Submitted to: Encyclopedia of Animal Science
Publication Type: Book / Chapter
Publication Acceptance Date: 10/16/2003
Publication Date: 12/23/2004
Citation: Norman, H.D., Hubbard, S.M. 2004. Dairy cattle: breeding and genetics. Encyclopedia of Animal Science. 1(1):264-267. Pond, W.G., and Bell, A.W. (ed.). Marcel Dekker, Inc., Academic Press, New York, NY.
Technical Abstract: Five factors are primarily responsible for the exceptional genetic improvement achieved by domestic dairy cattle: 1) permanent unique identification, 2) parentage recording, 3) recording of milk yield and other traits of economic importance, 4) artificial insemination, and 5) statistically advanced genetic evaluation systems. The success of practical application of genetic improvement procedures is evident in the U.S. dairy population: as cow numbers have decreased, yield per cow has increased, in part because of improved genetic capacity for efficient dairy production as indicated by similar trend in the genetic merit of dairy bulls and cows. Because of the increased efficiency achieved through genetic programs, competition for sales of genetic material has increased. The higher productivity of North American breeds, particularly Holstein, in the 1980s has led to semen exports of more than $50 million per year. Increasing global trade in semen, embryos, and livestock resulted in a need for accurate comparisons of animal performance both within and across countries. Currently, the International Bull Evaluation Service provides evaluations for bulls from over 27 populations (breed within country) for milk, fat, and protein yields; 18 populations for 18 conformation traits; and 12 populations for udder health traits. Nearly all dairy countries that calculate genetic evaluations for different traits produce an overall economic index in which the traits are combined according to their economic value. The worldwide improvement in production efficiency over the past 100 years allows dairy products to be produced with fewer cattle, thereby reducing adverse environmental impacts and conserving natural resources. The increased genetic merit of dairy populations has resulted in a global marketplace for germplasm and live animals.