Protected methionine supplementation to a barley-based diet for cows during early lactation.

Formulation of diets using barley and soybean meal should result in a diet that supplies less methionine than conventional corn and soybean meal diets. To evaluate this further, 28 high producing Holstein cows (10 primiparous and 18 multiparous) were fed a barley soybean meal diet without or with 15 g of added DL-methionine as 50 g of ruminally protected methionine product during wk 4 to 16 postpartum. Cows were fed a 15% CP total mixed diet consisting of (dry matter basis) 50% concentrate mix, 45% corn silage, and 5% chopped alfalfa hay. Yields of milk (30.3 and 29.8 kg/d), 4% fat-corrected milk (26.0 and 25.6 kg/d), and solids-corrected milk (26.3 and 25.9 kg/d) were similar for cows fed diets without or with added methionine. Percent of milk fat (3.08 and 3.16%) and solids-not-fat (8.66 and 8.71%) were similar, but percent protein (2.75 and 2.87%) was higher, from cows fed ruminally protected methionine. Methionine concentrations in arterial and venous serum were not significantly elevated by feeding ruminally protected methionine. Supplemental ruminally protected methionine did not increase milk production but did increase milk protein percentages in cows fed barley-based diets.