Impact of genomic selection of AI dairy sires on their likely utilization and methods to estimate fertility A paradigm shift》.pdf

Available online at Theriogenology 77 (2012) 795–817 Review Impact of genomic selection of AI dairy sires on their likely utilization and methods to estimate fertility: A paradigm shift R.P. Amanna,*, J.M. DeJarnetteb a Animal Reproduction and Biotechnology Laboratory, Colorado State University, Ft. Collins, Colorado, USA b Select Sires, Inc., Plain City, Ohio, USA Receivied 1 June 2011; received in revised form 25 August 2011; accepted 3 September 2011 Abstract Breeding of dairy cattle is undergoing a paradigm shift to genomic selection of potential sires and dams. This undoubtedly will affect how bulls are managed in an artificial insemination (AI) center and impact methods to estimate their ‘fertility’. Our goal is to help decision-makers understand the contents of a straw of semen, current estimates of sire fertility, and how estimates might evolve in a genomic era. Sire fertility is estimated from outcome (pregnant or not) after 300 to 2,000 inseminations and reported in units (U) as a sire’s deviation from a population ( 500 bulls) average pregnancy rate (PR). Too often users do not recognize that imprecision of an estimate encompasses a 3-U range, or more. ‘True fertility’ of the sire whose semen is inseminated influences outcome far less than ‘true fertility’ of each female and a myriad of microenvironment and management factors. Further, AI centers discard substandard collections and intentionally adjust number of sperm per straw so that differen