Impact of bulls recommended for calving ease on calving traits and meat performance

Calving performance, gestation length, birth weight and body measurements were taken on German Simmental heifers and cows and on their calves sired by easy-calving-AI-bulls (ECB). Fattening and carcass performance traits of male progeny from these matings were recorded. The birth weight of calves with an ECB-sire was 2.0 kilogrammes less than the LSQ-estimate for calves of normal-calving-AI-bulls (NCB). Gestation length was 1.2 days shorter for the ECB-progeny. Calves sired by ECB had significantly smaller shoulder width and the LSQ-estimates for chest circumference, head- and pelvic-width were lower than those of the NCB-progeny. The calving performance was analysed on the original scale (five categories) and as a transformed trait. In the transformation each observation was replaced by the average value of the category on the scale of an underlying normal distribution. The results of the two analyses were similar. Considering the whole calving performance data of heifers and cows the calvings with ECB-sire tended to be earlier. Separate analysis of the calving performance of cows showed significantly easier calvings for calves with an ECB-sire. Due to a high rate of natural service in heifers. the results of the separate analysis of recorded heifer calvings showed no significant effect of ECB. No significant effects of ECB were found for fattening and carcass performance. Since birth weight of ECB-calves was significantly lower, this might be caused by compensatory growth. To clarify presumption, further analysis with a bigger and better structured dataset is necessary.