[Progress in exploring genes for high fertility in ewes].

ABSTRACT

Fecundity trait in sheep is regulated by some major genes. Among them, BMPR-IB, BMP-15, and GDF-9 are most distinguishing. The mutant FecB of BMPR-IB has multiplicative effects on ovulation. GDF-9's mutants FecGH, FecI, and BMP-15's mutants FecXI, FecXH, FecXG, FecXB, FecXL, and FecXR increase ovulation rate in the heterozygote but result in sterile phenotypes in the homozygote, while GDF-9's mutant, FecGE, only increases ovulation rate in the homozygote. In addition, Woodlands and Lacaune are known as inheritable major genes. Woodlands gene is an X-linked maternally imprinted gene, and Lacaune is similar to FecB with a multiplicative effect on ovulation rate. The size of the effect of one copy of a mutation on ovulation rate ranges from an extra 0.4 ovulations for the woodlands mutation to an extra 1.5 ovulations for the BMPR-IB and Lacaune mutation. Investigation into these genes will not only help to select breeds with high fertility, but also give a chance to further elucidate the mechanism involved in the phenomenon. This review summaries the source, location, phenotype, and mechanism of the major genes in all breeds of sheep.