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

## TL;DR

This study identifies genes linked to male scrotal circumference and female fertility in Retinta cattle, revealing shared genetic regions that could improve breeding strategies.

## Contribution

The study discovers pleiotropic genomic regions and candidate genes for male and female fertility traits in a specific cattle breed.

## Key findings

- 23 genomic regions on chromosomes 2 and 3 were found to explain over 1% of genetic variance for scrotal circumference.
- 198 regions spanning 118 protein-coding and 80 RNA genes were identified, including genes previously linked to male fertility.
- Six overlapping regions were found between male and female traits, containing genes like THSD7B and ENSBTAG00000021755.

## Abstract

Reproduction plays a crucial role in the long-term sustainability of livestock, particularly in extensive production systems. However, reproductive traits typically exhibit low heritability, mainly due to the general lack of objective performance control criteria related to fertility in breeding females, and the fact that these traits are subject to numerous environmental effects that are difficult to quantify. This means that, in many beef cattle breeds, an indirect selection criterion is being used, such as the male’s scrotal circumference, because it is considered to be associated with the fertility of his daughters. This would imply the existence of genes with pleiotropic effects in both sexes. To better understand the genetic architecture underlying these traits, a genome-wide association study was conducted for scrotal circumference (SC) and several female fertility traits within the Retinta cattle breed. Genes previously reported in cattle breeds for SC and female fertility traits were identified in this study. Two of these main genes were detected in the GWAS of the bull’s scrotal circumference and parameters related to cow fertility.

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 GSTM3, SPATA1, HFM1, and MSH4, were previously associated with male fertility. Six regions overlapped across male and female traits, containing two protein-coding genes (THSD7B 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.