Sex-specific effects of guanosine monophosphate synthase and steroid receptor coactivator gene polymorphisms on cashmere fineness and production traits in Liaoning Cashmere goats

Background and Aim: The Liaoning Cashmere goat (LCG) is a dual-purpose breed of major economic importance in China, valued for its high cashmere yield and meat quality. Cashmere fineness (CF) remains a primary target for genetic improvement because fiber diameter directly determines textile value and market price. This study examined the sex-specific effects of single-nucleotide polymorphisms in the guanosine monophosphate synthase (GMPS) and steroid receptor coactivator (SRC) genes on CF and a broad spectrum of production traits to identify functional markers for marker-assisted selection. Materials and Methods: A total of 1,160 healthy LCGs (89 bucks and 1,071 does, 2–4 years of age) from the same nucleus herd were included. The C31799T locus in GMPS and the C34197G locus in SRC were genotyped by polymerase chain reaction (PCR) amplification followed by bidirectional Sanger sequencing. Genotype–trait associations were tested using general linear mixed models, with genotype, sex, and age as fixed effects, and pedigree information incorporated to control for relatedness. Haplotype phases were inferred separately for each sex with the SHEsis platform. Phenotypes recorded comprised cashmere production traits (fineness, length, yield), body size measurements, slaughter performance, meat quality attributes, milk composition, and lambing rate. Data normality, homoscedasticity, and multicollinearity were verified prior to analysis; statistical significance was declared at p < 0.05. Results: The TT genotype at the GMPS C31799T locus and the CG genotype at the SRC C34197G locus were significantly associated with finer cashmere fibers (p < 0.05). Sex-stratified analyses showed that the GMPS TT genotype conferred superior CF in does (p < 0.01) and longer staple length in both sexes (p < 0.01), whereas the SRC CG genotype improved fineness specifically in does (p < 0.01). Haplotype analysis identified CCCC as the optimal combination for finer cashmere in bucks and TTGG in does. Pleiotropic effects were evident: the GMPS CC genotype favored larger body dimensions, the GMPS TT genotype enhanced carcass traits in bucks, and the SRC CG genotype improved lactation performance. CF exhibited positive correlations with cashmere yield (bucks: r = 0.412; does: r = 0.384; p < 0.01) and negative associations with several slaughter traits. Path and stepwise regression analyses clarified direct and indirect effects, underscoring sex-dependent genetic trade-offs between fiber quality and meat production. Conclusion: This is the first study to establish GMPS and SRC as key candidate genes influencing CF in goats. The identified superior genotypes and haplotypes provide sex-specific molecular markers that can be immediately deployed in marker-assisted selection programs to accelerate genetic gains in cashmere quality while safeguarding meat production potential in LCG breeding. Validation in independent populations will further strengthen their utility for precision breeding. Keywords: cashmere fineness, Cashmere goat, Cashmere production traits, cashmere yield, GMPS gene, Liaoning Cashmere goat, marker-assisted selection, SRC gene.