Genetic Progress

Practical success of genetic improvement procedures is evident in the U.S. dairy population. As cow numbers decreased, yield per cow increased (Fig. 1), in part because of improved genetic capacity for efficient dairy production, as indicated by similar trends in the genetic merit of dairy bulls and cows (Fig. 2).

Because of increased efficiency achieved through genetic programs, competition for sales of genetic material has increased. Higher productivity of North American breeds, particularly Holstein, in the 1980s[5] has led to U.S. semen exports of more than $50 million per year. As a result, the international dairy population is much more related, and population sizes of many local breeds were reduced, in a few cases to the point of extinction. As selection methods intensified, concern about level of inbreeding has increased, and interest in crossbreeding has been growing to alleviate this concern and to capture the known benefits of heterosis.

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