What Type of Vitamin E Is Most Efficiently Absorbed by Horses?

Nine mature unexercised Thoroughbred geldings were divided into three groups and supplemented with synthetic (SYN), natural-source (NAT), or micellized water-soluble vitamin E (WS). Horses were maintained on a diet of unfortified sweet feed and grass hay and were muzzled during turnout to prevent grazing.

Baseline blood samples were taken following 14 days of no supplementation. Horses were then supplemented with 500 IU of vitamin E from the assigned treatment source for 14 days. The dose rate of vitamin E was doubled at 14-day increments up to 8,000 IU. Plasma tocopherol levels were measured at the end of each 14-day period.

Plasma tocopherol levels were significantly elevated from the baseline in the WS and NSAT groups at 1,000-8,000 IU, respectively. No significant difference was recorded in the SYN group as dose rate was increased. Significant differences among groups were recorded at various dosage rates, with WS always at highest and SYN always at lowest levels.

This KER research was conducted in 2004.