A field study on estrus detection in lactating beef cattle.

摘要

878 lactating beef cows in 60 French herds were studied. The average herd size was 48; 75% of the farmers partly or exclusively used AI. The cows calved between October 1992 and March 1993. Oestrus was recorded daily by the farmers. Cycling status was determined by progesterone radioimmunoassay 2 months after calving. The relationship between the oestrus detection protocol and the delay period from calving to first observed oestrus was analysed using survival curves and the Cox proportional hazardmodel, adjusting for confounders. 71% of the cows were seen to be in oestrus by the farmers; the interval between calving and first observed oestrus ranged from 9 days to more than 5 months and the median was 56 days. Two months after calving, 44% of thecycling cows had not been seen in oestrus by the farmers and 11% of the non-cycling cows had been reported to have been in oestrus. The oestrus detection protocols used by farmers varied widely with respect to the oestrus signs considered and time spentlooking for signs. Two factors were related to a shorter interval between calving and first observed oestrus: the use of AI (which was related to the farmer's interest in oestrus detection) and an overall daily time spent on oestrus detection of >1 h. Cows in tie stalls had a delayed interval to first observed oestrus.