The polymorphism in the gonadotropin-releasing hormone receptor (GnRHR) gene was detected by PCR single-strand conformational (PCR-SSCP) and DNA sequencing methods in 224 Boer goats. Two single nucleotide polymorphisms (SNPs), G891T and G757A, were found in the exon I of the goat GnRHR gene and their associations with litter size in Boer goats were evaluated. Association analysis showed that G891T and G757A had significant effects on litter size. In locus G891T, individuals with GT genotype had significantly larger litter sizes compared to GG genotype in the first and third parity. In locus G757A, ewes with GG genotype had significantly higher litter sizes than those of GA in the fourth parity. The present study primarily revealed an association between allele T at 891 locus of the GnRHR gene and high litter size in the first and third parity in Boer goats. These results provide evidence that the GnRHR gene may be significantly correlated with a high prolificacy in goats.

Two active mutations (A 781 G and A 1575 G) in growth hormone (GH) gene, and their associations with litter size (LS), were investigated in both a high prolificacy (Matou, n = 182) and a low prolificacy breed (Boer, n = 352) by using the PCR-RFLP method. Superovulation experiments were designed in 57 dams, in order to evaluate the effect of different genotypes of the GH gene on superovulation response. Two genotypes (AA and AB, CC and CD) in each mutation were detected in these two goat breeds. Neither BB nor DD homozygous genotypes were observed. The genotypic frequencies of AB and CC were significantly higher than those of AA and CD. In the third parity, Matou dams with AB or CC genotypes had significantly larger litter sizes than those with AA and CD (p < 0.05). On combining the two loci, both Matou and Boer dams with ABCD genotype had the largest litter sizes when compared to the other genotypes (p < 0.05). When undergoing like superovulation treatments, a significantly higher number of corpora lutea and ova, with a lower incidence of ovarian cysts, were harvested in the AB and CC genotypes than in AA and CD. These results show that the two loci of GH gene are highly associated with abundant prolificacy and superovulation response in goat breeds.