IMPACT OF BULLS RECOMMENDED FOR CALVING EASE ON CALVING TRAITS AND MEAT PERFORMANCE

Calving performance, gestation length, birth weight and body measureme nts were taken on German Simmental heifers and cows and on their calve s sired by easy-calving-AI-bulls (ECB). Fattening and carcass performa nce 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 L SQ-estimate for calves of normal-calving-AI-bulls (NCB). Gestation len gth was 1.2 days shorter for the ECB-progeny. Calves sired by ECB had significantly smaller shoulder width and the LSQ-estimates for chest c ircumference, head- and pelvic-width were lower than those of the NCB- progeny. The calving performance was analysed on the original scale (f ive 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 ana lyses were similar. Considering the whole calving performance data of heifers and cows the calvings with ECB-sire tended to be earlier. Sepa rate analysis of the calving performance of cows showed significantly easier calvings for calves with an ECB-sire. Due to a high rate of nat ural service in heifers. the results of the separate analysis of recor ded heifer calvings showed no significant effect of ECB. No significan t effects of ECB were found for fattening and carcass performance. Sin ce birth weight of ECB-calves was significantly lower, this might be c aused by compensatory growth. To clarify presumption, further analysis with a bigger and better structured dataset is necessary.