Impact of zinc and arginine dietary supplements on antioxidant capacity and oxidative status in weanling piglets under conditions of commercial production

Abstract Text: The effects of high levels of zinc (Zn) and arginine (Arg) supplementation on the antioxidant capacity and oxidative status of weanling piglets raised under commercial conditions were examined. Weanling piglets aged 21 d were fed for 15 days a diet supplemented or not with 2500 mg kg^-1 of Zn and 1% Arg. They were distributed among the four treatments in a randomized complete block design based on initial body weight, six pens per treatment, 13 animals per pen. Access to feed was ad libitum. Data were analyzed as a 2 x 2 factorial experiment using the SAS MIXED procedure, with Zn and Arg supplementation as the main independent variables. Blood sampling day was included as a third factor. Blood was collected from the same two piglets in each pen before the morning feeding on days 8 and 15. The Zn supplement increased average daily gain (ADG) from days 0 to 7(0.194 vs 0.140 g d^-1), days 7 to 15(0.368 vs 0.280 g d^-1) and for the entire experimental period(0.289 vs 0.217 g d^-1), average daily feed intake (ADFI) from days 0 to 7(0.197 vs 0.182 g d^-1), days 7 to 15 (0.454 vs 0.358 g d^-1) and for the entire experimental period(0.338 vs 0.279 g d^-1) and ADG:ADFI ratio from days 0 to 7(0.991 vs 0.760), and for the entire experimental period (0.860 vs 0.777)(P<0.001). Both supplements decreased the malondialdehyde concentration significantly (Zn:4.37 vs 3.91 , P<0.005;Arg:4.38 vs 3.89 µmol L^-1,P<0.002). Total antioxidant capacity increased from day 8 to 15 (0.953 vs 1.391 μmol equivalent Trolox L^-1), regardless of the dietary treatment (P<0.05). The reduced glutathione concentration also was higher on day 15 than on day 8 (3.37 vs 2.22 μmol L^-1), regardless of the dietary treatment (P<0.001). On day 8, the concentrations of total and oxidized glutathione were increased when Arg and Zn supplements were combined(Zn2500Arg1:5.42 and 1.20; Zn0Arg0: 4.19 and 1.04 µmol L^-1), but decreased in the presence of either supplement alone (Zn2500Arg0:2.57 and 0.41; Zn0Arg1:3.42 and 0.67 μmol L^-1)(P<0.001). Piglets fed Zn-supplemented diets had a lower haptoglobin serum concentration than those fed a non-supplemented diet(509.5 vs 1417.6 mg L^-1;P<0.001). In conclusion, although a high level of Zn improved piglet growth performance, the results do not indicate any clear association between performance and oxidative status. Arginine supplementation had a limited effect on growth performance and oxidative status under these commercial conditions.

Keywords: piglets, zinc, arginine