Alterations of serum vitamin E and vitamin A concentrations of ponies and horses during experimentally induced obesity

Abstract

Vitamin A, vitamin E and retinol‐binding protein 4 (RBP4) are a focus of current obesity research in humans. The impact of body weight (BW) gain on fat‐soluble vitamins and its associated parameters in equines has not been previously reported. Ten Shetland ponies and 9 Warmblood horses, all adult geldings, non‐obese and healthy, were fed an excessive energy diet for 20 months to induce BW gain. Serum α‐tocopherol (vitamin E), retinol (vitamin A), retinol‐binding protein 4 (RBP4) and retinol/RBP4 ratio were analysed before BW gain induction and at six timepoints during the BW gaining period. The mean (±SD) % BW gain achieved during two years of excess energy intake was 29.9 ± 19.4% for ponies and 17 ± 6.74% for horses. Serum α‐tocopherol increased significantly in ponies and horses during excess energy intake and circulating α‐tocopherol levels correlated positively with α‐tocopherol intake (r = .6; p < .001). Serum retinol concentrations showed variations during the study but without relation to intake. Serum RBP4 decreased at the end of the study. The retinol/RBP4 ratio increased with BW gain without differences between ponies and horses. In comparison with human research, the increase in the retinol/RBP4 ratio was unexpected and needs further elucidation.