Post-parturn oestrous interval of single-suckled Angus beef cows

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Abstract
Some factors that may influence the interval from calving to first post-partum oestrus in 61 single-suckled Angus cows calving in the spring of 1975 were investigated. The overall least squares mean for this interval was 79.2 days. Calving date significantly (P < 0.01) influenced this interval, but the effects of management group, age of dam, sex of calf and post-calving nutritional treatments were non-significant. Milk production of the dam, as assessed by the weigh-nurse-weigh method, was correlated (P < 0.05) with post-partum interval at 20 days (r = 0.25), but not at 40 or 60 days. The mean calving interval for the herd was 367.6 days, calving interval being correlated (P < 0.05) with post-partum interval to first oestrus (r = 0.29). It was concluded that attention should be given to pre-calving nutrition, but during the first 40 days post-partum, cows can be fed to maintain their live weight without detriment to their reproductive performance.