Effects of marginal selenium deficiency and winter protein supplementation on growth, reproduction and selenium status of beef cattle.

Seventy-two Hereford X Simmental cows, averaging 498 kg in body weight and 5.2 yr of age, were used in a 2-yr study to ascertain if selenium (Se)-vitamin E (E) injections and winter protein supplementation would affect growth, reproduction and health of beef cattle maintained year-round on feedstuffs marginally deficient in Se (.03 to .05 mg/kg). Cows received either no injection or a mixture of 30 mg Se (as sodium selenite) and 408 IU E injected subcutaneously beginning 3 to 4 mo prepartum and at 60-d intervals throughout the 2-yr period. Calves born to Se-E treated cows were injected with 5.5 mg Se and 75 IU E/100 kg body weight at 60-d intervals beginning at 1 mo of age. Calves were born between December 30 and February 20 and cows were bred between March 20 and May 20. Cattle grazed pasture (.05 mg Se/kg) that consisted of orchardgrass, bluegrass and white clover during the fall, spring and summer. During winter (December 15 to May 2), cattle were fed corn silage (.03 mg Se/kg) supplemented with either: no protein supplement (control), soybean meal or a urea-corn mixture. Cows and calves receiving Se-E had higher (P less than .01) whole blood glutathione peroxidase (GSH-Px) activity and plasma Se concentrations than controls. Selenium-E injections reduced (P less than .05) calf death losses from 15.3% to 4.2% and slightly increased (P less than .10) adjusted calf weaning weights. Hemoglobin concentrations were higher (P less than .05) in Se-E-injected supplemented calves at 1 mo of age but not at 5 or 7 mo of age.(ABSTRACT TRUNCATED AT 250 WORDS)