Abstract :
This experiment evaluated the maximum tolerable level of inorganic Se fed to growing wether lambs for 1 year. Sodium
selenite was added to provide 0.2, 2, 4, 6, 8, and 10 ppm Se to a basal diet. Thirty-nine crossbred wether lambs initially
weighing 22.8 ± 3.3 kg were randomly allotted to one of six treatments. Blood samples were collected and liveweight gain
determined at 28-day intervals and tissue samples were collected at experiment termination. Serum, whole blood, wool,
hooves, bile and five tissues were analyzed for Se concentrations. Five tissues at experiment termination were microscopically
evaluated for tissue breakdown due to Se toxicosis. Also, five enzyme activities and albumin were determined. Lamb BW
were not influenced by dietary Se concentrations (P > 0.15). Both serum and whole blood Se concentrations increased at each
collection period as dietary Se level increased (P < 0.01) and the serum had a dietary Se level × time interaction (P < 0.01).
The whole blood Se concentration was two to three times greater than serum Se concentration. There was a strong positive
correlation (r = 0.92) between serum and whole blood Se concentration. At termination of the study, all tissues and wool,
hoof, and bile Se concentrations increased as dietary Se level increased (P < 0.01). Liver had the highest Se concentration
followed by the kidney in all but the lowest treatment of 0.2 ppm. Both gross and microscopic evaluation of tissues revealed
no significant lesions for any treatment groups. There was no apparent pathological suggestion of selenosis based on tissue
evaluation. Albumin and serum enzyme levels suggestive of tissue breakdown as a result of selenosis did not vary (P > 0.15)
among treatments, and enzymes were within their respective normal ranges. These results suggest that ≤10 ppm dietary Se
as selenite is not toxic to wether lambs when fed for 1 year. It seems plausible, therefore, to consider the maximum tolerable
level of Se as selenite for sheep to be considerably higher than 2 ppm as previously suggested.
© 2004 Elsevier B.V. All rights reserved.
