Milk Production Response to Nitrogen Solubility in Dairy Rations

Abstract

Holstein cows (20), in their 8th-10th wk of lactation, were assigned randomly to 4 equal groups in a 2 .times. 2 factorial 9 wk experiment to determine the effect of N solubility on protein utilization. Percents of protein (13 and 15%) and 2 nitrogen solubilities (22 and 42%) were obtained by selecting from natural feedstuffs. Four complete rations (concentrate plus sorghum silage) were fed ad lib. Soluble N did not affect average daily intakes of dry matter, crude protein, or net energy-lactation. The higher protein increased these average daily intakes. The lower N solubility increased milk yield. No significant effects were detected in total milk solids, milk fat, milk protein and milk solids-not-fat percentages.