Lactation Studies. IX. Relationship of Milk Flow Rate and Complementary Milk to Milk Yields in a Herd of Holstein Cattle1,2,5

Abstract

Maximum rate of milking, percentage of complementary milk, and milk production were compared monthly and over complete lactations for 81 cows from the Minnesota Valley Breeders Association. The cows were arranged into 21 sire groups, to estimate variability attributable to sires for rate of milking, percentage of complementary milk, and milk production.Rate of milking measurements were obtained from a milking profile as recorded by a continuous feed kymograph. Immediately after milking, 10 IU oxytocin were injected intravenously and complementary milk obtained by hand-milking.As shown by correlation and regression analysis, both variables were related to total lactation milk production. Rate of milking and percentage of complementary milk combined explained 10% of the total variation in lactation milk production. Percentage of complementary milk explained a greater part of the variation in lactation milk production than rate of milking. This experiment tends to show that faster-milking cows have less complementary milk (more persistent) and, consequently, have higher lactation production.