低蛋白质饲粮补充过瘤胃赖氨酸和过瘤胃蛋氨酸对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响

本试验旨在研究低蛋白质饲粮补充过瘤胃赖氨酸(RPLys)和过瘤胃蛋氨酸(RPMet)对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响.选取36头健康无疾病的荷斯坦公牛,随机分为3组,每组12头牛.对照组(Ⅰ组)饲喂蛋白质水平为13％的正常饲粮,2个试验组(Ⅱ、Ⅲ组)均饲喂蛋白质水平为11％的低蛋白质饲粮,同时Ⅱ组补...

Effects of Low Protein Diet Supplemented with Rumen-Protected Lysine and Rumen-Protected Methionine on Growth Performance,Slaughter Performance,Meat Quality and Nitrogen Metabolism of Holstein Bulls

The purpose of this experiment was to study the effects of low protein diet supplemented with rumenprotected lysine(RPLys)and rumen-protected methionine(RPMet)on growth performance,slaughter performance,meat quality and nitrogen metabolism of Holstein bulls. Thirty-six healthy Holstein bulls were randomly divided into 3 groups with 12 replicates per group and one Holstein bull for each replicate. Holstein bulls in control group(groupⅠ)was fed a normal diet with the protein level of 13%,and those in test groups(groupsⅡandⅢ)were fed a low protein diet with the protein level of 11% and supplemented with 34 g/(d·head)RPLys +2 g/(d·head)RPMet(groupⅡ)and 55 g/(d·head)RPLys+9 g/(d·head)RPMet(groupⅢ),respectively. The experiment included a 7-day pre-test period and an 83-day formal test period. The results showed as follows:1)there were no significant differences in growth performance,nutrient apparent digestibility and slaughter performance of Holstein bulls among groups(P>0.05). 2)There were no significant differences in muscle pH,shear force,drop loss,dehydration rate,meat color and conventional nutrient contents in muscle of Holstein bulls among groups(P>0.05). 3)The content of isoleucine(Ile)in muscle of groupⅢwas extremely significantly higher than that of groupⅠ(P<0.01),and the contents of glutamic acid(Glu)and aspartic acid(Asp)were significantly higher than those of groupⅠ(P<0.05);the free threonine(Thr)content in serum of groupⅢwas extremely significantly higher than that of groupsⅠandⅡ(P<0.01),the contents of free total amino acids,phenylalanine(Phe)and alanine(Ala)in muscle were significantly higher than those of groupsⅠandⅡ(P<0.05),the content of free lysine(Lys)was significantly higher than that of groupⅠ(P<0.05),and the content of free glycine(Gly)was significantly higher than that of groupⅡ(P<0.05). 4)For nitrogen metabolism related genes in muscle,compared with groupⅠ,the mRNA relative expression level of insulin receptor substrate 1(IRS1)of groupsⅡandⅢwas extremely significantly increased(P<0.01);the mRNA relative expression levels of tuberous sclerosis complex 1(TSC1)and tuberous sclerosis complex 2(TSC2)of groupⅢwas extremely significantly reduced(P<0.01),and the mRNA relative expression level of phosphatidylinositol-3-kinase(PI3 K)was significantly increased(P < 0. 05);the mRNA relative expression levels of solute carrier family 3,member 2(SLC3 A2),phosphoinositide-dependent protein kinase(PDK),ribosomal protein S6 kinase 1(S6 K1),recombinant eukaryotic translation initiation factor 4 B(eIF4 B)and recombinant eukaryotic translation initiation factor 4 E-binding protein 1(eIF4 EBP1)had no significant differences among groups(P>0.05). In conclusion,when the dietary protein level is reduced from 13% to 11%,supplementation of55 g/(d·head)RPLys+9 g/(d·head)RPMet in the diet can not affect the growth performance,nutrient apparent digestibility,slaughtering performance and muscle quality of Holstein bulls,and can improve the expression of genes related to nitrogen metabolism in muscle.[Chinese Journal of Animal Nutrition,2022,34(2):1014-1026]