190 President Oral Presentation Pick: Transit affects metabolic profiles and antioxidant enzyme activity in the muscle of beef steers

Abstract

Abstract This study sought to elucidate the effects of road transportation on muscle metabolites and antioxidant defense of beef steers. Thirty-six Angus-cross steers (324 ± 36 kg) from a single source were stratified by body weight, then randomly assigned to pens equipped with GrowSafe bunks (6 steers/pen) and treatments (12 steers/treatment): CON = no transit, ad libitum feed and water; DEPR = no transit, deprived of feed and water for 18 h; or TRANS = trucked (1,790 km) with no feed and water for 18 h. Treatments were initiated on d 0 and terminated ~18 h later. Muscle (longissimus dorsi) samples collected from all steers on d -4, 1, and 3 were analyzed for superoxide dismutase (SOD) activity; while d 1 and 3 samples were utilized for complete metabolite analysis via gas chromatography-mass spectrometry. Antioxidant data were analyzed as a completely randomized design using ProcMixed of SAS 9.4 (experimental unit = steer, fixed effect = treatment). Metabolomics data were analyzed with MetaboAnalyst 4.0 where area under the curve (AUC) was used to identify metabolites as potential biomarkers. On d 1, total SOD activity was greatest for TRANS (P = 0.02) driven by a tendency for greater Mn-SOD activity (P = 0.10) and greater CuZn-SOD activity (P = 0.02). On d 3, Mn-SOD activity tended to be least for TRANS (P = 0.07). Metabolites of the pentose phosphate pathway (gluconic acid and D-ribose) were identified as potential biomarkers in TRANS muscle on d 3 when compared to CON (AUC ≥ 0.85) or DEPR (AUC ≥ 0.75). Under conditions of oxidative stress, glucose will be diverted from glycolysis to the pentose phosphate pathway to produce reducing equivalents. Alterations in muscle metabolic profiles coupled with lesser Mn-SOD activity 48 h post-transit may indicate residual oxidative stress, which could negatively affect feedlot performance.