Growth performance and meat quality of finishing pigs fed diets supplemented with antioxidants and organic acids in late summer

Context. Heat stress compromises growth performance and meat quality and results in economic losses in pork production. Aims. We investigated the effects of supranutritional levels of selenium (Se) and vitamin E (VitE), along with organic acid blends, on the growth performance and meat quality of finishing pigs over a period of weeks during late summer to early autumn in Westbrook, Queensland, Australia. Methods. A total of 264 crossbred pigs (25.8 +/- 2.4 kg, mean +/- s.d.) at 11 weeks of age were randomly assigned in a 2 x 2 x 2 factorial design with two aging times (2 or 5 days) nested within each pig. The factors included antioxidants (Se/E, with recommended or supranutritional doses of Se and VitE), an organic acids (OA) blend added to drinking water (control vs supplemented), and sex (female vs male). Key results. Between 16 and 18 weeks of age, high Se/E decreased daily feed intake (P = 0.010) but had no effects on average daily gain or feed conversion efficiency (FCE). Male pigs grew faster (P = 0.040) and had a higher FCE than females (P = 0.050). Supplementation with OA increased FCE in males but not females (OA x Sex interaction, P = 0.035). Between Weeks 16 and 20, male pigs grew faster (P < 0.001), tended to eat more (P = 0.057), and had higher FCE (P = 0.002) than females (P < 0.001). There were no main effects of Se/E or OA on meat quality, except protein oxidation was reduced by high Se/E (P = 0.047). Sex impacted only Warner-Bratzler shear force (WBSF), with male pigs having lower WBSF than females (P = 0.053). Meat aging decreased WBSF (P < 0.001), but it increased cooking loss (P = 0.036), myofibrillar fragmentation index (P < 0.001), lipid oxidation (P < 0.001) and colour parameters (P < 0.001 for all). Conclusions. Supplementation with Se/E for up to 10 weeks and OA for 5 weeks did not influence production parameters or pork quality in late summer, except that high Se/E decreased protein oxidation, and significant heat stress conditions were not experienced as expected. Implications. Supplementation with Se/E and OA may be effective when environmental temperatures are higher.