Abstract
Bos taurus indicus temperament is variable and affects beef tenderization. Our objective was to investigate temperament and performance of non–castrated Nellore and identify groups based on Longissimus lumborum (LL) pH decline as well as beef characteristics produced by those groups. We investigated 94 animals with a subset of carcasses (n = 24) selected based on LL pH at 24 h postmortem (pm) to represent two groups: resistant to pH decline (> 5.8 called pH–Res; n = 10) and normal (< 5.7 called pH–Nor; n = 14). Steaks were fabricated from the LL muscle and randomly assigned to aging (2, 7, 14, and 21 days). Sarcomere length, cooking loss, myofibrillar fragmentation index (MFI), and Warner–Bratzler shear force (WBSF) were determined. Data on temperament were investigated in a multivariate approach, while beef data were compared between groups using the analysis of variance. Rectal temperature at the beginning of the finishing phase and total weight gain were greater and related to animals in the pH–Res group (p < 0.01 and p = 0.03, respectively). Temperature and pH decline curves, sarcomere length, and cooking loss revealed that pH–Res produced beef with lower quality compared to the pH–Nor group. Results for MFI and WBSF did not show differences between groups within each time pm; however, overall steaks from pH–Res were tougher (p = 0.06). Incidence of LL pH between 5.8 and 5.9 at 24 h pm did not compromise the tenderization rate or extension; however, it affected the water holding capacity in this population of Nellore cattle.
Highlights
Bos taurus indicus subspecies has greater ability to cope with tropical conditions compared to non–adapted Bos taurus taurus, but at the expense of reduced beef quality (Wheeler et al, 1996)
Temperature and pH decline curves, sarcomere length, and cooking loss revealed that pH–Res produced beef with lower quality compared to the pH–Nor group
This average index considered chute score (CS) and exit velocity (EV) measured in the first handling, after animals were transferred from pasture to feedlot and adapted to diets
Summary
Bos taurus indicus subspecies has greater ability to cope with tropical conditions compared to non–adapted Bos taurus taurus, but at the expense of reduced beef quality (Wheeler et al, 1996). Meat toughness in Nellore cattle is associated to greater calpastatin activity (Whipple et al, 1990); animal behavior can influence meat tenderness. More excitable steers are associated to greater sympathetic tonus and consequent greater stimulation of hypothalamic–pituitary–adrenal axis resulting in beef with reduced tenderness (Coutinho et al, 2017). Excitable animals can have reduced concentration of muscle glycogen at slaughter, which limits adenosine triphosphate (ATP) levels postmortem (pm) and hindering the pH decline. The pH rates and temperature decline have a significant effect on proteases activation and beef quality (Hwang and Thompson, 2001)
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