[Annual variations in estrual behavior, rate and possibilities for ovulation in Peulh ewes from Niger].

Annual variations in estrous and ovulation behavior were studied in 23 bicolored Peulh ewes for a period of 30 months. The percentages of estrus and ovulation shown over a year of observation were 76 and 86%, respectively. The average rate of ovulation was 1.3 +/- 0.04 (X +/- SEM). Reproductive activity was minimal from January to April, as the percentages of estrus and ovulation varied between 43.8 and 61% and between 53.1 and 86%, respectively. This period was marked by the advent of anestrus, interrupted frequently by silent and irregular ovulations. Anestrus lasted an average of 81.9 +/- 9.8 days (X +/- SEM). Reproductive activity was maximal from May to December, as the percentages of estrus and ovulation varied between 77 and 97% and between 87.5 and 100%, respectively. During this period ovarian activity was interrupted by prolonged diestrus which lasted an average of 24.9 +/- 3.3 days (X +/- SEM). The ovulation rate did not differ significantly (P greater than 0.05) between periods of minimal and maximal sexual activity. These results suggest that the reproductive potentialities of Peulh sheep on a good diet are comparable to those of certain ovine breeds in temperate zones. The results also suggest that anestrus in bicolored Peulh sheep is probably a different physiological process than the one observed in some breeds of sheep in which anestrus is marked by total ovarian inactivity.