Abstract
Both heat detection and timely insemination contribute to the optimization of fertility management on farm. In this study, 4 systems were compared for their ability to accurately detect heat and relate to the LH surge preceding ovulation in dairy cows. As the moment of LH surge has been reported to correlate strongly with time of ovulation, the potential to predict the optimal insemination can in this way be evaluated. The systems included were the traditional visual observation of heat, activity attentions and 2 progesterone-based methods. For the latter, it was also investigated whether the prediction of the LH surge could be improved by fitting a longitudinal model to the progesterone data. First, the systems were compared in terms of sensitivity and positive predictive value for heat detection. Then, the time interval between the attentions and the LH surge was investigated. The range on this interval was used as main criterion to evaluate the time-relation between the heat attention and the LH surge. The smaller this range, the better the correlation with the LH surge, and accordingly, ovulation. Heat attentions based on visual observations were noted from 4 hours before until 5 hours after the LH surge (range of 9 hours), indicating a high correlation. However, they also had the lowest sensitivity to detect heat (40%), making it less useful on-farm. Using activity-attentions proved more sensitive (80%), but was less accurate. Moreover, these attentions had the least accurate correlation with the moment of the LH surge and were observed from 39 hours before until 8 hours after it (range of 47 hours). Attentions based on milk progesterone measurements through the detection of luteolysis preceding a follicular phase correctly identified all estrous periods. Alarms generated when the smoothed progesterone level crossed a 5 ng/mL threshold, were followed by the LH surge after 21.6 to 66.4 hours (range of 44.8 hours). The model-based approach performed slightly better with attentions generated 48.8 to 81.2 hours (range 32.9 hours) before the LH surge.
INTERPRETIVE SUMMARY. Heat detection attentions and LH surge. Adriaens Both detection of heat and timely insemination are important factors in optimizing fertility management. The latter is dependent on ovulation time, which is preceded by the LH surge. In this study, the performance of 4 heat detection systems at predicting the LH surge was evaluated. Visual observation of standing heat correlates best with the LH surge, but is the least sensitive, while activity attentions are the least reliable. Using milk progesterone, one can reliably detect luteolysis, which in healthy cows is followed by the LH surge about 62 hours later.