Session: Physiology and Endocrinology II

241 - Skeletal Muscle Mitochondrial Capacities Are Impacted by Breed and Temperament in Young Angus and Brahman Steers

Friday, July 16, 2021

2:30 PM – 2:45 PM EST

Location: Kentucky International Convention Center (KICC), M109 & 110

Presenting Author(s)

Chloey P. Guy

Graduate Assistant
Texas A&M University; Texas A&M AgriLife Research, College Station
College Station, Texas

PDF Slides and Audio

Author(s)

Lauren T. Wesolowski

Graduate Assistant
Texas A&M University; Texas A&M AgriLife Research
College Station, Texas
Audrey L. Earnhardt, MS

PhD Student
Texas A&M University; Texas A&M AgriLife Research, College Station
College Station, Texas
DL

Dustin Law

Texas A&M AgriLife Research, Overton
Overton, Texas
DN

Don A. Neuendorff, M.S.

Research Associate
Texas A&M AgriLife Research, Overton
Overton, Texas
CL

Charles R. Long, Ph.D.

Resident Director
Texas A&M AgriLife Research, Overton
Overton, Texas
GP

George A. Perry

Texas A&M AgriLife Research, Overton
Overton, Texas
RR

Ron D. Randel, Ph.D.

Professor
Texas A&M AgriLife Research, Overton
Overton, Texas
TW

Thomas H. Welsh, Jr.

Professor
Texas A&M University; Texas A&M AgriLife Research, College Station
College Station, Texas
Sarah H. White-Springer, PhD

Assistant Professor
Texas A&M University; Texas A&M AgriLife Research, College Station
College Station, Texas

Temperament impacts skeletal muscle mitochondria in Brahman heifers, but this has not been investigated in steers or between cattle breeds. We hypothesized mitochondrial measures would be greater in Angus than Brahman, temperamental than calm steers, and the trapezius (TRAP) than the longissimus thoracis (LT) muscle. Samples from calm (n = 13 per breed), intermediate (n = 12 per breed), and temperamental (n=13 per breed) Angus and Brahman steers (mean±SD 10.0±0.8 mo) were evaluated for mitochondrial enzyme activities via colorimetry. Calm and temperamental LT samples were evaluated for oxidative phosphorylation (P) and electron transfer (E) capacities by high-resolution respirometry. Data were analyzed using linear models with fixed effects of breed, muscle, temperament, and all interactions. Brahman tended to have greater mitochondrial volume density (citrate synthase activity; CS) than Angus (P = 0.08), while intrinsic (relative to CS) mitochondrial function (cytochrome c oxidase activity) was greater in Angus than Brahman (P = 0.001) and greater in TRAP than LT (P = 0.008). Angus exhibited greater integrative (per mg tissue) and intrinsic P with complex I (P_CI), P with complexes I+II (P_CI+II), maximum noncoupled E, and E with complex II (E_CII; P ≤ 0.04) and tended to have greater intrinsic leak (P = 0.1) than Brahman. Contribution of P<sub>CI to total E was greater in Angus than Brahman (P = 0.01), while contribution of E_CII to total E was greater in Brahman than Angus (P = 0.05). A trend for the interaction of breed and temperament (P = 0.07) indicated calm Angus had the greatest intrinsic E_CII (P ≤ 0.03) while intrinsic E_CII was similar between temperamental Angus and calm and temperamental Brahman. Integrative P<sub>CI+II and E_CII, and the contribution of P<sub>CI and P<sub>CI+II to overall E tended to be greater in temperamental than calm steers (P ≤ 0.09), while intrinsic E_CII tended to be greater in calm than temperamental steers (P = 0.07). The impact of these mitochondrial differences on meat quality measures remains to be determined.