Reproductive traits are essential in dairy cattle breeding, and improving body conformation is considered beneficial for reproductive performance. This study systematically analyzed the genetic relationships between six key conformation traits—stature (ST), body depth (BD), loin strength (LS), rump angle (RA), rump width (RW), bone quality (BQ)—and reproductive performance in 1631 Jersey cattle from China. Heritability estimates for conformation traits ranged from 0.05 to 0.62. We identified significant phenotypic and genetic correlations between conformation and reproductive traits, and regression analyses confirmed the predictive value of conformation traits for reproductive outcomes. Genome-wide association studies detected 24 significant SNPs associated with ST, RW, RA, and BQ. Subsequent bioinformatics analysis revealed seven candidate genes (AZIN1, OR2H1, HS6ST3, ERCC4, KCNH5, KRT19, KRT35) involved in embryonic development and estrous cycle regulation. Notably, incorporating six SNPs, which are linked to these candidate genes, into genomic prediction models significantly improved the accuracy for predicting Age at First Calving (AFC) and Gestation Length (GL). These results elucidate the shared genetic basis of conformation and reproduction, providing theoretical support for using conformation traits in marker-assisted selection to enhance reproductive efficiency in Jersey cattle.

This study characterized the genetic basis of reproductive and calving traits in Jersey cattle at different physiological stages and identified potential candidate genes. After quality control, 2716 records were available for heifer reproductive traits, 2707 for multiparous cow reproductive traits, and 5423 calving records for calving ease (CE) and calf birth weight (CBW). CE and CBW were analyzed from the maternal perspective, with records assigned to the corresponding dams. Genetic parameters were estimated using AI-REML in DMU with animal, repeatability, and bivariate models. Genome-wide association analyses were performed using a mixed linear model based on 1,660,477 SNPs from 1578 genotyped Jersey cattle. Heritability estimates for age at first service (AFS) and age at first calving (AFC) were 0.416 and 0.380, respectively, whereas estimates for reproductive traits in multiparous cows were generally low (0.072–0.154). Calving interval (CI) and days open (DO) showed a strong positive genetic correlation (0.781). GWAS identified five significant loci associated with AFC, number of services per conception in heifers, CI, and dam-associated genetic variation in CE. Candidate genes included PIK3C2G, DGKI, ABCC1, CCDC85A, CRMP1, EVC, and EVC2. Exploratory KEGG enrichment suggested potential involvement of phosphatidylinositol signaling, Hedgehog signaling, ABC transporters, and inositol phosphate metabolism. Overall, reproductive traits showed distinct genetic characteristics between heifers and multiparous cows, and AFS and AFC exhibited relatively greater potential for genetic improvement. The identified genomic regions provide preliminary candidates for further validation and potential future application in genomic breeding.