不同同期发情处理及蛋白营养补给对非发情季节放牧生产欧拉羊发情率及血液激素水平影响OA

[Objective]Oula sheep are an important meat-purpose breed of Tibetan sheep on the Qinghai-Tibet Plateau.However,due to pasture shortages during the long cold season and their seasonal estrus pattern,the estrus rate of grazing Oula sheep during the non-estrus season is extremely low,which severely limits batch production and farming efficiency.This study therefore sought to identify a cost-effective and easy-to-apply estrus synchronization protocol for grazing Oula sheep at the end of the cold season that would provide technical support for batch reproduction.[Methods]The study was conducted at a hornless Oula sheep cooperative in Henan Mongolian Autonomous County,Huangnan Prefecture,Qinghai Province.A total of 160 healthy,multiparous,2.5-year-old hornless Oula ewes with similar body weights were randomly assigned to 16 groups of 10 animals each.Four nutritional levels were compared:natural grazing alone,and natural grazing supplemented with concentrates containing 16%,18%or 20%crude protein.Three estrus synchronization protocols were also applied:two injections of cloprostenol(PG);insertion of a flurogestone acetate sponge(Progesterone-releasing intravaginal device,PRID)combined with a PG injection;and an injection of gonadorelin(Gonadotropin-releasing hormone,GnRH)combined with a PG injection.The experiment lasted 10 days.Blood samples were collected at the beginning and end of the experiment,and serum concentrations of estradiol(E2),progesterone(P),luteinizing hormone(LH)and follicle-stimulating hormone(FSH)were measured using enzyme-linked immunosorbent assay.Estrus rates were determined at the end of the experiment by teasing with a ram.[Results]Under natural grazing conditions during the non-estrus season,Oula sheep did not show estrus(0%estrus rate).After concentrate supplementation,natural estrus began to appear.Supplementation with 18%or higher protein concentrate increased the natural estrus rate to 30%.Treatment with exogenous hormones alone under natural grazing conditions produced estrus rates of 30%-40%.Combining nutritional supplementation with estrus synchronization treatment further increased estrus rates,with the highest rate(60%)observed in the group that received 18%protein supplementation combined with the GnRH+PG protocol.Hormone measurements revealed no significant differences in serum E2 or LH concentrations among the groups(P>0.05).The GnRH+PG group had significantly higher serum FSH concentrations than the other groups(P<0.05),while the PRID+PG group had significantly higher serum P concentrations than the other groups(P<0.05).[Conclusion]At the end of the cold season on the Qinghai-Tibet Plateau,short-term supplementation with 18%or higher protein concentrate effectively induces natural estrus in Oula sheep during the non-estrus season,but the resulting estrus rate remains modest.Adding exogenous hormone treatment to nutritional supplementation improves the estrus rate further.The combination of short-term 18%protein supplementation with the GnRH+PG protocol achieves approximately 60%estrus synchronization at a manageable cost and is recommended for batch reproduction of grazing Oula sheep during the non-estrus season.