An evaluation of milk temperature measurement for detecting oestrus in dairy cattle. II variations in body and milk temperature associated with oestrus

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Abstract
Vaginal and milk temperatures were measured at each milking in 15 postpartum Friesian cows showing recurrent oestrous cycles for a total of 33 oestruses. A significant increase (P<0.001) in both vaginal and milk temperature of 0.29±0.05°C was shown between the milking prior to oestrus and the milking when oestrus occurred. Cows were divided into 3 groups: showing either a definite temperature rise (27% of cases), a limited temperature rise (60%) or no temperature change (13%) associated with oestrus. Various methods of analysis were investigated to determine the usefulness of the milk temperature data for oestrus prediction. The optimum compromise of high oestrus detection rate (73.3±16%) and lowest percentage of false positives (10.8±3.0%) was based on a temperature rise on the day of oestrus of ≥0.2°C over the corresponding mean temperature of the preceding three days. These rates suggest the measurement of milk temperature is less useful for oestrus prediction than some earlier reports have indicated.