Accuracy of oestrus detection in cows and its economic impact on Shiraz dairy farms

No report has been published on the economical losses associated with errors in oestrus detection in cows under Iranian intensive dairy management. The following study was carried out to determine the accuracy of oestrus detection by farmers using artificial insemination in Shiraz dairy farms. Milk samples were collected from 179 Holstein milking cows at the time of artificial insemination. Milk progesterone concentration was determined using a commercial radio-immunoassay kit. It was assumed that a milk progesterone concentration greater than or equal to 3 ng/ml indicated the presence of active luteal tissue and that all animals in oestrus had a concentration less than 1 ng/ml. Results of the present study showed that error in oestrus detection was higher in dairy herds with more than 85 milking cows compared to that of the smaller size herds (14.4 vs 7.3%; χ2 = 2.59; P = 0.1). Five out of 11 herds (45%) had an oestrus detection error higher than 10 percent while in the remaining six herds the oestrus detection error varied from 0 to 7.1%. Based on the assumptions and calculations made in the present study, the net cost of one day delay in conception for a cow producing 25 litres milk in peak lactation was calculated at 40591.98 Rials (4.51 $US) when conception is delayed from 85 to 100 days post-calving, increasing to 60120.89 Rials (6.68 $US) per day if conception occurred at 146 to 175 days post-calving.