Effects of N-hydroxymethyl methionine calcium on production performance and rumen fermentation of lactating dairy cows

The purpose of this experiment was to study the effects of different levels of N-Hydroxymethyl Methionine Calcium (N-HMM-Ca) on the performance, milk quality and rumen fermentation of lactating Holstein cows. 30 lactating Holstein dairy cows were blocked according parity, milk yield and lactation stage, and randomly assigned to 5 groups, 6 in each group. 0, 0.15%, 0.30%, 0.75%, and 1.50% N-HMM-Ca were added to the diet on a dry matter basis. The experiment was continued up to 56 d, including 14 d of adaptation period and 42 d of experimental period. The results showed: 1) Dietary supplementation of 0.15% N-HMM-Ca significantly increased milk production (P < 0.05). 2) Compared with the control group, the lactose rate and milk protein rate were significantly increased in the range of 0.15% to 0.75% (P < 0.05). 3) The apparent digestibility of Crude protein, Ether extract, Calcium and Phosphorus was not affected by the level of N-HMM-Ca, but the 0.15% group significantly increased the apparent digestibility of ADF and NDF (P < 0.05). 4) There was no significant relationship between the pH, VFA and MCP content of rumen fluid and the level of N-HMM-Ca (P > 0.05). 5) The 0.15% group increased the relative expression of Fibrobacter succinogenes、Ruminococcus albus、R. flavefaciens (P < 0.01). In summary, the addition of 0.15% N-HMM-Ca to the diet of lactating dairy cow can effectively improve the production performance, milk quality, and feed digestion as well as utilization. Therefore, it is recommended to add the N-HMM-Ca to the diet of lactating dairy cow and a suitable dose is 0.15%.