Selenium content and distribution in cow's milk supplemented with two dietary selenium sources

Area of Science:

• Animal Nutrition
• Dairy Science
• Trace Element Metabolism

Background:

• Selenium (Se) is an essential trace element crucial for animal health and milk quality.
• Dietary selenium supplementation can enhance milk selenium content, but optimal sources and levels require investigation.

Purpose of the Study:

• To evaluate the efficacy of selenized yeast (Se-Y) versus sodium selenite as dietary selenium sources for dairy cows.
• To determine the impact of Se-Y supplementation levels on milk selenium concentration and its distribution in milk components.
• To assess the kinetics of selenium transfer into milk.

Main Methods:

• A 6-week study on three farms involving dairy cows fed total mixed rations (TMR) supplemented with either Se-Y or sodium selenite.
• Dose-response study on two farms to assess the effect of varying Se-Y levels (0-0.5 microg g(-1)) on milk Se.
• Analysis of milk selenium content and its distribution in whey, casein, and fat.

Main Results:

• Selenized yeast (Se-Y) supplementation at 0.3 microg g(-1) maximized milk selenium increase (9 microg L(-1)) within 5 days, with sustained levels.
• Increasing dietary Se-Y from 0 to 0.5 microg g(-1) elevated milk Se from 20 to 39 microg L(-1).
• Selenium distribution in milk components (whey, casein, fat) remained constant regardless of the selenium source or level.

Conclusions:

• Selenized yeast is a highly effective source for increasing milk selenium content in dairy cows.
• Dietary Se-Y supplementation allows for the production of cow's milk with tailored selenium enrichment.
• The form of selenium supplementation does not alter its distribution within milk fractions.