Studies of the effect of supplementing protected methionine (HMM-Ca) to dairy cows on milk yield and fertility

A trial with 90 cows was conducted to examine the effect of supplementing 30 g N-hydroxymethyl-DL-methionine-calcium (HMM-Ca) from 14 days pre calving till 100 days in lactation on the performance and some physiological traits. Cows were kept on four energy levels by feeding different amounts of concentrate. At each energy level, half of the cows were given a methionine supplement. Forage consisted of 1/3 corn- and/or beet pulp silage and 2/3 grass silage ad libitum. The amount of daily milk yield differed not significantly from 31.5 kg for the supplement group to 30.6 kg for the control group. No interaction between the methionine supplementation and energy level could be detected. Mean methionine content in blood plasma differed from 22.7 mmol/l for the supplement group to 16.8 mmol/l for the control group. GOT, tau-GT, bilirubin and urea in blood serum and milk urea content did not indicate a positive effect of the methionine supplementation on the metabolism. Conception rate differed slightly from 87% in the supplement group to 73% in the control group.