The influence of vitamin E on immune function and response to vaccination in older horses

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Horses have an increased susceptibility to infection because of a decline in immune function with advancing age. Vitamin E has been found to play a key role in normal immune system function. The purpose of the study was to examine the effect of vitamin E supplementation on immune function and response to vaccination in older horses. Predominantly older horses (18.9 ± 1.3 yr, range 7 to 26 yr; 523 ± 38 kg of BW) were supplemented orally once daily for 16 wk with either all-rac-α-tocopheryl acetate (15 IU/kg of BW; n = 8) or a placebo (n = 8). One horse from each group was removed from the study for reasons not related to the study. Serum α-tocopherol concentration, neutrophil and monocyte bacterial killing ability, lysozyme activity, immunoglobulin concentration (IgGa, IgGb, IgGT, and IgM), and neutralizing antibody production to West Nile virus vaccination were determined. The overall serum α-tocopherol concentration of the vitamin E-supplemented horses was greater than that of placebo-supplemented horses (P < 0.001). Bacterial killing capacity of monocytes and neutrophils increased in the vitamin E-supplemented horses (P < 0.05). Vitamin E-supplemented horses had greater serum IgGa (P < 0.001) and IgGT (P = 0.003) concentrations but produced less serum IgGb (P = 0.023) than placebo-supplemented horses. There was no effect of vitamin E supplementation on IgM production. The neutralizing antibody response to vaccination against West Nile virus was unaffected by vitamin E supplementation. There was a continuous increase in serum lysozyme concentration in placebo-supplemented horses, whereas serum lysozyme concentration did not increase until wk 12 in vitamin E-supplemented horses. In conclusion, vitamin E supplementation of predominantly older horses differentially modulated general cell-mediated and humoral immune function. Further research is needed to fully understand the effect of vitamin E on the immune function of horses. © 2010 American Society of Animal Science.

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Journal of Animal Science