277 Live Animal Mitochondrial Markers During the Feedlot Phase are Related to Meat Quality in Angus but not Brahman Steers

Abstract Mitochondrial activity correlates with meat product quality post-harvest but little is known about the relationships between live animal mitochondria and at slaughter. To test hypothesis that skeletal muscle mitochondrial markers would be correlated longissimus Warner-Bratzler shear force (WBSF) post-harvest, thoracis (LT) trapezius (TRAP) samples were collected from Brahman Angus steers (n = 36 per breed) during grazing growth phase (GP) after 120 days on feed (FP). Samples analyzed for enzyme activities via colorimetry oxidative phosphorylation (P) electron transfer (E) capacities high-resolution respirometry. Relationships variables WBSF determined using PROC CORR in SAS (v9.4). Within GP, LT volume density as measured by citrate synthase (CS) was positively (P=0.009). In FP, intrinsic (relative to CS) P complex I (PCI) maximal E complexes II (ECI+II) (P≤0.05), while contribution of (PCI+II) (flux control ratio, FCRPCI+II) negatively (P=0.03). Also TRAP integrative mg tissue) PCI, PCI+II, ECI+II FCRPCI (P≤0.02), FCR through only (FCRECII) (P=0.007). Brahman, no either GP or FP. Post-harvest tenderness related when evaluated close slaughter not steers.