PSV-17 The Interaction Between Heat Stress and Zearalenone Toxicity in Porcine Skeletal Muscle Free

Heat stress (HS) and Zearalenone (Zen) exposure negatively impact growth, production efficiency, animal welfare, and both can be lethal. Zearalenone, a mycotoxin, can contaminate a variety of feedstuffs. As both HS and Zen independently can cause oxidative stress, we hypothesized that concomitant exposure to HS and Zen would cause oxidative stress in pig skeletal muscle more than either agent alone. Prepubertal gilts (n = 26) were fed placebo or Zen (40 ug/kg) twice daily and exposed to thermoneutral conditions (TN; 21.0 °C) or a 12 h diurnal HS challenge (simulated night - 32.2 °C; simulated day - 35.0 °C) for 7 d. Immediately following the environmental challenge, pigs were euthanized and the oxidative (STR) portion of the semitendinosus muscle was collected. Heat stress increased rectal temperature following the simulated nighttime (TN: 38.9 ± 0.04 °C; HS: 39.3 ± 0.04; P < 0.0001) and daytime (TN: 39.2 ± 0.09 °C; HS: 39.9 ± 0.08 °C; P < 0.0001) conditions. In STR, malondialdehyde-modified protein abundance (P = 0.1) and concentration (P < 0.1), markers of oxidative stress, tended to increase following Zen exposure, largely driven by the HS-Zen group. Heat stress increased protein expression of antioxidant enzymes catalase (p< 0.05) and superoxide dismutase 1 (P < 0.05), while Zen decreased glutathione peroxidase 1 (P < 0.05) transcript (P < 0.05) and protein (P < 0.05) abundance and enzymatic activity (P < 0.05). Although a mild HS paradigm and low Zen exposure were employed, oxidative stress markers were altered suggesting oxidative skeletal muscle is susceptible to HS- and Zen-mediated changes in redox balance. In total, these data raise the possibility that more severe HS exposures and greater Zen doses, similar to those sometimes encountered in production settings, may compromise muscle health.