Effects of Supplemental Ruminally Protected Forms of Methionine on Holstein Dairy Cows Fed Imported Roughage

Abstract

The objective of this experiment was to determine whether ruminally protected forms of methionine (RPMet) increase lactational performance of cows fed imported roughage. Supplements of either 0 or 20 g/day of RPMet were administered to 18 Holstein cows (16 multiparous and 2 primoparous) from late pregnancy (-20 days) to the end of lactation. According to the Cornell Net Carbohydrate and Protein System (CNCPS), the lactation diet 40 kg/day milk yield were limited for Met, Leu, and His. In terms of fat-protein-corrected milk and milk protein, percentages of milk protein and solid not fat (SNF) increased significantly when RPMet was administered. Except for total cholesterol (TCho) and apolipoprotein B-100 (apo B-100) serum concentrations, health and reproduction measurements were similar in both groups of cows. RPMet increased serum concentrations of Met, total amino acids, and total nonessential amino acids. The results of this study suggest that supplenments of RPMet to a diet based on imported roughage administered during the early lactating phase overcome amino-acid limitations and increase milk production, thereby improving lactational performance.