The impact of Zearalenone on heat-stressed skeletal muscle in pigs.

Heat stress (HS) and Zearalenone (ZEN), a toxic feed contaminant, affect growth, production efficiency, and animal welfare, and can cause death. As HS and ZEN independently increase oxidative stress, an imbalance of free radical production and clearance, and the likelihood of ZEN contamination during heat events, we hypothesized concomitant exposure would induce oxidative stress in pig skeletal muscle more than either agent alone. To address this, female pigs were treated with a placebo or low dose of ZEN and exposed to ambient temperature or a mild cyclic HS designed to mimic environmental conditions (hot days, cooler nights) for 7 d. Following these treatments, fast- and slow-twitch muscles were collected for analysis. In slow-twitch muscle, we observed increased markers of oxidative stress in pigs exposed to ZEN primarily driven by HS and ZEN treated pigs. Additionally, ZEN reduced antioxidant abundance and enzymatic activity regardless of the environment. Conversely, HS and/or ZEN did not cause oxidative stress in fast-twitch muscle, although ZEN altered antioxidant abundance. Although a mild HS and ZEN dose was used, oxidative stress markers were altered, suggesting that slow-twitch muscle is susceptible to HS- and ZEN-mediated changes. These data raise the possibility that more severe HS exposures and higher ZEN doses may compromise muscle health.