Researches On The Changes Of Reproductive Hormones And The Induction Of Estrus During Lactation In Yanshan Cashmere Goats

The research consisted of two experiments the first was conducted to study the changes of reproductive hormones in postpartum female goats and the second was to evaluate the effects of induction of estrus during lactation period on estrus and related reproductive hormone concentrations in Yanshan Cashmere goats.In order to provide technical guidance for breeding and improving reproductive efficiency of the cashmere goats during lactation.Experiment 1:this research was to evaluate the changes of reproductive hormones in 45 days postpartum in female goats.Ten healthy female goats during postpartum were used in this study.The day of lambing was recorded as the 0th day of the experiment.Blood samples were collected on 12 h and every 5 days after lambing,total 10 times,analyzing the changes of FSH,LH,PRL,P₄ and E₂.The results showed that the FSH and LH levels of ewes were lower in the early postpartum period,and the concentrations were lowest on day 10,which was significantly lower than those on days 15,20,25,30,35,40 and 45?P<0.05?.The FSH and LH reached the highest level during the whole experiment period.Except the 40th day,the FSH was significantly different from the other days?P<0.05?.Except the days35 and 40,the LH was different from the other days?P<0.05?.The concentration of PRL in the postpartum serum of the ewes first rises and then decreases.The concentration of PRL was highest on day 10,which was significantly higher than those on days 15,25,30,35,40 and 45?P<0.05?.And it was lowest on day 45 and lower than the days 0,5,10,15 and 20?P<0.05?.The concentration of E₂ was lowest on day 0,which was significantly lower than those of days 15,20,25,30,35,40 and 45?P<0.05?.And it was highest on day 40,which was significantly higher than day 0,5,10,15,20 and 30?P<0.05?.P₄ was lowest on day 10,significantly lower than the day 25,30,35,40 and 45?P<0.05?,and highest on day 35,significantly higher than days 0,5,10,15,20,25,and 30?P<0.05?.Experiment 2:this research was to evaluate the effects of induction of estrus during lactation period on estrus and related reproductive hormone concentrations in Yanshan Cashmere goats.Forty-five lactating goats?BW 45 kg?were randomly assigned into group A,B and C.Progesterone vaginal silicone plugs and FSH were used on days 25,35 and 45 of lactation,respectively.CIDR was inserted into the vagina of all ewes and was removed after 13 days.12 h before the end of the CIDR treatment period,animals received 50 IU and 25 IU FSH respectively.The rate of estrus was recorded within 96 h after sponge withdrawal.Blood samples were collected on days 0,4,9,13 after sponge insert and the onset of estrus?14¹5 d after embedding?.The non-oestrous goats collected blood after the end of estrus,and tested for FSH,LH,PRL,P₄ and E₂ concentrations.Results showed that,Rates of estrus within 96 h in group A,B and C were 60%,53.33%and 80%,respectively,and estrus mainly occurred in 24⁷2 h.There were no differences in FSH,LH,PRL,E₂ and P₄ in groups A,B and C on day 0.FSH and LH reached the minimum on day 13 after sponge insert and increased after sponge withdrawal.In 14¹5 d,FSH and LH in oestrous goats were higher than non-oestrous goats,but only FSH has difference in group A and B?P<0.05?.In 14¹5 d,the concentration of PRL is the lowest.In experiment period,except for the 9th day,PRL in oestrous goats of group C was lower than non-oestrous goats?P<0.05?,but no difference in other groups.In 14-15 d,E₂ in oestrous goats was increased and P₄ decreased;E₂ was higher than those during treatment with vaginal suppositories?P<0.05?.In the experiment period,there were no differences in E₂ and P₄ between oestrous and non-oestrous goats.3)Over days 0 to 15 after the insertion of vaginal suppositories,there were no differences in PRL and P₄ between oestrous and non-oestrous goats,and no differences were observed in FSH of oestrous goats among 3 groups,so as to E₂ of non-oestrous goats.On day 4,FSH of non-oestrous goats in group A was lower than group B?P<0.05?,and LH of non-oestrous goats in group A was higher than group C?P<0.05?.On day 13,LH of oestrous goats in group B was lower than group C?P<0.05?.On days 14¹5,E₂ of oestrous goats in group B was higher than group C?P<0.05?.In conclusion,FSH,LH,E₂ were increased in wave within 45 days postpartum.PRL maintained at a higher level within 10 days after delivery,and then fluctuated downward.The P₄ was increased from15 to 35 days postpartum.The rate of induced estrus was highest on day 45 of lactation.Exogenous progesterone dramatically decreased the PRL concentration.The secretion peaks of FSH,LH and E₂were appeared simultaneously in estrus.