, modify the physiology of the gastrointestinal tract and change the ecosystem in the gut (Jackson et al., 1999). Exogenous addition of enzymes was required as the digestive tract of poultry lack the enzymes targeting β-1,4-mannosyl; in turn limiting the nutrient and energy digestibility and growth performance (Jackson et al., 2004). Barros et al. (2015) observed that β- mannanase is responsible for the hydrolysis of β-mannans, thus reducing intestinal viscosity and promoting better nutrient digestibility. Beneficial effects of the inclusion of a β-mannanase in broilers fed diets containing SBM for the enzymatic degradation of β-mannan was reported (Daskiran et al., 2004). During the past few years, β-mannanase has been purified and characterised from various organisms collectively known as mannan degraders (Dhawan and Kaur, 2007). The present study was designed to determine effects of β-mannanase (from Trichoderma citrinoviride) in corn-SBM based diet on growth performances, ileal digesta viscosity, apparent ileal digestibility (AID), blood metabolites and excreta noxious gas emissions in broilers. MATERIALS AND METHODS The protocol for the experiments was approved and birds were maintained according to the guidelines of the Animal Care and Use Committee of Dankook University, Cheonan, South Korea. Source of β-mannanase The commercial exogenous enzyme, β-mannanase (DigeGrain M, Advanced Enzymes Technologies Ltd. Thane (W), India) was produced by controlled fermentation of Trichoderma citrinoviride and contained 24,000,000 β-mannanase units (MNU)/kg. One unit of β-mannanase is the amount of enzyme, which liberates 1 μmol of total reducing sugar (glucose equivalent) from mannan substrate (Locust bean gum) per minute at pH 5.3 and 50°C. This product is extremely effective in hydrolyzing mannan and is stable up to 85°C. Experimental Design, Birds and Husbandry A total of 600 conventional healthy 1-d old Ross 308 broiler chicks (mixed gender) having average BW of 45 ± 0.50 g (mean ± SD) were used in the experiment which lasted for 35 days. Chicks were randomly allotted into one of four treatment diets (10 replicate cages/treatment, 15 chickens/cage). Chickens were grown in a room of 33±1°C for the first 3 days and the temperature was reduced gradually until 24°C maintaining humidity around 60% for the rest of the experiment. Stainless steel cages (1.75 × 1.55 m) of identical size were managed for chickens housing and with free access to feed and water. Diets fed to chickens were: CON (basal diet), basal diet supplemented with 2400, 4800, and 7200 MNU β-mannanase/kg diet. The basal diets were formulated to meet or exceed the nutritional requirements of broilers during starter (d 0 to 18) and finisher (d 19 to 35) phases, according to NRC (1994) recommendations for broiler chickens (Table 1). Table 1. Ingredient composition of experimental diets (as-fed basis). Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  †Provided per kg of complete diet: 11,025 IU vitamin A; 1103 IU vitamin D3; 44 IU vitamin E; 4.4 mg vitamin K; 8.3 mg riboflavin; 50 mg niacin; 4 mg thiamine; 29 mg d-pantothenic; 166 mg choline; 33 μgvitamin B12. ‡Provided per kg of complete diet: 12 mg Cu (as CuSO4•5H2O); 85 mg Zn (as ZnSO4); 8 mg Mn (as MnO2); 0.28 mg I (as KI); 0.15 mgSe (as Na2SeO3•5H2O). §Ether extract represents total fat content in the diet. View Large Table 1. Ingredient composition of experimental diets (as-fed basis). Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  Ingredients, g/kg  Starter (0–18 d)  Finisher (19–35 d)  Corn  547.7  629.1  Soybean meal, CP 48%  288.0  220.0  Corn gluten  95  85  Oil  23  25  Calcium carbonate  10.3  10.3  Dicalcium phosphate  20.0  17.6  Methionine, 99%  2.5  2.1  Lysine, 78.4%  4.5  4.7  Threonine, 98.5%  1.6  0.8  Salt  2.5  1.6  NaHCO3  1.7  1.0  Vitamin premix†  1  1  Mineral premix‡  1  1  Choline, 50%  1.2  0.8  Calculated composition  Metabolisable energy (MJ/kg)  12.56  12.98  Analyzed composition, %  Crude Protein  22.99  20.51  Ether extract§  3.84  3.68  Calcium  0.96  0.889  Available phosphorus  0.48  0.434  Digestible lysine  1.307  1.155  Digestible methionine  0.645  0.570  Dig. met-cys  0.984  0.878  Beta-mannan  1.6  1.5  †Provided per kg of complete diet: 11,025 IU vitamin A; 1103 IU vitamin D3; 44 IU vitamin E; 4.4 mg vitamin K; 8.3 mg riboflavin; 50 mg niacin; 4 mg thiamine; 29 mg d-pantothenic; 166 mg choline; 33 μgvitamin B12. ‡Provided per kg of complete diet: 12 mg Cu (as CuSO4•5H2O); 85 mg Zn (as ZnSO4); 8 mg Mn (as MnO2); 0.28 mg I (as KI); 0.15 mgSe (as Na2SeO3•5H2O). §Ether extract represents total fat content in the diet. View Large Sampling and Measurements Feed samples were ground to pass through a 1-mm screen, after which they were analysed for dry matter (DM, method 934.01; AOAC, 2000), nitrogen (N, method 968.06; AOAC, 2000), ether extract (method 920.39; AOAC, 2000). Individual amino acid (AA) composition was measured using an AA analyser (Beckman 6300; Beckman Coulter Inc., Fullerton, CA) after a 24 h hydrolysis in HCl (Spackman et al. 1958). For the determination of Cys and Met, the samples were oxidised with performic acid overnight at 0°C (Moore, 1963). Nitrogen was determined using Kjectec 2300 Nitrogen Analyzer (Foss Tecator AB, Hoeganaes, Sweden), and crude protein was calculated as N × 6.25. Test ingredients were hydrolyzed with 72% (w/w) H2SO4 for 1 h, diluted with distilled water to final concentration of H2SO4 at 1 N and incubated at 121°C for 45 min to determine mannan content. Mannan contents in the hydrolysates were determined using an evaporative light scattering detector and a Shodex sugar column SP0810 (8.0 mm × 300 mm; Showa Denko K.K., Tokyo, Japan) according to the procedures described by Mok et al., (2013). Broilers were weighed, and feed intake was recorded at d 1, d 18, and d 35. Average daily gain (ADG), average daily feed intakes (ADFI), and feed conversion ratio (FCR, pen basis) were determined for each phase. From d 29 to d 35, chromium oxide was added to diets at a level of 2 g/kg as an indigestible marker to determine AID of DM and energy (E), according to the methods of AOAC (2000) and N with a Kjeltec™ 2300 (FOSS, Based on Tecator™ technology) Nitrogen Analyser. Ca and P contents were determined according to AOAC (1990) methods. At the end of the experiment, 160 birds (40 birds/treatment and 4 birds/cage) were slaughtered (by cutting carotid arteries) and a portion of the small intestine from Meckel's diverticulum proximal to the ileocecal junction as ileal samples was collected for AID. Chromium levels were determined via UV absorption spectrophotometry (Shimadzu, UV- 1201, Japan) according to a method of Williams et al. (1962). The AID was then calculated relative to chromium concentration (Sales and Janssens, 2003). On d 35, approximately 4 ml of blood samples of 40 broilers from each treatment (4 broilers/cage) were collected from the wing vein into vacuum tube or a K3EDTA vacuum tube and were centrifuged at 4000 g for 15 min at 4°C and serum sample was collected and stored at −4°C until analysis. Blood urea nitrogen (BUN) and serum creatinine concentrations were analysed using an automatic (Boehringer Mannheim, Hitachi 747, Japan) biochemistry blood analyser (Balamuralikrishnan et al., 2017). To determine ileum digesta viscosity, samples of 40 broilers from each treatment (4 broilers/cage) were collected from the ileum on d 35. The liquid fraction of digesta samples was centrifuged at 3500×g for 10 min at 23°C (Lee et al., 2003). Viscosity was determined by adding 0.5 mL of supernatant to a Brookfield Digital Viscometer (Model DV-II, Brookfield Engineering Laboratories Inc., Stoughton, MA) using Cone and Plate Viscometer with a cP-40 spindle at 12 rpm and 40°C to represent the internal temperature of a chicken. Viscosity readings were recorded after 30 sec and results were measured in centipoise (ctp). At the end of the experiment, fresh excreta samples (300 g) were collected from each replication for the analysis of noxious gas emission [ammonia (NH3), hydrogen sulfide (H2S), and total mercaptans (R.SH)] according to the method described by Balamuralikrishnan et al. (2017). Statistical Analysis All data were subjected to statistical analyses in a randomised complete block design using general linear model procedures of SAS/STAT (Statistical Analysis System, version 9.2, SAS Institute Inc., Cary, NC, USA) with a pen as the experimental unit. Mean values and standard errors of the mean were reported. Linear and quadratic polynomial contrasts were performed to determine the effect of β-mannanase at inclusion levels in the diet. Statistical significance was considered when P value was less than 0.05. RESULTS Dietary supplementation of β-mannanase improved ADG (linear and quadratic, P = 0.001, 0.037, respectively) and reduced FCR (linear, P = 0.004) during d1-18; ADG (P = 0.019) d19-35. Overall β-mannanase supplementation improved ADG (linear and quadratic, P = <0.001, 0.049, respectively) and FCR (P = 0.009), but had not on ADFI (Table 2). A linear reduction in ileal digesta viscosity (P = 0.001) with a dietary increase in the level of β-mannanase supplementation was observed (Table 3). Apparent ileal digestibility of DM (P = 0.023), N (P = 0.048) and E (P = 0.001) showed a linear increase with an increase in dietary β-mannanase level, however, there was no effects of β-mannanase on Ca or P digestibility. There were no effects of β-mannanase supplementation on blood creatinine, BUN and excreta noxious gases (NH3, H2S, R.SH) emission during entire experiment (Table 4). Table 2. Growth performance of broilers fed diets supplemented with β-mannanase.1 Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 2. Growth performance of broilers fed diets supplemented with β-mannanase.1 Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  Traits  Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Day 1–18  ADG, g  722b  753a  754a  762a  5.25  <0.001  0.037  ADFI, g  1089  1085  1090  1090  7.50  0.866  0.786  FCR  1.509a  1.442b  1.444b  1.430b  0.02  0.004  0.112  Day 19–35  ADG, g  892b  916a,b  922a  926a  9.41  0.019  0.302  ADFI, g  1400  1418  1412  1401  17.55  0.962  0.422  FCR  1.569  1.551  1.531  1.513  0.02  0.090  0.998  Overall  ADG, g  1614b  1668a  1677a  1688a  10.23  <0.001  0.049  ADFI, g  2489  2502  2501  2490  19.57  0.975  0.536  FCR  1.542a  1.501a,b  1.492a,b  1.476b  0.02  0.009  0.467  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 3. Ileal digesta viscosity and apparent ileal digestibility in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758    Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 3. Ileal digesta viscosity and apparent ileal digestibility in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758    Dietary β-mannanase levels (MNU/kg)  SEM  P-Value    0  2400  4800  7200    Linear  Quadratic  Ileal viscosity, ctp  4.84b  4.54a,b  4.27a,b  4.24a  0.11  < 0.001  0.244  Apparent ileal digestibility, g/kg                Dry matter  0.69b  0.70b  0.70b  0.72a  0.31  0.023  0.360  Nitrogen  0.72b  0.74a,b  0.75a,b  0.75a  0.41  0.048  0.930  Energy  0.71b  0.73a,b  0.73a,b  0.74a  0.24  < 0.001  0.187  Ca  0.60  0.61  0.61  0.61  0.49  0.203  0.720  P  0.46  0.47  0.47  0.47  1.07  0.512  0.758  1Each mean represents values from 10 replicates (15 birds/replicate). a,bMeans in the same row with different superscripts differ (P < 0.05). View Large Table 4. Blood metabolic profiles and excreta noxious gas emission in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439    Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439  1Each mean represents values from 10 replicates (15 birds/replicate). View Large Table 4. Blood metabolic profiles and excreta noxious gas emission in broilers fed diets supplemented with β-mannanase.1   Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439    Dietary β-mannanase levels (MNU/kg)  SEM  P-value    0  2400  4800  7200    Linear  Quadratic  Blood metabolites  BUN, mmol/l  1.03  1.03  1.06  1.06  0.13  0.612  0.974  Creatinine, μmol/l  17.68  15.03  19.45  15.91  0.01  0.711  0.830  Excreta noxious gas emission, mg/kg                NH3  3.05  3.07  3.07  3.06  0.2  0.731  0.517  H2S  2.0  2.0  2.3  2.5  0.2  0.148  0.734  Total mercaptans  1.2  1.2  1.4  1.2  0.1  0.616  0.439  1Each mean represents values from 10 replicates (15 birds/replicate). View Large DISCUSSION The broiler industry is fronting several challenges, which has increased attention in the potential use of feed enzymes. Data from this study revealed that inclusion of β-mannanase into corn-SBM based diet significantly increased weight gain and improved feed efficiency, which is in agreement with previous reports (Zou et al., 2006; Muhammad et al., 2015; Ferreira et al., 2016). Similarly, Li et al. (2010) and Kong et al. (2011) reported improvements in ADG of birds fed diet supplemented with β-mannanase. Such results might be due to the beneficial effect of β-mannanase in reducing action of mannan, improvement of nutrients absorption by release of encapsulated nutrients by breakdown of the cell wall matrix, decrease of digesta viscosity (Mehri et al., 2010) and more effective in ameliorating the anti-nutritive NSP of the corn-SBM based diet (Chegeni et al., 2011). On the other hand, Odetallah et al. (2002) designated that β-mannanase also enhanced feed efficiency of turkey. In the present trial, a modified source of β-mannanase was applied. Most fungal β-mannanases have pH optima of 2.4 to 6.0 making them promising candidates for use in the animal feed industry (Cai et al., 2011), which are in agreement with our study inclusion of β-mannanases from fungal improved the growth performance and digestibility. The mechanism through which the improvements were obtained appeared to be related to enhancements in nutrient digestibility (Lv et al., 2013). Increased intestinal viscosity has been shown to have negative effects on nutrient utilisation with high viscous ingredient diets (Latham et al., 2016; 2018). Beta-mannans are highly viscous and may have adverse effects on the digestive system that are overcome with the enzyme. The mode of action of β-mannanase includes improvement in the reduction of digesta viscosity by producing mannan oligosaccharide (Jackson et al., 2004; Saenphoom et al. 2013). Digesta viscosity decreased by enzyme supplementation is presumably responsible for the effect of enzyme supplementation on digesta DM (Gunal and Yasar, 2004; Tahir et al., 2005; Mehri et al., 2010). Some previous studies reported that β-mannanase supplementation can significantly decrease digesta viscosity and increased growth performance of broilers (Lee et al., 2003; Saenphoom et al., 2013). In agreement with these studies, our results also revealed that dietary β-mannanase significantly reduced digesta viscosity which resulted in increased growth performance and ileal digestibility of DM, E, and N. An improvement in broiler performances might be due to improved digestibility associated with reduced β-mannan intake. Additional probable mechanism through which β-mannanase may subsidize to improvements in digestibility when they occur is through an increase in digestive enzyme activity. Similarly, Kong et al. (2011) and Azarfar (2013) have reported that inclusion of exogenous enzymes in diets can affect the digesta viscosity and ileal digestibility of DM and N in broilers. Mok et al. (2013) reported that supplementation of β-mannanase can increase ileal digestibility of DM and E not in P digestibility. On the other hand, Latham et al. (2016) have reported that no effect on ileal digestible E or viscosity of broilers fed inclusion of β-mannanase. Such inconsistency might be due to a different quantity of substrates, feed ingredients, fermentation method, the dosage of β-mannanase and different organisms including bacteria, yeasts, fungi and different strain in different studies. Reduction in BUN may reflect better amino acid retention in the body or lower intestinal absorption of digestible amino acid. Our results were in agreement Jo et al., (2012), Cho and Kim (2013) and Upadhaya et al. (2016) who observed that β-mannanase supplementation had no effect on BUN and no significant difference in noxious gas emissions. In conclusion, results obtained in the present study revealed that β-mannanase supplementation in broiler diets has potential to improve the performance and AID with reduced ileal digesta viscosity in the corn-SBM based diet. Therefore, dietary β-mannanase inclusion should be considered as an alternative solution to the enhancement of performance for the poultry industry. REFERENCES AOAC. 2000. Official Methods of Analysis . 18th Rev. 2 ed. AOAC Int., Gaithersburg MD. AOAC. 1990. Official Methods of Analysis . 15th ed. AOAC Int., Washington DC. Azarfar A. 2013. 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Poultry ScienceOxford University Press

Published: May 16, 2018

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