Differing Mitochondrial Capacity in Two Separate Skeletal Muscles from Calm and Temperamental Brahman Heifers.

White, S H; Latham, C M; Long, C R; Randel, R D; Welsh, T H

Muscle mitochondrial capacity has been linked to beef tenderness. Additionally, temperamental cattle often have poorer meat product quality. If mitochondrial capacity in a muscle that is of low commercial value can be used to predict which cattle may have enhanced meat quality, the producer may realize an economic advantage. To test the hypothesis that mitochondrial number and function would be greatest in temperamental animals, and would be higher in the longissimus dorsi (LD) than the trapezius, samples from both muscles were collected from calm (n=6) and temperamental (n=6) 8-mo-old Brahman heifers using a 14-gauge tissue collection needle. Heifer temperament was determined at weaning using pen score and exit velocity. Colorimetric analysis for mitochondrial density (via citrate synthase, CS, activity) and function (via cytochrome c oxidase, COX, activity) was performed on all samples, and mitochondrial capacity was measured utilizing high-resolution respirometry. Data were analyzed using the MIXED procedure of SAS (9.4). Relative to mg tissue (integrative), the LD from temperamental heifers had greater mitochondrial number (CS activity; PCI II) was also higher in the LD of temperamental compared to calm heifers (P=0.012), but all other integrative capacities were unaffected by temperament and muscle. While also unaffected by temperament, intrinsic (relative to CS activity) mitochondrial state 3 oxidative phosphorylation capacity with complex I substrates (PCI; 6.81 ± 0.48 and 4.31 ± 048 pmol/ s*U CS for trapezius and LD, respectively; P=0.002), PCI with complex II substrates (PCI II; 11.33 ± 0.79 and 6.74 ± 0.79; P=0.0006), electron transport system capacity (ECI II; 14.06 ± 0.87 and 7.90 ± 0.87; PCI compared to the trapezius (0.54 ± 0.02 and 0.49 ± 0.01 for LD and trapezius, respectively; P=0.057), indicating greater contribution of CI to energy production in the LD. Temperament was not associated with most measures of mitochondrial function in this study. Future research will delineate if these differences in mitochondria persist throughout the animal's lifetime, or if they relate to product quality.

MUSCLE mitochondria; TEMPERAMENT; BEEF quality

Journal of Animal Science, 2018, Vol 96, p46

0021-8812

Academic Journal

10.1093/jas/sky027.088