Using Genomics to Improve the Genetic Potential and Management of Your Herd

For more than half a century, progeny testing has been the foundation of genetic selection programs in dairy cattle (Robertson and Rendel, 1950). Several factors make progeny testing especially advantageous in dairy cattle, most notably widespread use of artificial insemination (AI) with frozen semen and the fact that nearly all traits of economic importance, including milk production, milk composition, female fertility, length of productive life, calving ability, disease resistance, and physical conformation, are sex-limited and cannot be measured until females begin lactating. Progeny testing has led to rapid genetic gains in production traits; estimated breeding values (EBV) of North American Holsteins have increased by roughly 90 kg of milk, 3 kg of fat, and 3 kg of protein per year over the past decade. However, genetic progress is limited by long generation intervals of approximately 7.1 and 3.9 years, respectively, for sires and dams of AI bulls (Normal et al., 2001). Furthermore, progeny testing is not a cost-effective method for improving traits that are difficult or expensive to measure routinely on commercial dairy farms, such as feed efficiency.