the effect of using rumen protected methionine (mepron) on production and reproduction performance of holstein lactating cows during early lactation under field condition

in order to examine the effect of using rumen protected methionine (mepron, evonik industries, hanau, germany) on productive and reproductive performance under field condition, 195 holstein cows were used in a unbalanced completely randomized design and 2 groups. experimental treatments consisted of: 1) control group with 110 holstein dairy cows (71±51 dim and 47.5±12 milk yield) and without mepron and 2) experimental group with 85 holstein dairy cows (85±59 dim and 47.0±12 milk yield) and 13 g mepron per cow/d. cows were group fed with tmr and 4 times a day. the diets were balanced with aminocow® software. using mepron decreased cp content from 17.05% in control group to 16.47% in experimental group, while other nutrients were similar between two diets. adding mepron to diet resulted in a significant increase in dry matter intake (p<0.01; 25.8 vs. 26.6 kg/d) and a decrease in daily feed cost per cow (70820 vs. 69180 rials). milk yield and lactose percentage did not affect but a tendency was detected for more protein percentage (p<0.13; 3.02 vs. 3.10) and lower fat percentage (3.15 vs. 3.08) in experimental group. decrease in milk urea nitrogen (mun) in experimental group compared with control tended to be significant (p<0.17; 18.8 vs. 17.6 mg/dl). pregnancy rate increased 13% in experimental group compared with control group (41.8 vs. 45.9%). these results show positive effects of feeding rumen protected methionine under field condition on improving productive and reproductive performance.