Balancing for Amino Acids in Dairy Diets

Abstract

The objectives of this study were 1) to test the ability of the amino acid submodel of the CNCPS to predict amino acid flow at the duodenum, and 2) to determine if early lactation cows would respond to rumen bypass amino acids with an increase in milk or milk protein yield. Five early-lactation Holstein cows were fitted with rumen and duodenal cannulae and utilized in a metabolism trial with a 5 x 5 Latin square design. Two diets were formulated to contain equal amounts of crude protein, degradable and undegradable protein (UIP), neutral detergent fiber, and non-structural carbohydrate. These diets used either fish meal or corn gluten meal and corn distiller's grain as sources of UIP. Bypass lysine (23 g/day) or bypass methionine (13 g/day) or both were then added to the corn protein-based diet. Diets consisted of grass silage, a barley and corn-based concentrate with the appropriate protein supplement, and whole cottonseed.