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Lactation Studies. IX. Relationship of Milk Flow Rate and Complementary Milk to Milk Yields in a Herd of Holstein Cattle^{1, 2, 5,}

Department of Dairy Husbandry, University of Minnesota, St. Paul

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.

¹ Scientific Journal Series Paper no. 5709, Minnesota Agricultural Experimental Station.

² Data presented are based on a thesis by A. H. J. Rajamannan in partial fulfillment of the requirements for a Master of Science degree.

⁵ Supported in part by National Institute of Health Grants FR-00011 and GM 67804.

³ Present address: Consolidated Breeders Association, Anoka, Minnesota.

⁴ Present address: Department of Experimental Statistics, North Carolina State University at Raleigh, Raleigh, North Carolina.