Blood and Hydrolyzed Feather Meals as Sources of Undegradable Protein in High Fat Diets for Cows in Early Lactation

Abstract

Thirty-six cows were in a 2 × 3 factorial study during the first 2 mo of lactation to examine effects on milk yield and composition of added fat (5% of feed DM) and percentage of ruminally undegradable protein (100, 120, or 140% of recommended intake) in the diet. The main source of added undegradable protein was a 1:1 (wt/wt) mixture of blood meal:hydrolyzed feather meal. Diets were low in ADF (ca 14%) and were highly fermentable in the rumen. The amount of intermediate dietary protein reduced feed intake. Milk yield was high (40 to 44 kg/d), similar among treatment groups, and was sustained for the entire 60-d trial. All cows yielded milk of low fat content (2.1 to 3.2%); supplemental fat decreased proportions of C6 to C14, C18:2. and C18:3 in milk fat and increased C4, C16:0, C18:0, and C18:1. Higher dietary protein had a positive linear effect on milk fat percentage and increased C16:O and decreased trans-C18:1 and C18:2 contents of milk fat. Added fat did not change total milk N but increased NPN as a percentage of total milk N. Percentage of total N in milk and yield of whey N was reduced when the intermediate protein diet was fed, associated with the lower DMI of this diet. A requirement for ruminally undegradable protein intake higher than recommended by NRC was not demonstrated with the highly fermentable diets fed in this study; however, ruminal acetate: propionate ratio and milk fat percentage were low.