ESTIMATION OF GENETIC TRENDS FOR CANADIAN STATION-TESTED BEEF BULLS

Abstract

Data collected from Canadian central test stations were used to obtain estimates of genetic progress for test station average daily gain (ADG-T), height at hooks (HH), ultrasonically measured backfat thickness midway between the 11th and 12th ribs (FAT) and scrotal circumference (SC). Where possible, records for preweaning average daily gain (ADG-W) from the Federal-Provincial Herd Record of Performance program were obtained for tested bulls. Estimated breeding values were regressed on year of birth to obtain estimates of genetic trend for each trait, for the six principal breeds enrolled in the testing program: Aberdeen Angus (AA), Charolais (CH), Hereford (HE), Limousin (LM), Shorthorn (SH) and Simmental (SM). Estimated trends were generally significant with the exception of those for the LM breed, and the trait of SC. For FAT, trends were generally positive for the exotic breeds, and negative for the British breeds. Significant positive trends were observed for HH, ADG-W and ADG-T for most breeds. Examples of estimated genetic trends, for the HE breed, were 0.0022 kg d−1 yr−1, 0.0023 kg d−1 yr−1, 0.090 cm yr−1 (NS), − 0.029 mm yr−1, and 0.009 cm yr−1 (NS), respectively, for ADG-W, ADG-T, HH, FAT and SC (NS = not significant). Most estimated trends were low, in the order of 0.1 to 0.5% of population mean per year. Key words: Genetic trend, central test stations, beef bulls