Reasons for performing study: Dietary intake and feeding management practices could affect the degree of physiological stress and subsequent performance of high level 3-day event horses.
Objectives: To assess whether a relationship exists between dietary intake levels of selected nutrients and the inflammatory and antioxidant status in horses competing in a high level 3-day event.
Materials and methods: Riders competing in a CCI2*/CCI3* 3-day event (n = 35) answered a nutritional management survey conducted by the investigators at the competition. Actual and recommended intakes of vitamin E, potassium (K), calcium (Ca), phosphorus (P) and magnesium (Mg) were calculated using the manufacturer or NRC values. Blood samples, bodyweight and body condition score of horses were taken precompetition, 30 min and 18–24 h after cross-country, but before stadium jumping. Data were analysed using a mixed model ANOVA with repeated measures and Pearson's product moment correlation.
Results: Estimated daily intakes of vitamin E, K, Ca, P and Mg for horses were higher than daily recommended levels (P<0.05). In response to competition, tumour necrosis factor-α (TNFα; P = 0.0002), nitric oxide (NO; P = 0.013) and β-carotene (BC; P<0.0001) decreased, creatine kinase (P<0.0001) and aspartate aminotransferase (P = 0.001) increased, and α-tocopherol and retinol did not change. Intake of vitamin E, K, Ca, P and bodyweight were negatively correlated with TNFα (P<0.05). Vitamin E and bodyweight were also negatively correlated with NO (P<0.05). Pasture intake and BC were positively correlated (P<0.0001).
Conclusions: The decline in systemic inflammatory markers is probably due to increased utilisation or excretion and decreased production related to the increased oxidative stress experienced by horses during competition. High bodyweights could also predispose horses to a higher level of inflammation during 3-day event competition.