Multivariate Single-Step GWAS Reveals Pleiotropic Genomic Regions and Candidate Genes Associated with Male Scrotal Circumference and Female Fertility Traits in Retinta Beef Cattle

Fertility is key for calf production. Direct selection for female fertility under field conditions is hindered by low accuracy and selection response. An alternative widely implemented is selection for scrotal circumference (SC), genetically correlated with daughter fertility. This study performed a genome-wide association study (GWAS) to identify genomic regions and candidate loci linked to SC and female fertility in Retinta cattle. A multivariate ssGBLUP was applied using SC records from 1061 bulls, fertility-related traits from 59,254 females and genotypes from 1230 animals using the Axiom™ Bovine Genotyping v3 Array (65k). The ssGWAS revealed 23 1-Mb windows explaining >1% of additive genetic variance for SC, one on chromosome 2 and 22 on chromosome 3. Within these windows, 198 regions spanning 118 protein-coding genes and 80 RNA genes were identified. Several genes, including <i>GSTM3</i>, <i>SPATA1</i>, <i>HFM1</i>, and <i>MSH4</i>, were previously associated with male fertility. Six regions overlapped across male and female traits, containing two protein-coding genes (<i>THSD7B</i> and ENSBTAG00000021755). Identification of genomic markers linked to both female fertility and male SC enables selection of superior animals, improving reproductive efficiency and advancing knowledge of the genomic basis of male-female fertility relationships.