190 President Oral Presentation Pick: Transit affects metabolic profiles and antioxidant enzyme activity in the muscle of beef steers. (30th November 2020) - Deters, Erin L
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.