Associação genômica ampla aplicada a características de adaptabilidade ao calor em bovinos da raça simental

Abstract

The world is currently concerned with global food production in the face of the uninterrupted population growth. In this scenario, Brazil presents itself as a promising producer to meet this demand, being one of the largest beef producer and exporter in the world. To further improve their production techniques and increase the meat supply, many producers adopt crossbreeding systems between Bos taurus indicus and Bos taurus taurus cattle, taking advantage of the best that this technique can bring in terms of productivity, such as heterosis and complementarity. One of the obstacles in this process is the tropical climate adaptability of animals originated in temperate climate. One of the breeds that used in Brazil is the Simmental. Genomic selection, made possible by GWAS, is one of the alternatives to alleviate this obstacle, allowing us to identify genetic variants associated with some phenotypic expression of traits of zootechnical interest.Thus, the objective in this study was to identify possible markers associated with genes that interfere in traits related to heat adaptability in Simmental cattle. There were used a total of 771 animals of the Simmental breed genotyped with a high-density SNP (Single Nucleotide Polymorphisms) chip, and 281 animals phenotyped for characteristics of: cowhide length (CP), cowhide thickness (EP), respiratory rate (FR), cowhide number (NP), cowhide temperature (TP) and rectal temperature (TR). After quality control, information on 646 animals and 113826 markers remained. The variance components and genetic parameters were estimated using a “single step” model (ssGBLUP), under Bayesian inference. GWAS analyzes were performed using the regression method corrected for polygenic random effects using the “GWAS” function from the rrBLUP package of the R statistical program. Through the GWAS study, 23 significant SNPs (P>0.04) were identified for CP; 19 significant SNPs (P>0.04) for EP; 10 significant SNPs (P>0.04) for FR; 78 significant SNPs (P>0.04) for NP; 26 significant SNPs (P>0.03) for TP; and 107 significant SNPs (P>0.04) for TR. The present genes that explain the percentage of additive genetic variance, observing the significance levels P>0.03 for TP and P>0.04 for the other traits, were identified by the Ensembl Biomart tool. Gene classification was performed by the DAVID 2021 program, which revealed significant ontological terms (P<0.05) with possible candidate genes associated with all characteristics. The results can trigger a better understanding of the biological mechanisms and genetic architecture of the revealed regions, as long as there are further studies that can validate and deepen the associations found, helping to obtain a greater prediction accuracy of the animals' genomic values. This fact can contribute to the evolution of the genetic improvement programs of the Simmental breed.