Organic selenium supplementation increases muscle selenium content in growing lambs compared to inorganic source

The objective was to evaluate the selenium (Se) balance and Se concentration in serum, muscle and viscera as well hepatic glutathione peroxidase activity (GSH-Px) in lambs fed diets supplemented with different Se sources and levels. Forty male Suffolk lambs 90 +/- 2.5 days old (19.8 +/- 2.1 kg) received, during a 84 days period, a total mixed ration (TMR) with three Se sources [Sodium selenite (Na selenite), Selenium-Yeast (Se-Yeast) and Selenium-Methionine (Se-Methionine)] and three Se levels [0.2, 0.8 and 1.4 mg/kg dry matter (DM)]. Also, it was provided a control diet (no addition of Se) for regression comparisons. Contrasts and estimates were used for partition specific treatment effects and serum data were analyzed by time repeated measures. Absorption and retention of Se as well as Se excretion by feces and urine were higher as Se inclusion increased. At 1.4 mg/kg DM level, there was higher Se excretion by feces with inorganic source compared to organic sources. Also, linear increasing was detected to absorption of Se among sources supplemented relative to its intake. Regarding the Se retention efficiency (g/100 g of Se consumed) the Se-methionine treatment showed a linear pattern. Selenium concentrations in serum and liver were higher, regardless of the source, linearly to dose inclusion. The amount of Se in muscle was higher for organic sources at level 0.8 and 1.4 mg/kg DM. At the first cited level, Se-Methionine was superior compared to Se-Yeast and at the second, the opposite occurred. In addition, organic sources leaded to linear effect of Se content in muscle tissue. However, there was higher hepatic GSH-Px activity to Na selenite source compared to organic sources. Regarding to relative Se content, organic Se sources had higher content in muscle tissue compared to Na selenite.