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Simultaneous Selection for Milk an Beef Production Among Holstein-Friesians

Department of Animal Science, Cornell University, Ithaca, New York 14850

ABSTRACT

A selection index combining milk and beef production traits, such that progress in aggregate economic value is maximized, was constructed for Holstein bulls. The index for milk was I_M = 1.11X₁ + .997X₂ while the index for beef trait was I_B = .008X₁ + .619X₂ where X₁ is the daughters' average lactation yield (kg) and X₂, bulls' body weight at 15 mo (kg).

The relative genetic progress from simultaneous selection for milk and beef traits with different emphasis was estimated. Expected genetic progress in beef production (body weight at 15 mo) declined with increasing selection on milk and vice versa. Expected genetic progress, however, did not fall below one-third of maximum genetic progress (100%) for either milk or beef, regardless of the emphasis of selection.

Based on current milk and beef values, ignoring milk and selecting solely for beef would give the highest genetic progress in total economic value but quite slow genetic progress in total protein production. Ignoring beef and selecting solely for milk would give the highest genetic progress in total protein production and a fairly high genetic progress in total economic value. A 1:7 beef to milk emphasis per standard deviation seems to be most appropriate since it results in large genetic progress in both total protein and total economic value.

¹ Present address: East-West Food Institute, Honolulu, Hawaii 96822.

² Present address: American Breeders Service, Inc., De Forest, Wisconsin 53532.