Economic Weights for Genetic Changes in Milk Component Yields at the Herd Level

¹ Department of Dairy Science, The Ohio State University, Columbus 43210

Economic weights for separate 1-kg increases in herd average genetic levels for fat, protein, carrier, and lactose yields were calculated for five daily breeds and three alternative milk markets. Economic weights were calculated using a dairy herd production model that predicted costs and returns of production from expected phenotypic levels accounting for genetic potential, age effects, and the herd age distribution. The model accommodated genetic differences in mature milk component yields and body weight. Herd age distribution variables (calving interval, age at first calving, and culling rate) had only a scale effect on economic weights, affecting all components similarly by changing the amount of actual milk predicted from a given average genetic potential. Comparisons showed that a profit (returns minus costs) basis inflates economic weights compared to an economic efficiency (returns divided by costs) basis. Economic efficiency economic weights for protein, carrier, and lactose expressed relative to the weight for fat were –.10, .02, and –.08 in a fluid milk market and 1.06, –.02, and –.13 in a multiple component market, respectively, averaged across all breeds. In a cheese yield market, similar values for carrier and lactose were found, but protein values were .9 and 1.4 for the three lower solids breeds and the two higher solids breeds, respectively. Changing levels of feed costs or costs other than feed had linear effects on profit economic weights but nonlinear effects on economic efficiency weights.

Key Words: economic weights • dairyherd production model • milk component yields

Submitted on October 12, 1989
Accepted on January 23, 1990