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Genetic Principles Governing the Rate of Progress of Livestock Breeding

University of Chicago

Abstract

I should say first that the most important limitations on progress in livestock breeding are not strictly genetic. There can be little progress unless there is agreement among breeders on a clearly defined objective. Clarity can only be obtained if judgment can be replaced by measurement. This can be done fairly easily in some cases, e.g. milk and egg production—much less easily in others e.g., meat production. Allied to this is the desideratum of a simple objective. It is difficult enough to change one thing at a time. The difficulty is enormously increased if it is attempted with two or more characters. Yet the aim can never be as simple as in a laboratory experiment. The breeder must, for example, take into account not merely production, but economy of production in his conception of the character to be improved. Moreover he must at least hold his own with respect to general vigor and fertility while attempting to improve other characters, if success after years of effort is not to be foliowed shortly by dwindling numbers and ultimate extinction of the improved strain.