The profitability of suckled calf production is closely linked to the number and value of calves weaned. Hence, herd fertility is a crucial measure of efficiency. For the commercial suckled calf producer fertility can be defined as the production of a viable, quality calf when required. While there are many factors influencing herd/individual conception rates, three of the most important are time, nutrition and calving difficulties.

Conception rates to first oestrus post-partum are low, particularly where post-partum anoestrus periods are short. This effect can be clearly seen in trials monitoring over 1500 suckler cows where fertility was depressed if the interval between calving and mating was less than 30 days, ie the calving period extended over 50 days. Where however the post-partum anoestrus period is extended the depression in conception rate to first oestrus is less marked.