Vitamin E Supplementation May Improve Immune Response in Older Horses
Horses are living longer than ever these days. Roughly 15% of horses in the United States are over the age of 20. Because immune function tends to decrease with advanced age, these horses are more susceptible to disease and infection. Vitamin E is a potent antioxidant that plays an important role in ensuring normal function of immune cells. Research suggests that vitamin E supplementation may enhance immune function in aged humans, including antibody production after vaccination (1).
There is not a lot of research available regarding the effects of vitamin E supplementation on equine immune function. Therefore, a group of researchers from the University of Rhode Island and Virginia Tech University designed a study to examine immune function in horses that received a vitamin E supplement.
For the study, the group used horses (geldings and mares) of various breeds that ranged in age from 12 to 26 years. Horses in the vitamin E supplemented group were fed 15 times the daily recommended amount of vitamin E once per day. Horses in the control group were fed a placebo, which was an equivalent weight of wheat middlings. All horses were fed a mixed grass hay. Horses were injected at week 7 and 14 of the study with a recombinant West Nile Virus (WNV) vaccine to determine if vitamin E improved antibody production to WNV.
Blood was collected from the horses at the beginning of the trial and at two-week intervals throughout the study and used to determine blood levels of vitamin E. Levels of immunoglobulins, or antibodies, in blood were also measured. Immune cells were isolated from blood on weeks 6 and 16 of the study to determine if vitamin E enhanced their ability to kill bacteria.
Results showed that supplementation of vitamin E at 15 times the recommended level increased blood levels of vitamin E. It also enhanced several components of the immune system of older horses. Immune cells from horses fed vitamin E showed increased ability to kill bacteria, which is important at warding off potential bacterial infections. Certain types of immunoglobulins increased after supplementation with vitamin E. Interestingly, neutralizing antibodies specific to WNV were not affected by vitamin E supplementation. Certainly, additional research into modulatory effects of vitamin E on the immune system of horses is needed. Contact your equine nutritional consultant if you are considering adding supplemental vitamin E to your horse’s diet.
(1) Meydani, S.N., S.N. Han, and D. Wu. 2005. Vitamin E and immune response in the aged: molecular mechanisms and clinical implications. Immunol. Rev. 205:269-284.
(2) Petersson, K.H., D.B. Burr, M. Gomez-Chiarri, and C.S. Petersson-Wolfe. 2010. The influence of vitamin E on immune function and response to vaccination in older horses. J. Anim. Sci. 88:2950-2958.