Review: The Potential Role of Vitamin E Analogs as Adjunctive Antioxidant Supplements for Transition Cows

Abstract

Despite routine supplementation of dairy cattle with vitamins with antioxidant functions, such as α-tocopherol, the high energy demand of the transition period creates a pro-oxidant state that can overcome antioxidant defenses and damage macromolecules. Known as oxidative stress, this condition impairs host immune defenses, predisposing cattle to disease and causing dysfunctional inflammation through a dysregulated production of lipid inflammatory mediators known as oxylipids. Non-α-tocopherol analogs of vitamin E have functions in other species that limit oxidative stress and dysfunctional inflammation but have largely remained unstudied in cattle. As non-α-tocopherol analogs of vitamin E have functions similar to α-tocopherol yet are more rapidly metabolized, they may provide further antioxidative functions with a reduced risk for adverse effects. Indeed, in vitro and in vivo evidence in cattle show a strong safety profile of most non-α-tocopherol analogs, and by several measures, non-α-tocopherol analogs present equally or more potent antioxidative activities than α-tocopherol alone. Further, vitamin E analogs are shown to compete with certain fatty acids for enzymatic metabolism, which may impact proinflammatory mediator production. Given that non-α-tocopherol analogs of vitamin E reduce the production of pro-inflammatory mediators and act as potent antioxidants, their safety and efficacy for these purposes should be further evaluated in cattle.