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Selection of Dairy Cattle for Overall Excellence¹

Dairy Science, Michigan State University, East Lansing 48824

ABSTRACT

Methods from plant breeding were adapted to develop economic weights for milk production, mastitis, milk fat test, live freshenings, herd life, body weight, and milking time from individual lifetime data on 111 cows. Standard partial regression coefficients of profit per year of herd life which varied from $409 to –$658 (mean $59) on these traits were .64, –.38, .31, .22, .10, .09, and .03. A prediction equation using derived economic weights ranked cows in substantial agreement with actual profit. All seven traits of the original index accounted for 68% of variation in profit, four economically significant traits, reduced index, 66%, and three traits with their heritabilities, final index, 56%. Substitution of mature equivalent for actual milk production reduced variation explained to 53, 50, and 43%. Original, reduced, and final indexes predicted profit more accurately than actual or mature equivalent milk production. The method enables practical field indexes and useful economic weights.

¹ Michigan Agricultural Experiment Station Journal Article 6874. Part of North Central Region Project NC-2.

² American Breeders Service, De Forest, WI 53532.