Temporal changes in endogenous estrogens and expression of behaviors associated with estrus during the periovulaory period in Murrah buffaloes (Bubalus bubalis)

The objective of this study were (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. Estrus and its behavioral signs were detected at hourly intervals by visual observations, per recta examination of genitalia and bull parading four times in a day for 30 minutes each. Among the behavioral signs of estrus, swollen vulva (80%) was the best indicator of estrus followed by excitement (70%). Among the duration of behavioral estrus signs the first and longest duration of estrus signs was swollen vulva which was seen upto 19.8 +/- 0.8 h after onset of estrus. The mean total duration of estrus symptoms from appearance to disappearance of all the behavioral estrus symptoms was 23.5 +/- 1.7 h. All the behavioral estrus symptoms were observed during the period of estrogen surge. Endocrine profile during the periestrus period showed that the mean peak concentrations of total estrogen 23.9 +/- 3.9 pg/ml occurred at 8.8 +/- 1.7 h after onset of estrus. The average number of estrus symptoms observed per animal during onset of spontaneous estrus was 5.7. Ovulation occurred after 37.4 +/- 1.7 h after onset of estrus and 13.4 +/- 1.0 h after end of total estrogen surge respectively. In conclusion, our results suggest that all signs of behavioral estrus occurred during the preovulatory rise in estrogens. The first sign of estrus to be observed was a swollen vulva and this symptom persisted the longest.