Antioxidant and osmolyte enriched or energy-dense diet: effect on heat-stressed finishing pigs

Heat stress negatively affects pig welfare, health, and production. Osmolytes and antioxidants are considered potential mitigators of heat stress-induced damage. Modification of feed composition, specifically lower crude protein, also aims to reduce internal metabolic heat production.

Objective: The aim of this study was to investigate the effect of an enriched or energy-dense (E-dense) diet on 192 heat-stressed fattening pigs.

Methods: Dietary treatments were administered when pigs reached ± 80 kg. The control diet comprised 15% CP, 3.6% crude fat, 9.1 MJ/kg net energy, 0.4 mg/kg inorganic selenium (Se), and 100 ppm vitamin E; the enriched diet contained the same chemical composition but was supplemented with 0.2 mg/kg inorganic Se, 0.2 mg/kg selenomethionine, 200 ppm vitamin E, 200 ppm vitamin C and 0.1% betaine; the E-dense diet featured 13.6% CP, 6.6% crude fat, and increased energy (9.7 MJ/kg) and lysine content. The lysine:energy ratio of all three diets was the same. A 1-week heat wave (± 30 °C and Temperature - Humidity Index of ± 78.4) was induced 2 times when pigs were 20 and 22 weeks old. Physiological parameters and performance parameters were assessed weekly. At the end of the trial, carcass and meat quality were evaluated.

Results: Additive enrichment of the diet resulted in a numerically increased daily gain over the 6-week trial compared to the control group. The E-dense group had a higher increase in rectal temperature during heat load compared to the control group. Over the entire trial, the E-dense group had a higher feed conversion ratio than the control group. Carcass traits revealed increased fat thickness of 0.9 mm in the E-dense group, along with lower lean meat content. The meat of the enriched group displayed elevated vitamin E and Se levels, which may be beneficial for the consumer.

Conclusion: The nutritional strategies did not prevent physiological heat stress or enhance performance, but the supplementation of antioxidants and osmolytes tended to ameliorate daily gain over the entire trial.