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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #311088
Title: Genetic base changes for December 2014

Author
item Vanraden, Paul
item Tooker, Melvin
item Wright, Janice
item Cole, John
item Null, Daniel
item LAWLOR, THOMAS - Holstein Association Usa, Inc

Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: 10/3/2014
Publication Date: 10/3/2014
Citation: Van Raden, P.M., Tooker, M.E., Wright, J.R., Cole, J.B., Null, D.J., Lawlor, T.J. 2014. Genetic base changes for December 2014. AIP Research Report BASE3(10-14).

Interpretive Summary: Genetic bases were updated previously in the United States in 1965, 1974, 1984, 1989, 1995, 2000, 2005, and 2010, and the next base change is scheduled for December 2014. Base changes for yield, health, fertility, and type traits in December 2014 are reported. Stepwise genetic bases allow estimates of genetic merit from new evaluations to be easily compared with previous estimates except at base changes, when accumulated genetic gain is subtracted so that all animals are compared with a more recent cow population. A particular animal's genetic evaluation is supposed to decrease when the base is changed and remain fairly constant between base changes. For most traits, genetic and phenotypic trends comparing cows born in 2010 with cows born in 2005 are equal to or slightly less than trends for the preceding 5 years reported at the previous base change in January 2010. However, cows born in 2010 were before genomic selection had much impact, and trends are faster for calves born during the last 4 years. Phenotypic progress due to environmental factors such as management is the difference between genotypic and total phenotypic progress. For Holsteins, genetic improvement is responsible for 86% of the increase in protein yield, 87% of the increase in fat yield, and 132% 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.

Technical Abstract: Genetic bases were updated previously in the United States in 1965, 1974, 1984, 1989, 1995, 2000, 2005, and 2010, and the next base change is scheduled for December 2014. Base changes for yield, health, fertility, and type traits in December 2014 are reported. Stepwise genetic bases allow predicted transmitting abilities (PTAs) from new evaluations to be easily compared with previous evaluations except at base changes, when accumulated genetic gain is subtracted so that all animals are compared with a more recent cow population. A particular animal's PTA is supposed to decrease when the base is changed and remain fairly constant between base changes. For most traits, genetic (PTAs) and phenotypic (standardized first-lactation traits) trends comparing cows born in 2010 with cows born in 2005 are equal to or slightly less than trends for the preceding 5 years reported at the previous base change in January 2010. However, cows born in 2010 were before genomic selection had much impact, and trends are faster for calves born during the last 4 years. As a result of updating the base year, the standard deviation (SD) of PTA for each breed is adjusted along with the mean. Yield and somatic cell score records are adjusted for variance within herd and year to have the same SD as the base year using an SD ratio based on calving year. Phenotypic progress due to environmental factors such as management is the difference between genotypic and total phenotypic progress. For Holsteins, genetic improvement is responsible for 86% of the increase in protein yield, 87% of the increase in fat yield, and 132% 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.