Evaluation And Prediction Of Standardized Ileal Digestible Amino Acid And Metabolizable Energy Content Of Wheat And Cottonseed Meal For Broiler Chickens

Two experiments were conducted to determine the chemical composition,standard ileal amino acid digestibility and metabolic energy of wheat and cottonseed meal from different origins for broiler chickens,to evaluate the improvement of wheat nutritional value by adding xylanase to wheat diet,and to establish the prediction equation of amino acid digestibility and metabolic energy of cottonseed meal.Exp.1,the chemical composition of 30 wheat samples from the main wheat producing areas of China was analyzed,and the contents of standard ileal digestible amino acids(SID AA)and nitrogen corrected Apparent Metabolizable Energy(AME)of six wheat samples were determined.The effects of exogenous xylanase on SID AA and AME of broilers were also discussed.The results showed that the chemical components of wheat samples from different origins were different,glutamic acid was the dominant amino acid of wheat;except lysine,threonine,phenylalanine and cystine,the SID AA of Gansu wheat was higher than that of other wheat samples(P<0.05),and the AMEn value(11.83 MJ/kg)was significantly higher than that of other wheat samples(P<0.001).The average SID content of essential amino acids and SID non essential amino acids was 87.35%and 88.17%respectively,and the average AME value of six wheat was 11.14 MJ/kg.Compared with the diet without xylanase,the average SID AA value of the diet with xylanase increased by 1.96%,among which the SID contents of methionine,lysine,tryptophan,arginine,isoleucine,leucine,valine,glycine,aspartic acid,glutamic acid,proline and alanine were all higher(P<0.05),and the AME value significantly increased by 0.87 MJ/kg(P<0.05).Exp.2,the chemical composition of the main cottonseed meal samples in China was analyzed.The contents of standard ileal digestible amino acids(SID AA)and nitrogen corrected Apparent Metabolizable Energy(AMEn)in 10 cottonseed meal samples were determined.The linear regression prediction equations between amino acid digestibility and metabolizable energy and conventional chemical components were established.The results showed that the chemical composition of cottonseed meal samples from different origins was significantly different,crude fat content was the most variable chemical composition,and the coefficient of variation was 19.90(P<0.05);Glutamic acid and arginine were the highest and lowest amino acids in cottonseed meal,and the content and composition of amino acids in cottonseed meal were positively correlated with their crude protein content.The apparent amino acids and digestibility of crude protein in Xinjiang cottonseed meal with crude protein content of 63.83%were higher than those of other sources,and the AMEn value was 8.27 MJ/kg;except tryptophan,arginine,phenylalanine,glycine and aspartic acid,Xinjiang cottonseed meal with 43.36%crude protein(CP)had the lowest apparent amino acid digestibility in the ileum,and its AMEn value was 6.93 MJ/kg,with a significant difference(P<0.001).The average digestibility of essential amino acids,nonessential amino acids and total amino acids of 10 cottonseed meal samples were 76.59%,77.21%and 76.90%respectively,and the average AMEn value was 7.57 MJ/kg.SID of CP,Lys,met and thr of cottonseed meal was negatively correlated with fiber components such as neutral detergent fiber(NDF)and acid detergent fiber(ADF),and positively correlated with Lys content;prediction equations of SID CP,SID Lys,SID Met and SID Thr as follow,SID CP=0.68×EE+73.42(R2=0.84),SID Lys=0.39×CP+58.96(R2=0.79),SID Met=2.46×Lys-1.43×NDF+106.33(R2=0.92)and SID Thr=0.28×CP+2.02×NDF+63.17(R2=0.71).AME and AMEn of cottonseed meal were negatively correlated with fiber components such as NDF and ADF.The prediction equations of AME and AMEn were AME=1.83×GE-0.41×NDF+0.28×CP-16.73(R2=0.82)and AME=1.26×GE-0.38×NDF+0.18×CP+12.39(R2=0.89),respectively.In conclusion,the origins of wheat and cottonseed meal have a significant impact on the standard ileal amino acid digestibility and nitrogen corrected metabolic energy of broilers.The differences in chemical composition of wheat and cottonseed meal from different origins,especially the contents of crude protein,crude fat and NDF,may be the main reason for the significant differences in SID AA and AMEn.The nutritional value of wheat can be significantly improved by adding exogenous xylanase.The prediction equations of SID AA and AMEn value of cottonseed meal can be used to predict its nutritional value.