THE EFFECT OF FEEDING ORGANICALLY BOUND SELENIUM AND ALPHA-TOCOPHEROL TO DAIRY-COWS ON SUSCEPTIBILITY OF MILK TO OXIDATION

Twenty-four lactating Holstein cows were used to compare the effect of two sources of supplemental selenium with or without supplemental dl-alpha-tocopherol acetate, on oxidative stability of their milk. The Se sources were inorganic Se mixed in the concentrate ration or alfalfa sprayed with 20 g Se ha-1 four wk before ensiling. Half of the cows on each treatment received 3000 IU d-1 of dl-alpha-tocopherol acetate for the first 4 wk (Period 1) and the other half received the tocopherol for the second 4 wk (Period 2). Improvement (P < 0.01) in flavour scores due to alpha-tocopherol supplementation were apparent only when 0.1 mg Cu kg-1 was added to the milk to catalyze oxidation. Plasma tocopherol content was increased (P < 0.01) when tocopherol was fed regardless of Se treatment. Milk tocopherol content increased (P < 0.01) when the cows were fed both supplemental Se and tocopherol; however, the increase was not significant (P > 0.05) when the tocopherol was fed without Se. Plasma and milk Se contents were higher (P < 0.01) for cows fed the Se-fertilized alfalfa than for the control cows or those fed the inorganic Se. In whole blood there were no significant differences in Se content in Period 1 but levels were higher (P < 0.01) for the cows fed Se-fertilized alfalfa in Period 2. Although feeding Se-fertilized alfalfa (802 +/- 128-mu-g Se kg-1 DM) resulted in higher milk Se than feeding either the unsupplemented diet or the inorganic Se (398 +/- 44-mu-g Se kg-1 DM in the concentrate) this had no effect on the oxidative stability of the milk. The results suggest adequate Se improves the transfer of dietary tocopherol to milk.