FACTORS INFLUENCING CALVING PERFORMANCE IN RANGE BEEF CATTLE

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Abstract
Data from 2964 calving records of cows of all age groups and 1035 calving records of 2-yr-old heifers from three breeding groups (B), Hereford (HE), Beef Synthetic (SY) and Crossbred (XB) maintained at the University of Alberta Ranch at Kinsella were analyzed by the least squares method. Dam weight at calving (DAMWT), age of dam (A), calf birth weight CBWT, sire and dam birth weights and the interactions between A and CBWT, B and A, sex (S) and A and finally B and CBWT had significant influences on calving performance when calving records of all age groups were considered. Among heifers the effects of DAMWT, CBWT, B, S, dam birth weight and interaction between B and DAMWT were significant. DAMWT and CBWT were among the most important factors influencing calving performance. CBWT had a major influence in 2-yr-old dams with no noticeable influence in other age groups. Calving performance score of HE heifers was lower than those from XB and SY heifers, but breed group differences were minor at other age groups. Similarly males had more difficult births than female calves from young dams with no detectable sex influence from older dams. DAMWT had a greater positive impact on calving performance of HE heifers compared with the other two breeding groups. These interactions emphasize the importance of interrelationships of major factors influencing the incidence of dystocia in beef cattle. Key words: Factors, calving difficulty, beef cattle