| Sumario: | This study examined estrus response, estrus response interval and pregnancy rate of Bos indicus and B. indicus x B. taurus crossbred cows and heifers after oestrus synchronization. A total of 101 non-pregnant and cycling animals, composed of 63 Boran (46 heifers and 17 cows) and 38 Boran-Simmental crossbreds (23 heifers and 15 cows) were treated with 2 ml of PGF2 analogue (Estrumate) intramuscularly. The overlal estrus response within 120 hr of treatment was 38.1 percent for cows and 71.1 percent for heifers. Crossbred heifers (78.3 percent) and cows (46.7 percent) responded better than Boran heifers (65.2 percent) and cows (29.4 percent), respectively. The mean estrus response interval was shorter in heifers (58.3 hr) than cows (75.0 hr). However, the overall pregnancy rate was basically similar, 54.3 percent in cows and 59.8 percent in heifers. The overall result achieved in the study was acceptable and the procedure used could be adopted to produce uniformly pregnant animals to farmers to allow systematic on-farm performance evaluation.
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