Abstract

Fertility traits are core functional traits in dairy cattle, yet their low heritability makes traditional phenotypic selection inefficient. Weighted single-step GWAS (WssGWAS) improves detection power by integrating pedigree, phenotype, and genotype data. This study aimed to estimate genetic parameters and identify genomic regions associated with eight fertility traits in Chinese Holstein cattle using pedigree, phenotype, and genotype data. Genetic parameters were estimated via pedigree-based BLUP (PBLUP) and ssGBLUP, and a WssGWAS was performed to detect QTL. A total of 23,771 cattle were genotyped using liquid-phase chips and 150 K chips; after imputation and quality control, 13,690 individuals and 103,262 SNPs were retained. The eight traits comprised heifer traits (AFS, AFC, NS_H, and IFL_H) and cow traits (ICF, CI, NS_C, and IFL_C). The findings indicate that while most fertility traits exhibit low heritability (ranging from 0.024 to 0.085), AFS displays high heritability (0.390). WssGWAS identified 162 QTL intervals and 645 candidate genes, including OVOS2, PMEPA1, TEPP, and the RAG family, which are closely associated with reproductive function. These findings provide a foundation for future research into the genetic mechanisms of fertility and support improved genomic predictions in Chinese Holstein cattle.

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