Influence of various selenium sources on selenium concentration in the milk of dairy cows

Selenium (Se) as essential trace element is supplemented in various compounds to rations of food producing animals. In human nutrition the range between Se requirement and upper level is very small (1:3-5). Hence, food of animal origin may contribute to Se supply of humans, but can also offer high amounts of Se and exceed the Se upper level for humans. Therefore the transfer into the milk of inorganic (0.2 and 0.4 mg Se from sodium-selenite) or organic (Se methionine) Se-compounds was tested. Fifteen lactating German Holstein cows were fed diets without supplementation (0.1 mg Se/kg dry matter, DM) or supplemented with inorganic or an organic Se-compound over 3 weeks. Se-supplementation did not significantly influence feed intake, milk yield and composition as well as animal health. Se-concentration of milk increased from 13.3 over 17.6 to 19.7 mu g/L in the case of inorganic Se supplementation and from 13.9 over 24.6 to 54.8 mu g/L after Se-yeast addition.