Comparative Toxicity of Selenium from Seleno-DL-methionine, Sodium Selenate, andAstragalus bisulcatusin Pigs

Abstract

Selenium is an essential micronutrient, although ingestion in excess in pigs can cause disease conditions including neurological dysfunction and chronic skin and hoof lesions. Controlled feeding trials in growing swine, using the same Se content in feed sources, resulted in higher concentrations (p≤ 0.05) of Se in blood and organs of pigs fed seleno-DL-methionine compared with those receivingAstragalus bisulcatusor sodium selenate. Clinical signs of Se toxicity including neurological signs of paralysis were more severe and occurred sooner in theA. bisulcatusgroup than in the sodium selenate or seleno-DL-methionine groups. All five pigs fedA. bisulcatusdeveloped neurological signs of paralysis, and in four the signs occurred within 5 days of the start of treatment. Four of five pigs fed sodium selenate also developed paralysis, but this occurred 4 to 21 days after treatment began. The fifth pig in the group developed signs of chronic selenosis. Two of five pigs fed seleno-DL-methionine developed paralysis on 9 and 24 days, respectively, and the remaining three developed chronic selenosis. Selenium fed to pigs in three forms [plant (A. bisulcatus), sodium selenate, or seleno-DL-methionine] resulted in neurological dysfunction and lesions of symmetrical poliomyelomalacia. These were most severe in theA. bisulcatusgroup, which also had polioencephalomalacia. Although seleno-DL-methionine caused the greater increase in tissue and blood Se concentrations, this did not correlate with severity of pathological changes, since animals fedA. bisulcatusdeveloped more severe and disseminated lesions.