Effects of Commercial Antioxidants in Feed on Growth Performance and Oxidative Stress Status of Weaned Piglets

SIMPLE SUMMARY: Supplementation with high levels of vitamin E (Vit E) is usually recommended for diets used during the post-weaning (PW) period, when piglets show reduced growth rate and are more susceptible to disease. We tested two commercial antioxidants (AOX) in pre-starter and starter diets to evaluate the growth performance and oxidative status of weaned piglets. At the end of each feeding phase, growth data and serum samples were collected. Data analysed were body weight (BW), average daily gain (ADG), average daily feed intake, and feed conversion ratio (FCR). As oxidative stress indicators, total antioxidant capacity, total serum thiols, superoxide dismutase, glutathione peroxidase, thiobarbituric acid reactive substances (TBARS), and Vit E (α-tocopherol) were determined in serum. At the end of the study, cortisol and interleukin-6 were also determined, as well as TBARS and α-tocopherol concentrations in liver and muscle. The lowest BW, ADG, and FCR were found in piglets fed a low Vit E diet without AOX for the starter period. The α-tocopherol levels in serum and liver and differences among treatments were in agreement with the experimental design. Using AOXs or usual Vit E levels in feed was shown to be a key factor in maintaining optimal performance in the PW period. ABSTRACT: This work aimed to evaluate the effect of adding two different commercial antioxidants (AOX) products to pre-starter and starter diets using low vitamin E (Vit E as DL-α-tocopheryl acetate) levels on the growth performance and oxidative stress of piglets for the first six weeks post-weaning (PW). They were sorted by initial body weight (BW: 6.175 ± 0.931 kg) and randomly allotted to four dietary treatments (with six replicates per treatment): a positive control (PC) and a negative control (NC) diet, with normal and low dose of vitamin E (80 and 15 mg kg(−1), respectively), both without AOX; the other two experimental diets with a low dose of vitamin E (LVE) plus LOXIDAN VD100 (LVE + AOX1) or LOXIDAN E Ros (LVE + AOX2). Growth data were recorded, and blood samples were taken, at the beginning (day 0) and at the end of each feeding period: pre-starter and starter (at days 14 and 42, respectively). No differences among dietary treatments were found with respect to growth performance in the pre-starter period (p ≥ 0.05). However, at the end of the starter period, a lower BW was found in piglets fed the NC diet compared to the other dietary treatments. Differences in daily gain and feed conversion ratio were also found either for the starter period or when the whole period was considered (p < 0.05), whereby piglets fed PC or LVE diets supplemented with AOX showed better growth performance compared to piglets fed the NC diet. Regarding Vit E (α-tocopherol) serum levels, there were no differences among treatments at day 0; but the serum values of this vitamin decreased in LVE diets at 14 and 42 days, but not in the PC. On day 42, the highest levels of α-tocopherol in liver were also found in piglets fed PC (p < 0.05). Nevertheless, in general, from a metabolic point of view and after checking the serum biochemical profile of piglets, there were no differences in other oxidative stress markers (p ≥ 0.05). The results showed that the AOX products used were able to compensate for the lower Vit E supply with respect to growth performance in the starter phase. The use of AOXs or usual levels of Vit E in feed constitutes a key factor in achieving optimal growth performance of piglets in the PW period.