Study of the influence of genes related to muscle oxidative processes on beef color.

The biochemical bases of meat color are determined by the concentration and redox state of myoglobin, hemoglobin, cytochromes, and other pigments. Post-mortem depletion of cellular oxygen results in oxidative stresses that consume NADH and affects reducing activity, while enzymatic detoxification influences the cellular oxidative processes, both affecting meat color. The aim of this work was to study the influence of several genes related to cellular oxidative processes that could affect CIELAB meat color parameters. The study was performed in steers that received a grass-based diet combined with grain, hays and silages. Results suggest a possible link between colorimetric parameters (a*, b* and chroma) and SNPs in the GSTP1 gene (P<0.05). Although the influence of the enzymes, encoded by GSTP1 gene, on meat color has been proposed previously at biochemical level and protein expression level, further association studies in different populations and functional studies of proteins are needed to confirm the genetic determination of that gene on meat color.

Genetic and management factors affecting beef quality in grazing Hereford steers.

Attributes contributing to differences in beef quality of 206 Hereford steers finished on pasture were assessed. Beef quality traits evaluated were: Warner-Bratzler meat tenderness and muscle and fat color at one and seven days after slaughter and trained sensory panel traits (tenderness, juiciness, flavor, and marbling) at seven days. Molecular markers were CAPN1 316 and an SNP in exon 2 on the leptin gene (E2FB). Average daily live weight gain, ultrasound monthly backfat thickness gain and rib-eye area gain were estimated. Molecular markers effects on meat quality traits were analyzed by mixed models. Association of meat quality with post weaning growth traits was analyzed by canonical correlations. Muscle color and marbling were affected by CAPN1 316 and E2FB and Warner-Bratzler meat tenderness by the former. The results confirm that marker assisted selection for tenderness is advisable only when beef aging is a common practice. The most important sources of variation in tenderness and color of meat remained unaccounted for.

Association of a novel polymorphism in the bovine PPARGC1A gene with growth, slaughter and meat quality traits in Brangus steers.

The PPARGC1A gene (peroxysome proliferator-activated receptor-gamma coactivator 1alpha gene) controls muscle fiber type and brown adipocyte differentiation; therefore, it is a candidate gene for beef quality traits (tenderness and fat content). Two SNPs (Single Nucleotide Polymorphisms) were identified within exon 8 by multiple alignment of DNA sequences obtained from 24 bulls: a transition G/A (SNP 1181) and a transversion A/T (SNP 1299). The SNP 1181 is a novel SNP, corresponding to a non-conservative substitution (AGT/AAT) that could be the cause of amino acid substitution ((364)Serine/(364)Asparagine). A Mismatch PCR method was designed to determine genotypes of 73 bulls and 268 steers for SNP 1181. Growth, slaughter and meat quality information were available for the group of steers. Allele A of SNP 1181 was not found in Angus. In 243 steers, no significant differences (P > 0.05) were found for either final live body weight, gain in backfat thickness in Spring, kidney fat weight, kidney fat percentage, Warner-Bratzler shear force at 7 days postmortem, intramuscular fat percentage or meat colour between genotype GG and AG. This SNP could be included in breed composition and population admixture analyses because there are marked differences in allelic frequencies between Bos taurus and Bos indicus breeds.

Effect of leptin gene polymorphisms on growth, slaughter and meat quality traits of grazing Brangus steers.

Leptin is a hormone that affects the regulation of feed intake, energy balance and body composition in mammals. Several polymorphisms in the bovine leptin gene have been associated with phenotypic variance of these traits. We evaluated two known single nucleotide polymorphisms (SNPs) in the leptin gene of 253 grazing Brangus steers. Brangus is a 5/8 Angus-3/8 Brahman composite. Data were collected during two consecutive growth/fattening cycles from two farms in southeast Buenos Aires province, Argentina. One of the markers is in the promoter region of the gene (SNP1) and the other is a non-synonymous polymorphism in exon 2 (SNP2). The traits that we evaluated were live weight gain in the spring, gain in backfat thickness in the spring, final live weight, final ultrasound backfat thickness, final ultrasound rib eye area, carcass weight and length, carcass yield, kidney fat, kidney fat percentage, backfat thickness, rib eye area, and intramuscular fat percentage. Both markers affected some meat traits; though the only significant associations were of SNP1 with ultrasound rib eye area and of SNP2 with carcass yield and backfat thickness. Under the same conditions as in the present study, leptin markers could be of help only as part of a larger genotyping panel including other relevant genes.