Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2011
Publication Date: 12/1/2011
Citation: Norman, H.D., Hutchison, J.L., Van Raden, P.M. 2011. Evaluations for service-sire conception rate for heifer and cow inseminations with conventional and sexed semen. Journal of Dairy Science. 94(12):6135-6142.
Interpretive Summary: Evaluations for Holstein and Jersey service-sire conception rate (SCR) were calculated based on cow or heifer inseminations with conventional or sexed semen. Little relationship was found between conventional and sexed semen SCR based on either cow or heifer inseminations. However, cow and heifer SCR were highly related when SCR was based on either conventional or sexed semen. Service-sire conception rates appeared to be more accurate across time when cow and heifer inseminations were combined. Separate SCR evaluations are needed for conventional and sexed semen.
Technical Abstract: Service-sire conception rate (SCR), a phenotypic fertility evaluation based on conventional (nonsexed) inseminations from parities 1 through 5, was implemented by USDA in August 2008. Using insemination data from 2005 through 2009, the SCR procedure was applied separately for nulliparous heifer inseminations with conventional semen (SCRHconv), nulliparous heifer inseminations with sexed semen (SCRHsexed), cow inseminations with conventional semen (SCRCconv), and cow inseminations with sexed semen (SCRCsexed). Holstein and Jersey bulls with =300 and =200 artificial inseminations, respectively, in =10 herds and with =100 breedings during the 12 mo prior to evaluation were included. Numbers of bulls evaluated for SCR in January 2010 were 270 Holsteins and 16 Jerseys for SCRHconv, 114 Holsteins and 6 Jerseys for SCRHsexed, 2,309 Holsteins and 214 Jerseys for SCRCconv, and 25 Holsteins and 7 Jerseys for SCRCsexed. Fixed age effects for service sire were consolidated in sexed-semen models because of the limited number of bulls. Mean Holstein reliabilities were 82% for SCRHconv, 75% for SCRHsexed, 79% for SCRCconv, and 73% for SCRCsexed. Mean SCR for each evaluation category was set to 0; Holstein standard deviations were 2.55% for SCRHconv, 4.29% for SCRHsexed, 2.21% for SCRCconv, and 2.39% for SCRCsexed. Correlations between Holstein SCRHconv and SCRHsexed were -0.21 for August 2009 and 0.08 for January 2010; predicted correlations between true SCR were -0.27 and 0.11. Correlations between Holstein SCRCconv and SCRCsexed were 0.10 for August 2009 and 0.18 for January 2010; predicted correlations for true SCR were 0.14 and 0.24. Bull ranking for fertility with sexed semen differs markedly from those with conventional semen. In contrast, correlations between Holstein SCRHconv and SCRCconv were 0.68 for August 2009 and 0.67 for January 2010, with predicted true SCR correlations of 0.85 and 0.82; corresponding correlations between Holstein SCRHsexed and SCRCsexed were 0.73 and 0.76, with predicted true correlations of 1.00 and 1.03. Results for Jerseys were similar. Rankings for SCR could benefit from combining cow and heifer data but should be kept separate for conventional and sexed semen inseminations.