Estimation of Genetic Parameters and GWAS on Water Efficiency Traits in the Senepol Cattle

The need for producing in environmentally resilient system drives new research to achieve sustainable beef production. Water footprint of the beef supply chain is a concern that must be addressed, aiming to improve water use within the production chain. One approach is genetic selection of beef cattle for water efficiency. However, it is essential to understand the genetic architecture and mechanisms involved in the expression of this phenotype to choose the best selection criteria. Thus, our study aimed to estimate genetic parameters for water efficiency traits, conduct a genome-wide association study (GWAS) and identify the genetic networks and biological processes involved. A population of 1762 purebred Senepol cattle was phenotyped for the following water efficiency traits: water intake (WI), gross water efficiency (GWE), water conversion ratio (WCR), residual water intake based on average daily gain (RWI_ADG) and residual water intake based on dry matter intake (RWI_DMI). A subset of 1342 animals was genotyped using GGP Bovine 50 K SNP Chip with (734 animals) or 100 K (508 animals), and imputation from 50 K to 100 K was performed with Beagle software. The heritability estimates were 0.36 ± 0.06, 0.26 ± 0.05, 0.22 ± 0.05, 0.24 ± 0.05 and 0.20 ± 0.05 for WI, GWE, WCR, RWI_ADG and RWI_DMI, respectively. Unlike the raw measures of WI, the phenotypic correlations between average daily gain (ADG) and the residuals (RWI_DMI and RWI_ADG) were zero. All water efficiency traits were moderately to highly correlated with each other. GWAS were used to estimate the effect of 79,860 single nucleotide polymorphisms (SNPs), and significant SNPs were only observed for WCR. Enrichment analysis of genes in the significant regions revealed the involvement of different biological processes, such as saliva production, water transport, renal system and immune system. Genetic selection of Senepol cattle for water efficiency traits is feasible and can reduce water requirements for meat production. Water efficiency measures are polygenic traits, and different biological processes act simultaneously on the expression of related phenotypes.