Muscle fiber type, postmortem metabolism, and meat quality of Nellore cattle with different post-weaning growth potential

Abstract Animal selection based on growth rate has received greater attention as a selection index. While many have evaluated the effect of growth rate on muscle characteristics and meat quality, few studies have attempted to evaluate how selection on growth rate alters muscle fiber characteristics and influences postmortem metabolism and subsequent meat quality. Therefore, the objective of this study was to evaluate muscle fiber type, postmortem metabolism and meat quality of Nellore cattle selected for different growth rates. Two-hundred and fifty non-castrated Nellore males differing in post-weaning growth potentials were used. Muscle from 10 high growth potential animals (EPDH) and 10 low growth potential animals (EPDL) were analyzed for muscle morphometric profile, postmortem metabolism, and meat quality. EPDH animals were heavier and had higher hot carcass weight and larger diameter and cross-sectional area of fast oxidative-glycolytic fibers, while EPDL animals had higher area percentage of slow oxidative fibers. Moreover, EPDH presented higher glycogen concentrations than EPDL cattle. Glucose concentrations were higher at 240, 720, and 1440 min postmortem, while G6P was higher from 30 to 1440 min postmortem in EPDL animals. Finally, EPDH animals produced less tender meat when compared to that of EPDL cattle. In conclusion, genetic selection based on growth potential is associate with a shift in fiber type towards a more glycolytic type of muscle that is associated with changes in meat tenderness.