Effects Of Rumen-protected Methionine And Rumen-protected Leucine Supplemented In Low Protein Diet On Production Performance Of Lactating Dairy Holstein Cows

This experiment was conducted to study the effects of rumen-protected methionine and rumen-protected leucine on the performance of lactating dairy cows fed low-protei-n soybean meal diets and explore the ways of their effects.Sixty Chinese holstein cows were blocked by days in milk,milk yield,and parity,and randomly assigned to1 of the following 4 treatments: HP group(17.13% CP),LP group(14.10% CP),M group(14.10% CP + RPMet 7.83g/d),L group(14.10% CP + RPMet 7.83g/d),L group(14.10% CP + RPU 36.01g/d),ML group(14.10% CP + RPMet 7.83g/d).+ RP Leu 36.01g/d.The experiment included 2-wk pre-feeding period and 7-wk trial period.The milk yield,milk index,serum amino acid level,serum hormone level,serum biochemical index and changes of mammary gland signaling pathway of dairy cows in each group were detected according to the experimental design.The results showed that milk yield of HP group was significantly higher than that of other four groups,milk yield of M group and ML group was significantly higher than that of LP group and L group(P < 0.01),milk yield of group L and group LP had no significant difference,milk protein rate of group M and group ML was significantly higher than that of group HP,group LP and group L(P < 0.01),milk protein rate of group HP,group LP and group L had no significant difference.The milk protein production in group ML was significantly higher than that in group LP(P=0.03);Serum Leu concentration in HP group was significantly higher than that in the other four groups.There was no significant difference in serum Leu concentration between the other four groups by diet.The serum levels of Met in HP group,group M and group ML were significantly higher than those in group LP and group L(P< 0.01).There were no significant differences in serum insulin,glucagon,IGF-I,prolactin,growth hormone and NO in each group.The serum levels of alanine amino transferase in group ML were significantly lower than those in the other four groups(P = 0.02).There was no difference in the phosphorylation level of mTOR proteinamong groups,but the phosphorylation level of eEF2 in group ML and group L decreased,and the corresponding casein synthesis rate increased.We concluded that rumen methionine supplementation in low protein soybean meal diet could increase milk yield,milk protein rate and milk protein yield of dairycows,affect blood amino acid level,decrease phosphorylation level of eEF2,but could not affect blood hormone and mTOR phosphorylation level;rumen leucine supplementation in low protein soybean meal diet could increase milk yield,milk protein rate and milk protein yield of dairy cows.Acids had no effect on milk yield and milk protein percentage of dairy cows,and could not affect the phosphorylation levels of blood amino acids,blood hormones,mTOR protein and eEF2 protein.