For most beef cow herds, the single most important means of increasing income is increasing the number of calves weaned and sold relative to the number of cows in the operation, or by definition, increasing reproductive efficiency. While certain production and carcass traits can be most directly influenced by genetic selection, reproductive performance is overwhelmingly influenced by management. Increasing the profitability of a ranch operation therefore relies very heavily on adjusting management practices to improve reproductive efficiency. In order to accomplish this, we first need to know what factors are most influential in reproductive performance. We specifically need to identify those factors that can be improved by changes in manag...