This study was conducted to evaluate the effects of dietary crude protein(CP)and rumen-protected lysine(RPL)supplementation on lactation performance,amino acid(AA)balance,nitrogen(N)utilization and hindgut microbiota ...This study was conducted to evaluate the effects of dietary crude protein(CP)and rumen-protected lysine(RPL)supplementation on lactation performance,amino acid(AA)balance,nitrogen(N)utilization and hindgut microbiota in dairy cows.Treatments were in a 2×2 factorial arrangement,and the main effects were CP concentration(16%vs.18%)and RPL supplementation(with or without RPL at40 g/cow per day).Forty cows were randomly allocated to 4 groups:low-CP diet(LP),low-CP diet plus RPL(LPL),high-CP diet(HP),high-CP diet plus RPL(HPL).The experiment was conducted for 8 weeks.Results showed that RPL increased the dry matter intake(P<0.01),milk protein yield(P=0.04)and energy corrected milk(P=0.04),and tended to increase milk fat yield(P=0.06)and fat corrected milk(P=0.05).Cows in the HP group tended to have higher milk urea N(P=0.07).Plasma concentrations of Arg,Ile,Lys,Met,Pro,total essential AA and total nonessential AA were increased by RPL(P<0.05).The total essential AA,total nonessential AA and most AA(except Ile,Phe,Gly and Pro)were increased in the HP group(P<0.05).N excretion was increased in the HP group through an increase in urea N excretion(P<0.01)and an upward trend in plasma urea N(P=0.07).In addition,RPL tended to increase milk protein N secretion(P=0.08),milk N(P=0.07)and microbial protein synthesis(P=0.06),and decreased plasma urea N(P<0.001).In the hindgut,the bacterial community were different between the LP and LPL groups(P<0.01).The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL(P=0.03 and 0.03,respectively).The pathogenic abundances of Clostridium_sensu_stricto_1(P<0.001)and Turicibacter(P<0.01)were decreased by RPL.In conclusion,supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield,resulting in an improvement in N utilization efficiency,and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.展开更多
基金financially supported by National Natural Science Foundation of China (32172742 and 32202688)the Natural Science Foundation of Zhejiang Province (LQ22C170002)+1 种基金the Zhejiang Provincial Science and Technology Plan Project(2022C04038)the Zhejiang Animal Husbandry Industry Technology Project
文摘This study was conducted to evaluate the effects of dietary crude protein(CP)and rumen-protected lysine(RPL)supplementation on lactation performance,amino acid(AA)balance,nitrogen(N)utilization and hindgut microbiota in dairy cows.Treatments were in a 2×2 factorial arrangement,and the main effects were CP concentration(16%vs.18%)and RPL supplementation(with or without RPL at40 g/cow per day).Forty cows were randomly allocated to 4 groups:low-CP diet(LP),low-CP diet plus RPL(LPL),high-CP diet(HP),high-CP diet plus RPL(HPL).The experiment was conducted for 8 weeks.Results showed that RPL increased the dry matter intake(P<0.01),milk protein yield(P=0.04)and energy corrected milk(P=0.04),and tended to increase milk fat yield(P=0.06)and fat corrected milk(P=0.05).Cows in the HP group tended to have higher milk urea N(P=0.07).Plasma concentrations of Arg,Ile,Lys,Met,Pro,total essential AA and total nonessential AA were increased by RPL(P<0.05).The total essential AA,total nonessential AA and most AA(except Ile,Phe,Gly and Pro)were increased in the HP group(P<0.05).N excretion was increased in the HP group through an increase in urea N excretion(P<0.01)and an upward trend in plasma urea N(P=0.07).In addition,RPL tended to increase milk protein N secretion(P=0.08),milk N(P=0.07)and microbial protein synthesis(P=0.06),and decreased plasma urea N(P<0.001).In the hindgut,the bacterial community were different between the LP and LPL groups(P<0.01).The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL(P=0.03 and 0.03,respectively).The pathogenic abundances of Clostridium_sensu_stricto_1(P<0.001)and Turicibacter(P<0.01)were decreased by RPL.In conclusion,supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield,resulting in an improvement in N utilization efficiency,and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.
