Changes in endogenous estrogens and expression of behaviors associated with estrus during the periovulatory period in Heatsynch treated Murrah buffaloes (Bubalus bubalis).

The objective of this study was (1) to establish the duration of behavioral estrus signs and timing of ovulation in Murrah buffaloes (n = 10) and (2) to determine relationship between behavioral estrus signs with change in plasma estrogen concentrations in animals treated with Heatsynch protocol. Estrus and its behavioral signs were detected at hourly intervals by visual observations per rectal examination of genitalia and bull parading four times in a day for 30 min each. Among the behavioral signs of estrus, swollen vulva was the best indicator of estrus followed by excitement and chasing by bull (90%). Among the duration of behavioral estrus signs, the first and longest duration of estrus signs was swollen vulva, which was seen up to 21.6 +/- 1.1 h after onset of estrus. The mean total duration of estrus symptoms from appearance to disappearance of all the behavioral estrus symptoms was 40.2 +/- 1.8 h. Endocrine profile during the periestrus period showed that the mean peak concentrations of total estrogen 330.9 +/- 108.3 pg/ml occurred at 9.6 +/- 1.0 h after estradiol benzoate injection. The average number of estrus symptoms observed per animal during Heatsynch treatment was 7.1. Ovulation occurred after 50.0 +/- 2.0 h after estradiol benzoate treatment and 26.7 +/- 2.0 h after end of total estrogen surge, respectively. In conclusion, our results suggest that all signs of behavioral estrus occurred after the preovulatory rise in estrogens. The first sign of estrus was swollen vulva, and this symptom persisted the longest.