BREED AND AGE OF DAM INFLUENCES ON BEEF SIRE EVALUATIONS FOR EASE OF CALVING

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Abstract
Canadian Record of Performance for Beef National Sire Monitoring Program ease of calving records for the years 1975–1978, inclusive, for Charolais (1232 sires, 20 256 calves) and Simmental (944 sires, 68 943 calves) were used to compare BLUP sire proofs calculated from records from different dam populations. Product-moment correlations between sire proofs from all data and only 2-yr-old dam data were 0.61 for Charolais and 0.56 for Simmental. Correlations between proofs from all data and from records from individual dam breeds were 0.87, 0.61, and 0.38 for Charolais sires when mated to Charolais, 50% and 75% Charolais, or British (Angus, Hereford or Shorthorn and their crosses) dams, respectively, and 0.15, 0.45, 0.51, 0.70, and 0.43 for Simmental sires when mated to Angus, Hereford, 75% Simmental, Simmental × British, or British cross dams, respectively. Correlations were not statistically different from the expected values except in one case. There was no evidence in this study indicating a need for separate sire proofs for ease of calving for either 2-yr-old mates or mates of individual breeds or crosses.