Estimation of the Relative Biological Availability of Inorganic Selenium Sources for Ruminants using Tissue Uptake of Selenium

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Abstract
An experiment was conducted to estimate the relative bioavailability of inorganic Se sources based on tissue Se deposition following supplementation at high dietary levels. Twenty-eight crossbred wethers averaging 50 kg initial weight were assigned randomly to seven treatments that were fed for 10 d. The basal diet contained .18 mg/kg Se (DM basis). Dietary Se was added at 0, 3, 6 or 9 mg/kg as reagent grade sodium selenite (Na2 SeO3) and 6 mg/kg from either calcium selenite (CaSeO3), Na2 SeO3 + fumed amorphous carrier or sodium selenate (Na2 SeO4). There were four sheep per treatment group, housed in individual, raised pens with slatted floors. Daily feed intake was restricted to 1,200 g and tap water was available ad libitum. The basal diet was fed for a 10-d adjustment period, then sheep were fed experimental diets for 10 d. At the termination of the experiment, blood samples were taken; sheep were stunned and killed, and livers and kidneys were removed and frozen for Se analysis. There was a linear (P < .001) uptake of Se in liver, kidney and serum. The CaSeO3 and Na2SeO4 sources resulted in greater (P < .05) Se concentrations in liver and kidney than did Na2 SeO3, but these differences were not significant when the analyzed dietary Se concentrations were used as a covariate in the statistical model. Based on linear and multiple linear regression slopes and average increases in serum, liver and kidney Se concentrations, estimated relative bioavailability values, corrected for analyzed dietary concentration, were 100, 101, 90 and 133 for Na2 SeO3 , CaSe03, Na2 SeO3 + carrier and Na2 SeO4, respectively. Copyright © 1988. American Society of Animal Science . Copyright 1988 by American Society of Animal Science.