Milk Production and Nitrogen Utilization by Dairy Cows Infused Postruminally with Sodium Caseinate, Soybean Meal, or Cottonseed Meal

Abstract
Four Holstein cows with fistulated rumens were in a 4 .times. 4 Latin square design for us to determine effects of administering different sources of protein postruminally on milk production, milk composition and efficiency of nitrogen utilization. Treatments consisted of postruminal infusion of water, sodium caseinate, soybean meal or cottonseed meal. Milk yield (kg/day) and milk protein production (g/day) for the 4 treatments were:1) 30.6, 1043; 2) 32.7, 1146; 3) 32.1, 1102 and 4) 31.1, 1087. Synthesis of milk protein increased during postruminal infusions of protein as indicated by the increased casein nitrogen fraction in milk. All protein infusions improved efficiency of use of absorbed nitrogen for synthesis of milk protein. Milk fat percentage and daily production of milk fat were not affected by treatments.