Indução da atividade sexual em ovelhas corriedale mediante controle da luminosidade

Abstract

The object of this study was to verify the effect of two types of illumination simulating day lengths of spring and winter on the sexual activity of ewes and to compare it with that of a normal summer season. 109 ewes (33 matured age 3.5 years and 76 maiden age 2 years) were used in randomized groups. In the first experiment, with an artificially increased spring daylength, the ewes did not show oestrus activity like those under natural daylength except for one animal (1.4%). The second group, with natural daylength of the sexual season (summer), the frequency and accumulated frequency of oestrus was only 28.5% and 28.5% (January), 100% and 100% (February) and 100% and 185.7% (March). Also observed for the second group were cycle interval of 19.8 ±3.6 days,ovulation rate of 1.07 and cervical mucous crystallization 68.1 % of the total crystallization. The third group (8h light and 16h darkness, winter) showed frequency and accumulated frequency of induced oestrus of 85.7% and 171.4% (July), 71.4% and 100% (August) and 42.8% and 42.8% (September). Also observed for the third group were a cycle interval of 18.1 ±2,4 days, ovulation rate of 1.0 and cervical mucous crystallization of 90.8% of the total. When comparing the data from artificial illumination of winter with normal summer illumination, no significant differences were observed for the oestrus interval nor the number of corpora lutea in the ewes. In conclusion, the abrupt seriation modified daylength in winter was favorable for sexual activity in young ewes.