Effect of season on the resumption of postpartum cyclic ovarian activity in Mouflon ( Ovis gmelini musimon) and Manchega sheep ( Ovis aries)

Abstract

The objective of this study was to compare ovulatory activity of Mouflon and Manchega ewes lambing at different times of the year. A total of 38 adult European Mouflon and 26 Manchega ewes were divided into two groups according to whether lambing occurred in late winter/early spring or summer. Plasma progesterone concentrations were monitored to assess the interval to first ovulation after parturition. Both season and type of sheep affected the postpartum interval. When parturition occurred towards the end of the breeding season for Mouflon (February–March), 12 of 26 animals had a mean (±s.e.) interval to first ovulation of 25 ± 1.8 days and exhibited between 1 and 6 short or normal cycles before the onset of anoestrus. The remaining 14 animals did not resume ovulatory activity until the following breeding season which started in October. Similarly, female Mouflon ( n = 12) giving birth in June reinitiated their breeding activity only at the start of the following season in October. Manchega ewes that lambed in April ( n = 11) and June ( n = 15) had postpartum intervals to first ovulation of 111.5 ± 4.1 and 31.5 ± 1.9 days, respectively. Both groups of Manchegas reinitiated ovulatory activity at the start of the expected breeding season for the breed (July). It can be concluded that the time of year is a major factor controlling the duration of ovarian inactivity following parturition in both Mouflon and Manchega ewes.