Technical note: Changes to herd cutoff date in conception rate evaluations

Service-sire conception rate (SCR) evaluations were implemented for the United States in August 2008. Only inseminations from the most recent 4 yr of breeding records are used for SCR evaluations, and all inseminations must have occurred ≥ 70 d before the data submission deadline for an evaluation. In April 2012, edits for SCR were modified so that all inseminations must have occurred ≥ 70 d before the last herd test date rather than the constant date of 70 d before the data submission deadline. This edit more precisely measures the days of opportunity for a cow to be diagnosed as pregnant or not pregnant following insemination, and is herd specific. The number of inseminations before the edit change was 16,906,385 compared with 16,492,331 after the edit change. Correlations of SCR before and after the edit change were 0.96 for Holsteins and slightly lower for other breeds, with little change in mean or standard deviation. Weekly mean conception rates after the edit change were more stable for the most recent inseminations. The conception rate was 60% at wk 10 before the constant cutoff date (before edit change) compared with 42% at 10 wk before the last herd test date (after the edit change). Similar edits to SCR are applied to heifer conception rate (HCR) and cow conception rate data (CCR), and were changed in August 2012 to use herd-specific cutoff dates. The HCR and CCR correlations before and after the edit change were 0.99 or higher for all breeds, with little change in mean or standard deviation. The new edits improve accuracy of SCR, HCR, and CCR evaluations by accounting for differing opportunity to confirm pregnancy caused by discontinued testing or differences in herd testing schedules.