Inverdale fecundity gene (FecX^I) influences twin ovulation incidence in pubertal ewe lambs from Texel sires and Cheviot or Scottish Blackface dams

Abstract

A key to long-term sustainable enhancement of viable livestock production is the introduction of genetic traits that ensure that fertility and meat quality characteristics are compatible with farming environments and market needs. For example, the sheep industry could benefit if daughters of hill-breed ewes were of a crossbred genotype that enhances both carcass characteristics and fertility traits. Use of sires that confer better conformation is an option but does not significantly boost prolificacy. Introduction of the ‘Inverdale’ fecundity gene could change this. On a flock basis in the Romney breed, mean ovulation is increased by 1.0 and litter size by 0.6 in adult ewes carrying a single copy of this gene (designated as FecXI because it is on the X chromosome; Davis et al. 1992). Carrier males transmit it to all of their female offspring, these being heterozygous carriers of the gene unless it also is maternally inherited. In the latter instance, young would be infertile the homozygous genotype confers an undesirable ‘streak ovary’ phenotype. Although a number of sheep breeds world-wide exhibit significant ‘single gene’ effects on ovulation and litter size (Montgomery et al. 2001), Scottish hill sheep breeds show no evidence of this. Consequently, all ewe lambs generated by crossing these hill ewes with a ram carrying the Inverdale gene should be heterozygous. To ascertain whether such animals exhibit enhanced fecundity, an on-farm study investigated ovulation incidence in cyclic ewe lambs born to Cheviot or Scottish Blackface ewes that had been bred to Texel rams carrying a single copy of the ‘Inverdale’ gene.

An investigation of the effects of <i>BMPR1B</i>, <i>BMP15</i>, and <i>GDF9</i> genes on litter size in Ramlıç and Dağlıç sheep

“…In this equation Y ij k indicates litter size, µ is the overall mean, H is the fixed effect of the herd, A is the random individual effect, b is the linear regression coefficient between the variants of the SNPs and litter size, and e ij k is random error N (0, σ 2 ). According to Aulchenko et al (2007) and Khatib (2015) this model takes SNPs as the covariate. Genotypes are coded as 0, 1, and 2 for none, a single copy, and double copies according to the presence of the rare allele.…”

“…The same gene causing prolificacy in heterozygous Romneys is called the Inverdale gene (FecX I ). The mutations of this gene identified in various breeds are called by different names such as FecX I , FecX H , FecX G , FecX B , FecX L , FecX R , FecX Gr , and FecX O (Alink et al, 2005;Davis, 2005;Davis et al, 1999). The GDF9 (FecG) gene on the fifth chromosome of sheep is also known to affect litter size and ovulation rate.…”