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Heat stress significantly impacts animal production globally and is exacerbated by climate change. Finishing swine are particularly affected, showing decreased feed intake, slower growth, lower market weights, and increased fat deposition. Zinc (Zn) supplementation can mitigate these effects, with the effectiveness varying by Zn source. This study aimed to evaluate the effects of different Zn sources and levels on finishing pigs under long-term, cyclic heat stress.
Methods: Six hundred cross-bred pigs were housed under thermoneutral or cyclic heat stress conditions for 70 days. Heat stress pigs experienced higher temperatures simulating summer heat with intermittent acute heat waves. The study used a 2 × 6 factorial design, with two environments (heat stress vs. thermoneutral) and six dietary Zn supplements: (1) 50 mg/kg ZnO, (2) 130 mg/kg ZnO, (3) 50 mg/kg organic Zn, (4) 50 mg/kg ZnO + 40 mg/kg organic Zn, (5) 50 mg/kg ZnO + 60 mg/kg organic Zn, and (6) 50 mg/kg ZnO + 80 mg/kg organic Zn. Pigs were monitored for body weight and feed intake, and ultrasonically scanned to measure loin muscle area, backfat, and percent lean.
Results: Results showed that heat stress pigs had lower average daily gain and feed intake. A diet-by-environment interaction revealed that some Zn blends mitigated the negative effects of heat stress on growth performance. Specifically, a blend of Zn sources at 50-60 mg/kg improved average daily gain under heat stress.
Conclusion: The study suggests that the NRC requirement of 50 mg/kg Zn may be insufficient for optimizing growth performance in finishing pigs under both thermoneutral and heat stress conditions.
Mills KM, Mahoney JA, Duttlinger AW, Elefson SK, Radcliffe JS, Rambo ZJ, Richert BT. Effect of chronic cyclic heat stress and supplemented inorganic and organic zinc source levels on grow-finish pig growth performance and estimated body composition. Translational Animal Science. 2024; 8: txae029. https://doi.org/10.1093/tas/txae029