| The reduction substitution of corn and soybean meal is a hot topic of research in the livestock industry in recent years.Different grains and by-products contain a large number of anti-nutritional factors,which can affect the digestibility of nutrients and reduce the growth performance of pigs.Non-starch polysaccharide(NSP)refers to the general name of polysaccharides contained in plants except starch,which is a common anti-nutrition factor in plant feeds.The types and contents of NSP in different feed materials are very different,which brings great challenges to the precise formulation of feed formulas.NSP enzyme is a class of enzyme preparation that can degrade NSP in feed,including xylanase,β-glucanase,α-arabinfuranosidase,etc.Phytic acid is also one of the main anti-nutritional factors in the pig diet,which can reduce the utilization of protein,minerals,and especially phosphorus.Phytase can effectively alleviate the negative effects of phytic acid.In recent years,the price of feed ingredients in China has fluctuated greatly,and often the diets are formulated by using corn,wheat,and other cereal ingredients alternately according to the price,but the NSP and phytate content of different types of diets are different,and the NSP enzyme and phytase required to be added are different.However,there has not been any report on the effect of the additional amount of NSP enzyme and phytase on growing pigs according to different dietary types.Therefore,this study systematically evaluated the nutritional improvement of adding NSP enzyme and phytase to different types of diets for growing pigs,and the results of the study can provide a theoretical basis and data support for the precise formulation of pig diets.This study was conducted in four parts as follows.Part 1: The optimal enzyme addition level of NSP enzyme based on enzymatic hydrolysis method in vitro.This experiment investigated the screening of the optimum addition of NSP enzyme based on a two-part pepsin-trypsin digestion method.Corn,wheat,wheat bran,and soybean meal with inactivated endogenous enzymes were selected as raw materials,and the decomposition effects of different enzymatic activities of xylanase(0,900,1200,1500,1800,and 2100 U/kg),β-glucanase(0,800,1000,1200,and 1400 U/kg)and α-arabinofuranosidase(0,5000,6600,8200,and 9800 U/kg)were determined based on in vitro enzymatic digestion,so as to select the optimal dosage of xylanase,β-glucanase andα-arabinfuranosidase.The results showed that when xylanase was added at 1800 U/kg,the dry matter digestibility of wheat and wheat bran was the highest(P < 0.05);the highest dry matter digestibility and reducing sugar content of corn,wheat and wheat bran were obtained when β-glucanase was added at 1200 U/kg(P < 0.05);the highest dry matter digestibility and reducing sugar content of corn,wheat,wheat bran,and soybean meal were obtained when 6600 U/kg of α-arabinofuranosidase was added(P < 0.05).In summary,based on in vitro enzymatic hydrolysis method,the optimal supplemental levels of NSP enzyme in wheat and wheat bran were 1800 U/kg xylanase,1200 U/kg β-glucanase,and 6600 U/kg α-arabinfuranosidase.Part 2: Effects of NSP enzyme on nutrient digestibility in wheat and wheat byproducts diets of growing pigs.This study determined the effects of NSP enzyme supplementation on nutrient digestibility in wheat and wheat by-products diets of growing pigs.A total of 6 healthy Duroc × Landrace × Landrace hybrid pigs(initial body weight 58.0 ± 1.5 kg)were selected and divided into 6 treatments using a 3 × 2 two-factor experiment design,with the main factors being the level of arabinoxylan in the diet and the addition of NSP enzyme,respectively.A 6 × 6 Latin square design was used to divide pigs into 6 treatments,each treatment was divided into 6 sessions and each session lasted 11 days.The digestibility of total energy,dry matter,organic matter,crude protein,starch,crude fat,and crude fiber was determined by collecting feces and terminal ileal digesta in each period.The results showed that there was a significant negative correlation between dietary arabinoxylan levels and nutrient digestibility(P < 0.05);there was a significant interaction between the addition of NSP enzyme and dietary arabinoxylan levels on total energy digestibility,with the addition of NSP enzyme significantly increasing the total energy digestibility of diets with high levels of arabinoxylan(P < 0.05);the addition of NSP enzyme significantly improved nutrient digestibility,with ileal terminal digestibility of organic matter and crude protein increasing by 3.5% and 3.3%,respectively,and total intestinal digestibility of organic matter,crude protein and energy increasing by 1.2%,1.9%,and 1.6%,respectively(P <0.05);a similar trend was observed for terminal ileal amino acid digestibility,which was increased by 5% in the high arabinoxylan diets(P < 0.05).In conclusion,NSP in wheat and wheat bran diets reduced the digestibility of nutrients in growing pig diets,and the addition of NSP enzyme could improve the digestibility of nutrients.Part 3: Effect of NSP enzyme and phytase complexes on nutrient digestibility in different phytate levels diets of growing pigs.This experiment investigated the effect of NSP enzyme and phytase complexes on the digestibility of nutrients in the terminal ileum and total intestine of growing pigs on diets with different phytate levels.A total of 8 barrows with an initial body weight of 30.7 ± 1.1kg were fitted with T-fistulas at the end of the ileum.The experiment was conducted in a 2× 2 two-way design and randomly divided into 4 treatments,with the main effects of dietary phytate levels and the addition of enzyme complexes,respectively.A total of 8 pigs was conducted by a 4 × 4 Latin square design,with each period lasting 10 d.The enzyme complexes diet contained 1800 U/kg xylanase,1200 U/kg β-glucanase,6600 U/kg α-arabinofuranosidase,and 1000 U/kg phytase.The results showed that compared with the low phytate diet,the apparent ileal digestibility(AID)of crude protein was reduced by 1.4%(P < 0.05),the apparent total tract digestibility(ATTD)of organic matter,crude protein,and total energy were reduced by 1.7%,2.3%,and 1.9%,respectively(P < 0.05),and the ATTD of calcium was reduced by 17.3% in the high phytate diet(P = 0.10);the addition of complexes enzymes to the diets increased the AID of calcium and phosphorus by 34.2%,31.1%,and 26.7% and 41.3% for low and high phytate diets,respectively,and increased the ATTD of crude fat,phosphorus,and calcium by 1.4%,45.6%,9.6%,and 3.1%,66.0%,and 52.7% for low and high phytate diets,respectively(P < 0.05).In conclusion,dietary supplementation of NSP enzyme and phytase complexes can increase the AID and ATTD of crude fat,calcium,and phosphorus in growing pigs.Part 4: Effects of NSP enzyme and phytase complexes supplementation on the growth performance,nutrient digestibility,and intestinal health of growing-finishing pigs.This experiment was conducted to investigate the effects of NSP enzyme and phytase complexes in a corn-wheat-soybean meal diet on the growth performance,nutrient digestibility,meat quality,blood parameters,and intestinal health of growing-finishing pigs.A total of 300 hybrid pigs(Duroc × Landrace × Landrace,initial body weight 25.3 ± 0.7kg)were randomly divided into 3 groups with 10 replicates per group and 10 pigs per replicate.Three groups were fed a basal nutrient level diet(CON),low nutrient level diet(NC),and low nutrient level + complexes enzymes diet(TRT),respectively.The supplementation levels of complexes enzymes in the diet were 1800 U/kg xylanase,1200U/kg β-glucanase,6600 U/kg α-arabinfuranosidase,and 1000 U/kg phytase,respectively.Net energy,digestible amino acid,digestible phosphorus,and calcium in the NC group were decreased by 74 kcal/kg,7.0%,0.13%,and 0.12%,respectively.The experiment was divided into 4 growth stages: stage 1: 25-50 kg,stage 2: 50-75 kg,stage 3: 75-100 kg,and stage 4: 100-135 kg.The results showed that compared with the CON group,the average daily gain,average daily feed intake,and feed to gain ratio of the NC group in the first,second,third,and fourth stages were significantly decreased,and the ATTD of crude protein,crude fat,phosphorus,and calcium were significantly reduced(P < 0.05);in the second,third and fourth stages,the supplementation of complexes enzymes significantly increased the average daily gain,average daily feed intake and feed to gain ratio,and significantly enhanced the ATTD of crude protein,crude fat,ash,phosphorous,and calcium(P < 0.05);the meat quality of pigs in each treatment group was not significantly different,but the eye muscle area of pigs in the TRT group was significantly higher than that in the NC group(P < 0.05);the glucose,total protein,and growth hormone levels of serum in the TRT group were significantly higher than the NC group(P < 0.05),and the enzyme activities of protease,lipase and amylase in duodenal digesta were significantly higher than the CON and NC groups(P < 0.05);in addition,the levels of intestinal mucosal inflammatory factors TNF-α and interleukin 1β in the TRT group were significantly lower than the NC group(P < 0.05);there was no significant difference between the 3 groups in the microbial diversity(P > 0.05).In conclusion,the supplementation of NSP enzyme and phytase complexes in the corn-wheat-soybean meal basal diet can improve the growth performance,nutrient digestibility,and digestive enzyme activities,reduce the level of inflammation,and have no negative effects on the meat quality of finishing pigs.Conclusion: 1)the optimal supplemental levels of NSP enzyme were as follows:xylanase 1800 U/kg,β-glucanase 1200 U/kg,α-arabinfuranosidase 6600 U/kg supplemented in wheat and wheat bran,based on in vitro enzymatic hydrolysis method;2)the digestibility of crude protein,crude fat,and starch of growing pigs could be improved by adding NSP enzyme to wheat and by-product diets enriched in NSP;3)the digestibility of crude fat,calcium,and phosphorous of growing pigs could be increased by adding the NSP enzyme and phytase complex to corn-rice bran diet enriched in phytate;4)the growth performance,nutrient digestibility,and meat quality of growing-finishing pigs fed on basal diets can be achieved by adding NSP enzyme and phytase complexes to low-nutrient diets. |
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