The effect of supplementing rations with seleniumand vitamin E on biochemical parameters in bloodand performance of cows in the early stage oflactation

Thirty-two cows (Black-and-White x HF) in the first 100 days of lactation were divided into 4 groups and fed rations composed of equal proportions of roughages and concentrates in amount of 1 kg per 2 kg of milk at yield exceeding 12 kg/day. The concentrates were supplemented with vitamin E (group I, 336 mg; groups II, III, and IV, 672 mg/cow/day) and selenium: group I, no supplementation; group II, 4 mg/cow/day as sodium selenite; group III, 4 mg/cow/day as selenium yeast; group IV, 2 mg/cow/day as selenium yeast.