Selenium metabolism and toxicity of inorganic and organic selenium sources and levels on growth, reproduction and other mineral nutrients in swine

This dissertation examined the effects of high dietary levels of organic and inorganic Se on growth performance, toxicity characteristic in grower-finisher pigs and the long term effects on sow performance, and the tissue Se concentration and subsequent toxic symptoms in both the sow and progeny. The experiments demonstrated that feeding a diet containing 5 to 10 ppm inorganic Se (sodium selenite) or 15 ppm organic Se (Se-enriched yeast) resulted in toxic responses in grower-finisher pigs. Serum and tissue Se content increased as dietary Se level increased but was higher when organic Se was fed. Colored hair pigs (red or black) were more resistant to Se toxicity compared to white haired pigs in both Se sources. The excretion of the essential micro-minerals (Zn and Mn) increased in the bile as dietary Se level increased and was higher when pigs were fed inorganic Se. When inorganic Se was fed, Se toxicity occurred at 7 ppm, but at 10 ppm organic Se when fed to reproducing sows. Serum GSH-Px activity of sows and pigs was not affected by dietary Se level or source. Serum GOT activities at the 12 wk period increased as dietary Se level increased and were approximately 2 fold higher when pigs were fed inorganic Se. This suggested increased cellular damage as dietary Se level increased particularly when inorganic Se was fed. Dark colored of bile at high dietary Se levels suggested that hepatic tissue damage occurred. Selenium transfer through the placenta and milk from dam to litter was higher when organic Se was provided during gestation and lactation. Tissue and serum Se concentrations of sows and pigs were higher when sows were fed organic Se. This demonstrated that the labile Se (liver) when the organic Se was provided supported high milk Se concentration. The higher Se transfer from dam to litter consequently increased the Se status of progeny when organic Se was fed. Hoof separation and hair loss in nursing pigs at 14 days of age occurred above 7 ppm Se when sows were fed inorganic Se. When organic Se was provided, only hair loss was observed at 10 ppm Se. Hair Se concentration was a good indicator of Se status, particularly when pigs were fed high levels of Se. Amino acid composition of pig hair was similar among three different colored hair (white, red and black) pigs. Red colored hair of gilts contained more Se and thicker than white colored hair when gilts were fed normal diets containing .3 ppm of inorganic Se. Consequently, Se requirement may differ by breed hair color. Hair Se content and hair diameter were affected by hair location of the body.