PSVII-13 - The evaluation of natural vs synthetic vitamin E supplementation for the management of alpha-tocopherol serum levels in Morgan horses.

Abstract: Vitamin E is an important lipid-soluble antioxidant that is tied to normal neuromuscular function in adult horses. Deficiency in serum vitamin E concentrations have been associated with several equine diseases such as Equine Motor Neuron Disease and Equine degenerative myeloencepalopathy. Horses with restricted access to pasture and genetic predispositions, like the Morgan Horse, can be especially susceptible to being marginally low or deficient. Two types of supplemental forms of Vitamin E are available: natural form - d-alpha-tocopherol acetate and a synthetic form - dl-alpha-tocopherol with the natural form being more expensive for horse owners. The objective of this study was to compare the serum vitamin E levels of horses on a low dose of natural (d-alpha) versus synthetic (dl-alpha) vitamin E. Eight horses with marginal/deficient serum alpha-tocopherol (0.94 – 2.3 µg/mL) were enrolled in a randomized block design study. Blocks were balanced for age, body weight and pre-study vitamin E level and were assigned to one of two treatments. 1) NATURAL – 2,000 IU powder (d-alpha-tocopherol acetate) for 16 wk. 2) SYNTHETIC – 2,000 IU dl-alpha tocopherol acetate for 16 wk. Horses were housed in box stalls with daily turnout without access to grass. Horses were fed hay at 2% of BW and 0.45 kg of concentrate daily with vitamin E feed activity of 45.5 and 1378 IU/kg, respectively. Natural and Synthetic treatments were fed once daily with the AM feeding. To ensure horses consumed the powder d-alpha-tocopherol acetate and capsules of dl-alpha-tocopherol acetate, cookies made from alfalfa powder, gelatin and d-alpha-tocopherol acetate powder were created. Serum alpha-tocopherol was assessed pre-feeding every four weeks from 0-16 weeks. Overall, horses supplemented with Synthetic treatment had higher serum alpha-tocopherol than those supplemented with the Natural treatment (2.61 vs 2.34, respectively; SE = 0.08, P = 0.05). Both treatments increased serum alpha-tocopherol levels to normal ranges (2.0-4.0 µg/mL) for all horses by 4 weeks and maintained the normal levels with the exception of week 12 for horses receiving the Natural supplement compared to the Synthetic (1.81 vs 2.62 µg/mL). Because of this diversion, there tended to be a week x treatment interaction (P = 0.06). This study results indicate the use of a synthetic, more affordable Vitamin E supplement will elevate serum alpha-tocopherol levels similarly to natural supplements. However, further research is needed to determine how these supplements are utilized within the body.