SELENIUM DEFICIENCY AND TOXICITY

Selenium Deficiency

Selenium is a trace mineral present in the soil in varying amounts around the world. In the United States, soil is selenium-deficient in parts of the Pacific Northwest, from the Great Lakes region to the New England states, and along the Eastern Seaboard into Florida. Local agricultural extension services usually maintain soil maps that indicate selenium levels. Because selenium levels can vary greatly within an area, testing the soil's selenium content is recommended. Soil is considered "selenium deficient" when there is less than 0.5mg of selenium per kg of soil.

Soil selenium levels affect this mineral's absorption by growing plants that are ultimately eaten by goats. Proper selenium levels are necessary for goats to reproduce, lactate, give birth, urinate, and have properly functioning muscles. Symptoms of selenium deficiency are similar to those of Vitamin E deficiency. White Muscle Disease, also known as Nutritional Muscular Dystrophy, is a condition in which kids are too weak to stand or suckle at birth, they consistently cough, milk sometimes runs out of their nose after nursing, and they develop pneumonia because of muscle weakness in their lungs. In adults, abortions, stillbirths, retained placenta, or inability to conceive may result from selenium deficiency.

Selenium is routinely added to processed grain by feed mills, but the amount permitted by US law may be insufficient for some areas. Therefore, many producers obtain a veterinary prescription for either injectable or oral supplements. Dosages vary by region and should be discussed with a knowledgeable vet, but the following is a general outline of how many producers supplement their goats with adequate selenium levels:

Shortly before breeding season, give all adults, including breeding bucks, injectable selenium (BoSe). Bucks should receive BoSe injections at least twice a year. Pregnant does are again supplemented with BoSe four to six weeks before kidding. Kids are injected with BoSe at birth, again at one month of age, and if the soil is very selenium deficient, injections are repeated at two and at three months of age. Use the "minimum dosage" at birth. Although BoSe is not approved for use in goats, producers generally use twice the labeled sheep dosage. Discuss your goats' needs in detail with your local vet and agricultural extension service representative.

Selenium Toxicity

Selenium has a very narrow margin of safety. Goats require 0.2 parts per million of selenium, and the toxic level is 3 ppm. Some symptoms of selenium deficiency are identical to those of selenium toxicity. A doe's failure to conceive can be the result of either selenium deficiency or toxicity. Kidney failure, stillbirth, and abortions also may be attributable to either end of this spectrum. By contrast, hair loss in the beard and flank regions and cracks and deformities in horns and hooves may reveal an overabundance of selenium in the goat's diet. Over-concentrations of selenium occur in parts of North Dakota, South Dakota, Nevada, Idaho, California, Arizona, New Mexico, and adjacent states. See your local agricultural extension agent for information on concentrations in your area. Certain "indicator" plants reveal a toxic level of selenium in the soil. Some species of Astragalus (locoweed) indicate the presence of high levels of soil-based selenium. Goats actually become addicted to these plants if they are not completely removed from this forage.

Symptoms of severe selenium toxicity include impaired vision and staggering ("blind staggers"), rear legs which won't support the body, then muscle weakness in the front legs, and progressive weight loss. Each of these symptoms can also be symptoms of other illnesses, so the producer should determine his area's selenium conditions in advance to avoid an incorrect diagnosis..

Once a goat has severe selenium toxicity, there is no known effective treatment. Removing the affected animal from the area where the problem occurred and performing supportive therapy is the best chance of saving the goat. Goats affected by selenium toxicity remain bright, alert, and are eating well up to the time of death.

The author, Suzanne Gasparotto, hereby grants to local goat publications and club newsletters, permission to reprint articles published on the Onion Creek Ranch website under these conditions: THE ARTICLE MUST BE REPRODUCED IN ITS ENTIRETY AND THE AUTHOR'S NAME, ADDRESS, AND CONTACT INFORMATION MUST BE INCLUDED AT THE BEGINNING OF THE REPRINT. We would appreciate notification from any clubs or publications when the articles are used. (A copy of the newsletter or publication would also be a welcome addition to our growing library of goat related information!)

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