Modelling reproductive management systems for beef cattle

Management alternatives for beef herds that varied in level of reproductive efficiency were studied by computer modelling. This paper describes the stochastic dynamic model developed to describe reproductive processes in beef cattle. The model is compared with other stochastic models of reproduction in cattle. Results from modelling different management alternatives (length of breeding season and breeding heifers 21 days ahead of cows in spring-calving herds) are discussed. Proportion of females in the breeding herd that became pregnant increased with length of breeding season and by breeding heifers ahead of cows. Proportion of females in the breeding herd that weaned a calf was mostly affected by the pregnancy rate but also by survival of calves to weaning. Average age of calves at weaning increased with increasing first-service conception rate and decreased length of breeding season. With high first-service conception rate, length of breeding season had relatively little effect on age and weight at weaning.