Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: 11/27/2009
Publication Date: 11/27/2009
Citation: Van Raden, P.M., Cole, J.B., Tooker, M.E., Cooper, T.A. 2009. Genetic Base Changes for January 2010. AIPL Research Reports. BASE2 (8-09).
Interpretive Summary: Genetic evaluations of dairy cattle are expressed relative to a base population that is held constant for 5 years so that estimates of genetic merit from new and previous evaluations are easy to compare, and then the base is updated. In January 2010, the genetic base for USDA-DHIA genetic evaluations of yield, health, fertility, and type traits will become the average value for cows born in the year 2005. In general, positive progress has been made for most traits through management practices and genetics since the 2005 base change. The new base changes make identifying and comparing genetically superior animals easier. By selecting genetically superior animals, dairy producers will increase profitability.
Technical Abstract: Genetic bases were updated previously in the United States in 1965, 1974, 1984, 1989, 1995, 2000, and 2005, and the next base change is scheduled for January 2010. Changing the base every 5 years subtracts accumulated genetic gain so that all animals are compared with a more recent cow population, while allowing new and previous evaluations to be compared easily for the 5 years between changes. In January 2010, the genetic base for USDA-DHIA genetic evaluations of yield, health, fertility, and type traits will become the average value for cows born in the year 2005. As a result of updating the base year, evaluation standard deviation for each breed will be adjusted along with the average. For most traits, phenotypic and genetic trends comparing cows born in 2005 with those born in 2000 were equal to or slightly less than corresponding trends for the preceding 5 years reported in February 2005. For Holsteins, genetic improvement was responsible for 90% of the increase in protein yield, 94% of the increase in fat yield, and 107% of the increase in milk yield during the past 5 years; the negative effect of environmental factors on milk yield caused the phenotypic change to be less than the genetic change. Phenotypic progress in yield traits for other breeds also was predominantly the result of genetic improvement. In general, positive progress has been made for most traits through management practices and genetics since the 2005 base change.