Selenium and Horses

Selenium, Normal, Deficiency, and Toxicity in Horses

by Robert N. Oglesby DVM

Introduction

Introduction » Selenium Functions » Selenium Requirements » Selenium Sources and Supplementation » Selenium and Vit E Related Diseases » Selenium and the Foal » More Info & Discussions

Toxic in excess, selenium is an essential nutrient. Known primarily as having a role, along with vitamin E, as an antioxidant, it is now widely acclaimed to have positive effects on immune response and to be an anticarcinogen with possible protective roles in many diseases. Though the hype may be greater than the actual effects, there is no doubt this is an important nutrient that horses may not be getting enough of. This article addresses the many issues of selenium as a nutrient and provides links to information on disease caused by a deficiency and excess of selenium.

Selenium Functions

Introduction » Selenium Functions » Selenium Requirements » Selenium Sources and Supplementation » Selenium and Vit E Related Diseases » Selenium and the Foal » More Info & Discussions

Normal metabolism produces reactive waste products that are damaging to cells. This damage occurs through oxidation. Unsaturated fatty acids, a major component of all cell membranes, are very sensitive to this type damage and their oxidation is quite harmful to cell function. The body has defense mechanisms to protect itself from oxidation-induced damage. These mechanisms use selenium and vitamin E working together to prevent damage. Though selenium is a necessary nutrient, it can be toxic in excess amounts.

Selenium Deficiency

With deficiency Overt disease is rarely caused by Se deficiency in adult horses. However subclinical effects probably occur in many tissues and reproduction, immune function, and the ability to train and exercise is enhanced with adequate Se / vitamin E status.

White muscle disease of foals is the best characterized disease caused by direct selenium deficiency. All of the diseases associated with low vitamin E status are exacerbated by low dietary selenium, ...more. If there is inadequate vitamin E, more peroxides are formed and, therefore, more selenium is needed; conversely, if there is inadequate selenium, fewer peroxides can be removed and, therefore, more vitamin E is needed to prevent their formation. Optimum amounts of both are necessary to minimize oxidation-induced tissue damage.

Selenium Toxicity

Selenium supplementation must be done carefully as in excess it can be toxic in amounts not much higher than recommended. Selenium toxicity can also occur without supplementation, on soils that are rich in selenium and some plants take up and concentrate the selenium in the soil. Very high doses can result in acute muscle damage and death.

More common is chronic toxicity with smaller but excessive doses. The selenium accumulates overtime. The primary clinical sign of chronic selenium toxicosis is one of generalized poor doing, more.

Selenium Requirements

Introduction » Selenium Functions » Selenium Requirements » Selenium Sources and Supplementation » Selenium and Vit E Related Diseases » Selenium and the Foal » More Info & Discussions

                       
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