Genetic and genomic analyses of testicular hypoplasia in Nellore cattle

Author(s)

Neves, Haroldo H. R. ^[1] ; Vargas, Giovana ^[2] ; Brito, Luiz F. ^[3] ; Schenkel, Flavio S. ^[4] ; Albuquerque, Lucia G. ^{[2, 5]} ; Carvalheiro, Roberto ^{[5, 1]}

Affiliation

^[1] GenSys Associated Consultants, Porto Alegre, RS - Brazil

^[2] Sao Paulo State Univ UNESP, Sch Agr & Vet Sci, Dept Anim Sci, Jaboticabal, SP - Brazil

^[3] Purdue Univ, Dept Anim Sci, W Lafayette, IN 47907 - USA

^[4] Univ Guelph, Dept Anim Biosci, CGIL, Guelph, ON - Canada

^[5] Cnpq, Natl Council Sci & Technol Dev, Brasilia, DF - Brazil

• Document type: Journal article
• Source: PLoS One; v. 14, n. 1 JAN 24 2019.
• Web of Science Citations: 0

Abstract

Reproductive performance is a key indicator of the long-term sustainability of any livestock production system. Testicular hypoplasia (TH) is a morphological and functional reproductive disorder that affects bulls around the world and consequently causes major economic losses due to reduced fertility rates. Despite the improvements in management practices to enhance performance of affected animals, the use of hypoplastic animals for reproduction might contribute to expand the prevalence of this disorder. The aim of this study was to identify genomic regions that are associated with TH in Nellore cattle by performing a genome-wide association study (GWAS) and functional analyses. Phenotypic and pedigree data from 47,563 animals and genotypes (500,689 Single Nucleotide Polymorphism, SNPs) from 265 sires were used in this study. TH was evaluated as a binary trait measured at 18 months of age. The estimated breeding values (EBVs) were calculated by fitting a single-trait threshold animal model using a Bayesian approach. The SNP effects were estimated using the Bayes C method and de-regressed EBVs for TH as the response variable (pseudo-phenotype). The top-15 ranking windows (5-adjacent SNPs) that explained the highest proportion of variance were identified for further functional and biological network analyses. The posterior mean (95% highest posterior density) of the heritability for TH was 0.16 (0.08; 0.23). The most important genomic windows were located on BTA1, BTA3, BTA4, BTA5, BTA9, BTA22, BTA23, and BTA25. These windows explained together 22.69% of the total additive genetic variance for TH. Strong candidate genes associated with metabolism and synthesis of steroids, cell survival, spermatogenesis process and sperm motility were identified, which might play an important role in the expression of TH. Our findings contribute to a better biological understanding of TH and future characterization of causal variants might enable improved genomic prediction of this trait in beef cattle. (AU)

• FAPESP's process: 17/10630-2 - Genetic aspects of meat production quality, efficiency and sustainability in Nelore breed animals
• Grantee: Lucia Galvão de Albuquerque
• Support Opportunities: Research Projects - Thematic Grants