Genomewide association study for production and meat quality traits in Canchim beef cattle.

The commercial value of the bovine carcass is determined by a set of traits, such as weight, yield, back fat thickness, and marbling; therefore, the genetic improvement of growth, meat, and carcass quality traits is an important tool to add value to the supply chain. Genomewide association studies (GWAS) enable the identification of loci that control phenotypic expression of quantitative traits (QTL). Therefore, the objective of this work was to perform a GWAS to identify genomic regions and genes associated with growth, carcass traits, and meat quality in Canchim beef cattle. These traits were yearling weight (YW), rib eye area (REA), back fat thickness (BFT), and marbling (MARB). To increase sample size and marker density, genotype imputation was performed, and only markers imputed with greater than 95% accuracy were used. Genomewide association study was performed using a Bayesian approach, by the Bayes B statistical method, incorporating genotypes and phenotypes from 614 animals from both the Canchim breed and the MA genetic group (offspring of Charolais bulls and one-half Canchim + one-half Zebu cows). This investigation identified 1 and 4 genomic regions explaining 0.23 and 7.35% of the genetic variance for REA and YW, respectively. These regions harbor a total of 19 genes, 7 of which were classified for biological functions by functional analysis. Significant associations were not observed for BFT and MARB. The identification of QTL that had been previously described in the literature reinforces associations found in this study.

Identification and evaluation of polymorphisms in FABP3 and FABP4 in beef cattle.

Single nucleotide polymorphisms (SNPs) were screened in FABP3 and FABP4 by automatic sequencing of pools of DNA from crossbred animals whose phenotypes belonged to the upper and lower extremes for back fat and marbling, as well as of a pool of DNA from sires used for crossbreeding. Five SNPs were identified in FABP3 and another nine SNPs were identified in FAPB4. Of these, only one SNP had no previous registry in the SNAP database (dbSNP). Three polymorphisms were selected for further evaluation of their association with production traits using restriction fragment length polymorphism-PCR (RFLP-PCR) or real-time PCR genotyping. All 3 markers were in Hardy-Weinberg equilibrium at the 5% significance level for all 7 genetic groups analyzed. Significant association was observed between FABP3-G/A with rib eye area (P = 0.035) and the rib eye area/hot carcass weight ratio (P = 0.025) and between FABP4/TasI with marbling (P = 0.052) and meat texture (P = 0.053). No significant association was observed between the FABP4-G/C polymorphism and any of the observed traits. Previous association studies with allelic variants in these genes have shown mixed results, probably because of the small effect of the genes for these traits, which suggests that results should be replicated in other populations.