Minimum Lethal Dose of Selenium, as Sodium Selenite, for Horses, Mules, Cattle, and Swine

Following the discovery of selenium in numerous plants grown in certain areas of the north-central Great Plains and its identification as the cause of so-called alkali disease of livestock in those areas, a number of experiments have been undertaken to test its toxicity. Most of this work was designed to study the effect of continued feeding of small doses of selenium in various forms to small experimental animals. The disease produced in this way was of the subacute or chronic type. In a few studies, however, large single doses of selenium have been administered, resulting in the acute type of poisoning. It appears that only small laboratory animals have previously been used for this work. Franke and Moxon,^ using rats, found that the minimum fatal dose (smallest dose that killed 75 percent or more of the animals in 48 hours) of selenium, in the form of sodium selenite, injected intraperitoneally was 1.5 mg. per pound of body weight. Of sodium selenate, the minimum fatal dose was found to be 2.5 mg. per pound of body weight. Smith, Stohlman, and Lillie,^ using rabbits, found that the fatal dose of selenium, in the form of sodium selenite or selenate, when administered orally was 1.5 to 2.0 mg. per pound of body weight. No reference has been found of any such experimentation with the larger domestic animals. In order to obtain information on this point, experiments were carried on in 1934 and 1938 at the Animal Disease Station, Beltsville, Md., to determine the minimum lethal dose of selenium for horses, mules, cattle, and swine. This work also afforded an opportunity to observe any symptoms and gross pathological changes which might result from acute selenium poisoning and how the element was distributed in the body tissues. The results of the experiments are reported in this paper.