营养补饲和定时输精技术对牦牛繁殖效率的综合调控OA

This study investigated the effects of nutritional supplementation and the implementation of es-trus synchronization-timed artificial insemination technology on the reproductive performance of female yaks.The experiment was simultaneously carried out in Madoi County,Guoluo Prefecture,Henan County,Huangnan Prefecture,Nangqian County,Yushu Prefecture,and Jianzha County,Huangnan Prefecture in Qinghai Province.The numbers of female yaks used in each experimental site were 200,100,80,and 200,re-spectively.All yaks were randomly and equally divided into an experimental group and a control group based on body weights.The experiment was divided into two phases.The first phase was the nutritional supplementation stage.In the experimental group,female yaks were fed a formulated nutritional diet of 1.0 kg per head at 18:00 every afternoon,and they naturally grazed with the control group of yaks in during the rest of the time.The female yaks in both groups were weighed on the 1st,45th,and 90th days.In the second phase,the female yaks in the experimental group was subjected to a synchronous estrus timed artifi-cial insemination protocol.Blood samples were collected on the 0th,7th,and 9th days of the treatment to measure the reproductive hormone levels.The estrus rates were counted on the 8th and 9th days,as well as the infection rates of endometritis and vaginitis in female yaks with and without vaginal irrigation after 7 days of treatment.The female yaks in the control group mated naturally.The estrus rates of both groups of yaks were counted,and pregnancy examinations were conducted 180 days after mating to calculate the con-ception rate.The results showed that during the nutritional supplementation phase,the average daily weight gain of female yaks increased significantly from(51±21.8)-(85±22.2)g/d in the control group to(260±21.5)-(305±21.1)g/d in the experimental group(P≤0.05).After implementing the synchronized estrus and timed insemination protocol,the levels of reproductive hormones(E2,LH,FSH,GnRH)in es-trous yaks on the 7th and 9th days were significantly higher than those in non-estrous female yaks(P ≤0.05).However,there was no significant difference in GnRH levels between estrous and non-estrous female yaks in Nangqian County on the 7th day(P＞0.05).The estrus rate on the 8th day was 44.74％-52.01％,significantly higher than that on the 9th day(22.34％-26.25％)(P≤0.05).The estrus rate of female yaks was significantly increased from 17.94％-23.17％in natural estrus to 68.42％-74.35％(P≤0.05),and the conception rate in the estrus cycle was significantly increased from 16.67％-19.51％to 65.79％-75.60％(P≤0.05).When the vagina was flushed with 0.01％potassium permanganate solution on the 7th day after removing the intravaginal sponge,the infection rate of vaginitis in female yaks was significantly reduced from 11.25％-12.31％in the non-flushing group to 1.56％-2.26％(P≤0.05),but there was no significant effect on the infection rate of endometritis(P＞0.05).Due to the relatively long natural estrus cycle,the total conception rate of female yaks in natural estrus was 90.62％-95.54％,significantly higher than that of female yaks treated with estrus synchronization-timed artificial insemination(65.79％-75.60％)(P≤0.05).The above results indicate that nutritional supplementation can increase the weight gain of yaks and improve their body condition.The implementation of estrus synchronization and timed ar-tificial insemination technology can significantly increase the estrus rate of female yaks.Although the con-ception rate has not been improved,the time cost has been reduced.