Selection Changes in the United States Due to Genomics

Abstract

Recent changes in U.S. breeding programs that resulted from the implementation of genomic evaluation were documented. In 2013, over 146 000 females and 20 000 males were genotyped in the United States. Mean number of U.S. bulls that entered artificial insemination (AI) service from 2008 to 2013 was 2 033. From 2010 to 2013, mean age of sires when AI bulls were born decreased from 7.2 to 3.6 years, and mean age of dams decreased from 3.9 to 3.2 years. Reductions for mean ages of paternal and maternal grandparents were similar to those reflected in (respective) parents; largest decreases were for paternal grandsires (from 14.0 to 9.6 years) and for paternal granddams (from 11.6 to 7.3 years). For bulls that entered AI service over the same 5 years, the percentage that resulted from embryo transfer increased from 76 to 89. For bulls entering AI from 2008 to 2013, genetic gains for milk, fat, and protein yields and the three lifetime merit indexes were around twice the gains for bulls entering AI from 2005 to 2008; comparable later genetic gain difference for productive life was slightly higher. For potential future genetic changes based on breeding records, comparable gains were 50% for milk yield and 60% for fat and protein yields. The use of genomic predictions has accelerated genetic improvement for most currently evaluated traits.