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Correction Factors and Germ Plasm in Dairy Cattle Breeding

University of Illinois

Abstract

The benefit of correction factors applied to milk yields, as giving a better estimate of germ plasm or genetic make-up of the cow, is very dubious, judged by certain herd test records of the Holstein-Friesian Association. The correlation between various records of the same cow is lower for the official corrected records than for the official actual records. As between individual sire daughter groups (the field within which the dairyman must work) the actual correlations range from r = + .982 ± .007 to r = – .60 ± .15, with an average value of about + .3. A plain lesson is the necessity of continuous or lifetime records under a plan that avoids correction factors.

A plan is recommended, in its own right and to dispose of the correction problem. It is based on the herd test system with the addition of live weight of the cow, and considers the first 8 months of each lactation on the basis of milk energy per unit initial live weight. The plan regards the cow as a machine to convert feed energy into milk energy and considers 3 mutually independent values: 1. Live weight, or size of machine. 2. Calories per kilogram per day, or working efficiency of machine. 3. Fat percentage, or kind of work of machine.