Effect Of BMPR-IB Genotype On Three Reproduction Techniques In Sheep

Sheep industry plays a pivotal role in animal husbandry in China,providing a large number of animal products such as meat,skin,hair and wool for the people,and is an important economic source for herdsmen.As one of the most important economic traits,the reproductive traits of sheep is the prerequisite basis for the productive and high-yield sheep industry,which determines the overall economic benefit and has been the focus of domestic and foreign research.With the rapid development of molecular biology technology,some major genes controlling the sheep’s reproductive traits have been discovered one after another,laying a foundation for improving the sheep’s reproductive performance genetically.The BMPR-IB（FecB）gene,discovered in 2001,is the most well-known major gene for prolificacy identified at present.It has a significant effect on improving the ovulation rate and lambing number of sheep under natural reproductive conditions.It has a significant effect on ovulation rate and lambing number of sheep under natural reproductive conditions,and has been widely applied in sheep breeding and production,achieving good results.However,the effect of the BMPR-IB（FecB）gene in the application of artificial reproduction techniques such as estrus synchronization,artificial insemination and multiple ovulation is still unclear.In this study,231 healthy small tail sheep with normal reproductive conditions were selected as the experimental donors,and the genotypes of BMPR-IB（FecB）were identified by PCR-RFLP technology,so as to determine the gene frequency and genotype frequency;to analyze the effects of each genotypes under various artificial reproduction techniques（with the use of various artificial hormones）to provide a theoretical basis for more fully and rational use of the BMPR-IB（FecB）gene.The experimental results are as follows:（1）The frequencies of FecB^BB,FecB^B+and FecB⁺⁺genotypes were 0.5065,0.4026 and 0.0909,respectively.The allele frequencies of B and+allele was 0.7078 and 0.2922,respectively.（2）After estrus synchronization,more than 90.00%of ewes exhibited overt estrus signs,and no differences were observed among three genotype groups（P=0.878）.Estrus onset in the three groups all occurred between 36 to 60 hours after sponge removal,and no difference were observed among groups（P=0.624）.The estrus duration in FecB^BB group,FecB^B+group and FecB⁺⁺group was42.67±1.61 h,44.14±1.39 h and 46.67±1.91 h（P=0.829）.（3）On day 60 after artificial insemination,there was no difference in pregnancy rate among FecB^BB group,FecB^B+group and FecB⁺⁺group（P>0.05）.Compared to ewes in the non-carrier group,lambing and fecundity rates of the B allele group increased obviously（one copy resulted in an increase of 0.88 lambs and two copies produced an additional 0.41 lambs;P<0.01）.Confirmed that the B allele had an additive effect on lambing number.（4）After multiple ovulation,the average number of embryos production among the FecB^BBgroup,FecB^B+group and FecB⁺⁺group were 9.16±0.79,8.20±0.77 and 8.44±0.61,and the number of grade 1-2 embryos were 7.11±0.80 pieces,6.70±0.73 pieces and 7.06±0.67 pieces,the difference among different genotype groups was not significant（P>0.05）,The effect of B allele had no difference on the number of embryos recovered and embryos of grade 1-2;the fertilization rate of egg cells in FecB^B+group（92.07%）and FecB⁺⁺group（90.13%）was slightly higher than that in FecB^BB group（88.51%）,but the difference was not significant（P>0.05）.（5）The body weights of the offspring of the FecB^BB group,FecB^B+group and FecB⁺⁺group were 2.94±0.096 kg,2.98±0.080 kg and 3.65±0.180 kg;the weaning weights were 13.13±0.32 kg,13.85±0.33 kg and 15.12±0.57 kg.Due to the increase in the lambing number in the FecB^BB group and the FecB^B+group,the birth and weaning weights of the lambs in both groups were lower than those in the FecB⁺⁺group（P<0.01）.The weaning survival rates of lambs among the three groups were 84.78%,86.96%and 94.12%,and there was no difference among three genotype groups（P>0.05）.Our research results indicated that after estrus synchronization,there was no difference in estrus rate,time to estrus onset,estrus duration,etc.After artificial insemination,the B allele caused an increase in the lambing number.After multiple ovulation,there was no significant difference in recovered embryos among genotype groups.Due to the higher prolificacy in ewes carrying the B allele was associated with a reduction in offspring body weight at birth and weaning.