Production Test Of Tan-sheep With Three Times Lambing In Two Years

At present,with the constant improvement of the scale of Chinese sheep industry,the development of enterprises have gradually shown the characteristics of large-scale,mechanization and information,which requires the steady improvement of the supporting breeding and production efficiency and the supply capacity of sheep products.Tan sheep is one of the nine special pillar industries in Ningxia province,and also a high-quality germplasm resource in China.However,Tan sheep have the problems of long pregnancy,slow growth and late weaning.In order to improve the reproduction performance of the Tan sheep,adapt to the development of intensification,this experiment explores the possibility and practical effect of the mode“Three times lambing in two years”for Tan sheep in Ningxia,which will provide reference for further standardizing and guiding the practical application of this mode.The field experiment with three times lambing in two years of Tan sheep obtained the following results:1.The first lambing test of the field experiment with three times lambing in two yearsThe field experiment with three times lambing in two years began in the fall of 2020,with 555 breeding ewes and 10 breeding rams as objects,using the methods of taking ram as teaser and artificial insemination to carry out breeding and production.The sheep which were estrous again were artificially inseminated repeatedly and a total of three estrous cycle were repeated.Then put the breeding ram and ewes together to make them mate naturally.The unrequited ewes were carried out a pregnancy check with B-ultrasound.The results showed that the average conception rate of natural estrus and artificial insemination was 53.25%while the average conception rate in the second estrous cycle period was 44.30%.Eventually,there were 508 ewes produced lambs due of gestation.Therefore,the total reproductive cycle conception rate was 91.53%.Besides,there were 47 ewes which failed to conceive,or had pregnancy abortion in estrous or premature birth,accounting for 8.47%of the total breeding ewes.In addition,it was found that the ewe pregnancy rate varied greatly with different rams.The first lambing 508 sheep produced 601 lambs with a lambing rate of 118%.The gestation period was calculated as 153.353±3.36 d.Artificial lamb breeding measure was used for lactating lambs and weaning when the lamb weight reached about 4 times as heavy as the newborn lambs.At the same time,the control group was set up without lamb breeding.The results showed that the cultured lambs basically reached the weight when they weaned at 60days,compared with only 41%of the control lambs at 60 days.2.The second lambing test of the field experiment with three times lambing in two yearsThe second lambing experiment was held from March 2021 to November 2021.The ewes in the first experiment were weaned in batches when their lambs reached their weaning weight.A total of 322 early weaned ewes entered the second reproductive cycle.They were treated with CIDR+PMSG+PG to induce estrus.The efficiency rate of induced oestrus was71.43%（230/322）.The first artificial insemination and intramuscular injection of LRH-A₃were performed 12 hours later after induced oestrus.After that,artificial insemination was conducted once every 12 hours.A total of 2～3 times artificial insemination according to the duration of estrus.There were 131 ewes gestating.Therefore,the conception of the second lambing induced estrous ewes was 56.96%（131/230）,the gestation period is 151.62±3.32 d,lambing rate 118.32%（155/131）,and the survival rate of the weaned lambs was 94.29%.It is comprehensively calculated that the pregnancy time of pregnant ewes in the first estrus period and the time of lamb breeding are 211.62 days.If adding 19 days,the time of induced oestrus and breeding,it needed 230.62 days,which is less than breeding interval 240 days which is distributed by per breeding cycle in three times lambing in two years.3.The third lambing test of the field experiment with three times lambing in two yearsAfter early weaning of the second lambing breeding ewes,the third lambing began in November 2021.A total of 271 early weaned ewes（including the second pregnancy and the same period in the experiment）entered the third lambing production test.The ewes were induced by CIDR+prolactin antagonist+PMSG+PG,with an estrous response rate of71.59%（194/271）.There were 149 ewes gestating.The conception rate of the third lambing-induced estrous ewes was 76.41%（149/194）according to the B ultrasound pregnancy check.Conclusions:（1）Three times lambing in Two Years were used to induce estrus of early weaned Tan ewes by CIDR+PMSG+PG-CL,and the estrus induction effect of the second parities（spring）and the third parities（winter）was over 71%.That is,induction of early weaning ewes can be used as a two-year and three-fetal estrus technique to make most ewes normally estrus.（2）Strengthen perinatal management,and when lambs are 10 days old after birth,the lambs can be weaned at about 60 days by using 80%lamb pellet feed and 20%high-quality alfalfa meal.The survival rate of lambs was increased by about 10%（the survival rate of other lambs was 85%）.（3）The field experiment with three times lambing in two years improve the breeding efficiency and economic benefits of Tan sheep,and it serves as guidance and reference for the efficient breeding and production of Tan sheep.（4）The gestation period of the first litter of Tan sheep in autumn was 153.35±3.36 days,and the gestation period of the second litter in spring was 151.62±3.32 days.It indicates that there is a long gestation period in tan sheep.（5）There was a significant difference in estrus induction efficiency in early spring weaning ewes,the best effect was in April,but the estrus induction efficiency decreased after entering May.There was no significant difference in estrus induction efficiency among early weaned ewes in different winter months.（6）In the field experiment with three times lambing in two years of Tan sheep,25.79%（131/508）of the ewes completed three times lambing within two years.On the basis of summarizing the production test methods and results,further effective measures can be taken to further improve the proportion of breeding ewes which produce three times lambing in two years.