Interval between calving and first observable oestrus in post-partum Bunaji cows

Sixty-eight post-partum Bunaji cows were used to determine the interval from calving to first oestrus. Thirty and thirty-eight animals calved during the rainy (June to October) and dry (November to May) seasons, respectively. The mean intervals from calving to first oestrus were 152·8 and 122·9 days for the cows that calved during the rainy and dry seasons, respectively. Eight cows that lost their calves immediately after calving showed earlier first post-partum oestrus (58·5 ± 7 days) than those running continuously with their calves irrespective of season of calving. Cows that had calved more than twice tended to show earlier post-partum oestrus than those with only one or two calvings. It is concluded that season of calving and age or parity of dam affect the interval from calving to first observable oestrus in post-partum Bunaji cows.