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Grazing steers from Angus and Hereford breeds, their cross-breeds and a three-way cross-breed (Limousin × Angus-Hereford) were measured for growth, carcass and meat quality traits. Breed effects were studied, and the association of SNPs with fat deposition and fatty acid (FA) composition (leptin, melanocortin-4 receptor, stearoyl-CoA desaturase, FA synthase and thyroglobulin) was tested. Limousin cross-breed showed the greatest final body weight, ultrasound rib eye area, dressing percentage, carcass and leg length, and the lowest backfat thickness and intramuscular fat content. Genetic groups had similar pH, shear force, cooking loss, L* and b* and n-6:n-3 ratio. Meat from 1/2-Angus presented greater a* than Limousin cross-breed. Whereas Angus had the highest total SFA content, Hereford had the lowest total SFA and the highest total MUFA. Limousin cross-breed had greater content of several individual PUFAs, total PUFA, n-6 and n-3 FA than Angus and 1/2-Angus. Leptin and FA synthase were associated with some FAs, supporting their influence over fat metabolism for grazing animals., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)