Bovine gene polymorphisms related to fat deposition and meat tenderness

Leptin, thyroglobulin and diacylglycerol O-acyltransferase play important roles in fat metabolism. Fat deposition has an influence on meat quality and consumers' choice. The aim of this study was to determine allele and genotype frequencies of polymorphisms of the bovine genes, which encode leptin (LEP), thyroglobulin (TG) and diacylglycerol O-acyltransferase (DGAT1). A further objective was to establish the effects of these polymorphisms on meat characteristics. We genotyped 147 animals belonging to the Nelore (Bos indicus), Canchim (5/8 Bos taurus + 3/8 Bos indicus), Rubia Gallega X Nelore (1/2 Bos taurus + 1/2 Bos indicus), Brangus Three-way cross (9/16 Bos taurus + 7/16 Bos indicus) and Braunvieh Three-way cross (3/4 Bos taurus + 1/4 Bos indicus) breeds. Backfat thickness, total lipids, marbling score, ribeye area and shear force were fitted, using the General Linear Model (GLM) procedure of the SAS software. The least square means of genotypes and genetic groups were compared using Tukey's test. Allele frequencies vary among the genetic groups, depending on Bos indicus versus Bos taurus influence. The LEP polymorphism segregates in pure Bos indicus Nelore animals, which is a new finding. The T allele of TG is fixed in Nelore, and DGAT1 segregates in all groups, but the frequency of allele A is lower in Nelore animals. The results showed no association between the genotypes and traits studied, but a genetic group effect on these traits was found. So, the genetic background remains relevant for fat deposition and meat tenderness, but the gene markers developed for Bos taurus may be insufficient for Bos indicus

Genome-Wide Association Study of Meat Quality Traits in Nellore Cattle

<div><p>The objective of this study was to identify genomic regions that are associated with meat quality traits in the Nellore breed. Nellore steers were finished in feedlots and slaughtered at a commercial slaughterhouse. This analysis included 1,822 phenotypic records of tenderness and 1,873 marbling records. After quality control, 1,630 animals genotyped for tenderness, 1,633 animals genotyped for marbling, and 369,722 SNPs remained. The results are reported as the proportion of variance explained by windows of 150 adjacent SNPs. Only windows with largest effects were considered. The genomic regions were located on chromosomes 5, 15, 16 and 25 for marbling and on chromosomes 5, 7, 10, 14 and 21 for tenderness. These windows explained 3,89% and 3,80% of the additive genetic variance for marbling and tenderness, respectively. The genes associated with the traits are related to growth, muscle development and lipid metabolism. The study of these genes in Nellore cattle is the first step in the identification of causal mutations that will contribute to the genetic evaluation of the breed.</p></div

Descriptive statistics and heritability (h²) estimates of meat quality traits in Nellore cattle.

<p>Descriptive statistics and heritability (h²) estimates of meat quality traits in Nellore cattle.</p

Chromosome (Chr), location, identification of genes and proportion of variance (VAR) explained by windows with largest effects on tenderness^a.

<p>Chromosome (Chr), location, identification of genes and proportion of variance (VAR) explained by windows with largest effects on tenderness<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157845#t003fn001" target="_blank">^a</a>.</p

Manhattan plot of additive genetic variance explained by windows of 150 adjacent SNPs for Marbling.

<p>Manhattan plot of additive genetic variance explained by windows of 150 adjacent SNPs for Marbling.</p

Chromosome (Chr), location, identification of genes and proportion of variance (VAR) explained by windows with largest effects on marbling^a.

<p>Chromosome (Chr), location, identification of genes and proportion of variance (VAR) explained by windows with largest effects on marbling<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157845#t002fn001" target="_blank">^a</a>.</p