Behavioural signs of estrus and their relationship to time of ovulation in Zebu (Sahiwal) cattle

The present study reports the behavioural signs of estrus, their temporal distribution and duration of expression and their relationship with the time of ovulation in zebu cattle in order to identify the reliable sign(s) of estrus that could fairly predict the ovulation time. The onset, intensity and expression of various signs of estrus were continuously recorded till ovulation in 60 Sahiwal cows. Time of ovulation was determined by ultrasound examinations at 2 h interval. Estruses were mostly of moderate (52%) or weak (34%) intensity. Mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane appeared early in relation to the ovulation time (31.27 ± 1.97, 31.05 ± 2.98 and 30.79 ± 2.53 h, respectively) in comparison to mounting (27.67 ± 2.33 h) and standing to be mounted (25.37 ± 2.11 h). Mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane persisted significantly more duration (P < 0.01) than mounting and standing to be mounted. Further these cardinal signs appeared early in relation to time of ovulation, persisted for longer duration and expressed intensely. We conclude that mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane can be good predictor ovulation in this breed of cattle.