Effects of dietary aid on lipid peroxidation and antioxidant capacity after exercise in young horses

Abstract

During training, young horses experience intense exercise that can disrupt the gastrointestinal environment, contributing to increased oxidative damage and decreased antioxidant capacity. Supplementing dietary aids may support systemic oxidative balance following intense exercise. Therefore, the objective of this study was to determine the effect of a dietary aid on lipid peroxidation and total antioxidant capacity (TAC) following a submaximal exercise test (SET). It was hypothesized the dietary aid would decrease lipid peroxidation and increase TAC. To test this hypothesis, twenty 2-year-old stock-type horses from an established herd with no history of forced exercise were individually housed and allowed a 14-d acclimation period. Horses, balanced by body weight (BW; 417 ± 35 kg) and sex, were offered 0.75% BW concentrate/d containing no dietary aids (CON; n = 10) or a blend of pre-, pro-, and post-biotics, marine calcite, and organic trace minerals (Digestive Shield; DS; n = 10). On d 0, horses began supplementation and a progressive exercise program, increasing intensity every 7 d. On d 30, horses completed a 1 h SET. Blood samples were collected via jugular venipuncture on d 0, before supplementation, and before (PRE), immediately after (POST), 0.5, and 1 h after SET to evaluate circulating malondialdehyde (MDA), a marker of lipid peroxidation, and TAC in Trolox Equivalent (TE). Data were analyzed using PROC MIXED in SAS with fixed effects of dietary aid, time, sex, and their interactions. The effect of sex was nonsignificant (P ≥ 0.33) and removed to conserve degrees of freedom. Significance was declared when P ≤ 0.05 and a trend when 0.05 < P ≤ 0.10. On d 0, no differences were observed between CON and DS in MDA or TAC (P ≥ 0.17). Overall, circulating MDA was greater in CON (3.14 ± 0.15 µM) than in DS horses (2.68 ± 0.14 µM; P = 0.03). At PRE (3.47 ± 0.23 µM), MDA tended to be greater than 0.5 h (2.83 ± 0.23 µM; P = 0.06) and greater than 1 h (2.75 ± 0.23 µM; P = 0.03). At POST (3.01 ± 0.23 µM), circulating MDA did not differ from PRE, 0.5 h, or 1 h (P ≥ 0.30). Supplementing DS did not affect circulating TAC during the SET (CON: 0.90 ± 0.08 TE; DS: 0.87 ± 0.08 TE; P = 0.61). The time point relative to SET did not impact circulating TAC (PRE: 0.90 ± 0.10 TE; POST: 0.88 ± 0.10 TE; 0.5 h: 0.95 ± 0.09 TE; 1 h: 0.81 ± 0.09 TE; P = 0.66). These data indicate that supplementing DS may decrease lipid peroxidation but does not impact TAC after submaximal exercise in young horses. Further research should evaluate the impact of DS on DNA and protein oxidation in young exercising horses.