PSIV-8 Effect of selenium and superoxide dismutase supplementation on heat stressed pigs

Heat stress (HS) compromises efficient production of pigs, in part by increasing oxidative stress and inflammation. Therefore the aim of this experiment was to investigate if supplementation of the anti-oxidants selenium or superoxide dismutase (SOD) could ameliorate HS in the pig. Sixty-four female Large White x Landrace pigs (av. 27.75) were acclimated one of the following diets: control (standard grower diet), selenium (Se, + 0.3 ppm organic Se), recombinant SOD (rSOD, 50 IU/d) and Se plus rSOD (SS) for 14 days under thermoneutral conditions (TN, 200C). All rSOD was administered top dressed in liquid form. Pigs were then moved to climate rooms and housed under TN or heat-stress (8 h 350C, 16h 280C/d) for 3 days and blood, urine and tissue collected for analysis terminally on d3. All data was analysed using an ANOVA with Tukeys post-hoc tests. Heat stress increased respiration rate (RR), reduced blood pCO2 and HCO3-, which coupled with a lower base excess indicated that the pigs were experiencing respiratory alkalosis. Furthermore HS increased rectal and skin temperatures, and reduced thyroid hormone (T4) concentrations, however HSP 27 and 70 concentrations were not influenced. Heat stress increased plasma adiponectin and IL-1b, reduced SOD and TNF-a, while no changes in IL-6 and leptin were observed. The effects of the anti-oxidant diets were that Se and SS increased RR, however parameters of respiratory alkalosis were not negatively influenced. The Se diet reduced T4 independently of HS. No improvement in plasma SOD was observed with the rSOD diets, but rSOD reduced adiponectin in HS pigs and both rSOD and SS reduced IL-6 overall. In conclusion a reduction in inflammatory responses were observed with the antioxidants Se and rSOD, including during HS and therefore may be a useful addition to existing amelioration strategies to ameliorate seasonal heat stress in pigs.