AUTHOR=Wang Xiangyu , Guo Xiaofei , He Xiaoyun , Liu Qiuyue , Di Ran , Hu Wenping , Cao Xiaohan , Zhang Xiaosheng , Zhang Jinlong , Chu Mingxing 

TITLE=Effects of FecB Mutation on Estrus, Ovulation, and Endocrine Characteristics in Small Tail Han Sheep

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.709737

DOI=10.3389/fvets.2021.709737

ISSN=2297-1769

ABSTRACT=<p>The Booroola fecundity gene (<italic>FecB</italic>) has a mutation that was found to increase the ovulation rate and litter size in Booroola Merino sheep. This mutation is also associated with the fecundity of small-tail han (STH) sheep, an important maternal breed used to produce hybrid offspring for mutton production in China. Previous research showed that the <italic>FecB</italic> gene affects reproduction in STH sheep, based on litter size records. However, the effects of this gene on estrus, ovulation, and endocrine characteristics in these sheep remain unclear. Here, we analyzed the traits mentioned earlier and compared them among the three <italic>FecB</italic> genotypes of STH ewes using estrus synchronization. Overall, 53 pluriparous ewes were selected from among 890 STH ewes and subjected to <italic>FecB</italic> genotyping for experiments to characterize estrous and ovulation rates. <italic>FecB</italic> heterozygous (+B) ewes presented an earlier onset of estrus (42.9 ± 2.2 h) and a shorter estrous cycle (17.2 ± 0.2 days) (<italic>P</italic> ≤ 0.05). The ovulation rates increased with the increasing copy number of the B allele (<italic>P</italic> ≤ 0.01). Ovulation time showed no significant differences among the three <italic>FecB</italic> genotypes. The serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone, estrogen (E<sub>2</sub>), and progesterone (P<sub>4</sub>) were measured in 19 of the ewes. Serum concentrations of E<sub>2</sub> and FSH dramatically varied around the time of behavioral estrus. In <italic>FecB</italic> mutant homozygous (BB) ewes, E<sub>2</sub> concentration had two peaks, which were higher (<italic>P</italic> ≤ 0.05) than those of ++ genotypes. FSH concentration of BB ewes was higher (<italic>P</italic> ≤ 0.05) than that of the ++ ewes just after estrus. The expression of the estrogen receptor 1 (<italic>ESR1</italic>) gene in the +B genotype was higher than in the other genotypes. Based on the data for the reproductive performance of STH ewes with the three <italic>FecB</italic> genotypes, our study suggests that the development of follicles in ewes with the B allele is dependent on the response to FSH regulated by E<sub>2</sub> in the early stage. +B ewes, exhibiting moderate ovulation and litter size and a shorter estrous cycle, can be highly recommended in sheep crossbreeding systems for commercial mutton production. Moreover, this study provides useful information to conserve better and use the genetic resources of STH sheep in China.</p>