Reproductive performance in seasonally anestrous ewes treated with exposure to ram with reference to the effects of feeding level around early mating period and PMSG-PGF_(2#alpha#) treatment

摘要

This study aims to compare the reproductive performance of seasonally anestrous ewes which were exposed to ram starting from 94 days after lambing; fed with 2 different level of TDN at early mating period; hormonally treated with PMSG and PGF_92#alpha#).Forty-five Suffolk ewes weaned at 73 days after lambing were divided into following 4 groups namely:Group H0 - exposed to ram for 39 days; consumed 1.15kg TDN/dayGroup H1 - exposed to ram for 39 days; consumed 1.15kg TDN/day; hormonally treated at 13 days after exposure to ram with PMSG (500IU) and PGF_(2#alpha#) (15mg)Group H0 - exposed to ram for 30 days; consumed 0.89kg TDN/dayGroup H1 - exposed to ram for 39 days; consumed 0.89kg TDN/day; hormonally treated at 13 days after exposure to ram with PMSG (500IU) and PGF(2#alpha#) (15mg)All groups of ewes were maintained on natural daylength or supplemented with 20-24 hours of artificial lighting during perinatal period. Fisher's exact probability test was adopted to detect statistical difference among groups.The incidence of estrus and pregnancy rate was higher than 92 percent and 50 percent respectively in all groups, however, there was no significant difference among treatment groups. The daylength pattern during perinatal period had also no significant effect on the incidence of estrus and pregnancy rate. Intake of 1.15kg of TDN/day improved the daily gains of ewes in group H0 and H1, however, failed to show significant effect on the incidence of estrus and pregnancy rate.In conclusion, this study was able to demonstrate that exposure of ewes to ram withou hormonal treatment successfully induced fertile estrus. Moreover, exposure to ram in combination with PMSG-PGF_(2#alpha#) treatment induced cyclic ovarian activity and synchrony of estrous time was achieved.