Abstract

One important attribute of a beef-breeding cow is the ability to wean a calf every year. Furthermore, an earlierborn calf is likely to be heavier at weaning and its dam has more opportunity to conceive again during the following breeding season. In a spring-calving system under the seasonal pastoral-grazing system in New Zealand, a 365- day intercalving interval is desirable. A normal gestation length is 280 days leaving 85 days for a cow to resume oestrous cycles and conceive again to maintain the 365- day calving interval. Literature estimates of the interval between calving and the first oestrous cycle post-calving are 53-82 days for mixed-aged beef-breeding cows and 81-95 days for first-lactation beef-breeding cows (Hickson et al. 2012; Knight & Nicoll 1978; Morris et al. 1978; Smeaton et al. 1986), indicating that a 365-day calving interval is difficult to maintain.

ST, Morris, RE Hickson, NP Martin, and PR Kenyon

Proceedings of the New Zealand Society of Animal Production, Volume 76, Adelaide, 31-33, 2016