Studies On Effects Of Season On Reproductive Performance Of Meat Breed Sheep Rams

The rams' reproductive performance of two introduced meat breeds (Poll Dorset and Borderdale) had been evaluated from April in 2001 to April 2002.The results showed that: (l)the lowest ejaculate volume of Poll Dorset as well as Borderdale was in May. The highest ejaculate volume of Poll Dorset was in March, but Borderdale' s was in November. The seasonal variation of the two breeds was different. The partial correlative between the ejaculate volume and the scrotal circumference was 0. 3071(p<0.01) and that between ejaculate volume and response time was 0. 1649(p<0. 05). (2)The two breeds had high fresh sperm motility . The highest fresh sperm motility of the two breeds was in January and the lowest in May. In winter that of the two breeds was high (Poll Dorset 0.78, Borderdale 0. 77) and in summer was low (Poll Dorset 0. 72, Borderdale 0. 70). The difference cf the fresh sperm motility between the two breeds was not significant. (3) The seasonal variation of sperm cell concentration were different. The highest sperm cell concentration of Poll Dorset was in autumn (35. 63X lOVml) and the lowest in spring (32. 69XloVrol), but the highest of Borderdale was in winter (40. 37X10*/ml) and the lowest in summer (35. 57X10K/ml). The partial correlative between the sperm cell concentration and the ejaculate volume was 0. 2436 (p=0.01) and that between the sperm cell concentration and the scrotal circumference was 0. 3890(p<0. 01). (4)The highest total sperm abnormalities of Poll Dorset was found in December (19. 06%)and the lowest in July (8.88%), but that of Borderdale was the highest in May (18.05%)and the lowest in October (8.94%). The partial correlative between total sperm abnormalities and sperm cell concentration was - 0.1967(p<0.05) and that between total sperm cell abnormalities and response time was 0. 1442 (p=0. 065). (5)The highest thawed sperm motility of the two breeds were both in September and the lowest in May. There were no significant differences between the two breeds in thawed sperm motility (p>0. 05). (6)The highest content of the testosterone in semen of the two breeds were separately in November (1779. 8 pg/ml) and August (2217. 7 pg/ml), and the lowest were separately in July and October. Both of the two breeds had the similar seasonal variation of the testosterone in semen, and the highest in winter and the lowest in summer. (7)The highest response time of all those tested sheep was in spring and the response time between thespring and the summer, autumn and winter was significantly different. The difference of that among summer, autumn and winter weren' t significant. (8)The largest scrotal circumference of the two breeds were separately in July and august and the smallest separately in January and April. There was excellent significance (p<0. 01) of the scrotal circumference between the two breeds, but both were larger in autumn and smaller ill spring. Of all the tested aspects of the reproductive performance of the two breeds the Borderdale was better than Poll Dorset. (9)A1 though there were high temperature in the end of the summer and the early autumn, it was lower than the physiological temperature. The partial correlation between meteorological elements and the tested reproductive performance aspects told us that the meteorological factors' effects on the quality of the semen were complicated. The meteorological factors are suitable to bring the reproductive performance of the two introduced breeds into play.