THE SULFUR AND SELENIUM STATUS OF PREGNANT EWES GRAZING MEDITERRANEANPASTURES

Sheep require both sulfur and selenium for normal wool growth and to p rotect against diseases caused by free radical damage. This work descr ibes this seasonal changes in the concentrations of sulfur, both as gl utathione and inorganic sulfur; and selenium, in pregnant ewes, and th e effects thereon of a multi-element supplement containing sulfate, se lenium, and vitamins A and E. Merino ewes (420) were divided into 4 eq ual treatment groups, control (C), vitamins (V), minerals (M), and vit amins plus minerals (V+M), in a 2(2) factorial design. The control gro up was offered a loose salt lick (NaCl) at 175 g/head.day and the mine ral group an equivalent amount of a multi-element mineral mix (Siromin ). The vitamin groups were offered either salt or the mineral mix with added vitamins E and A. Treatments started 3 weeks prior to mating in November and lasted until 1 week prior to lambing in May. Sheep were sampled until weaning in September. Regardless of treatment: the conce ntrations of glutathione in blood and liver declined by 60% and 40%, r espectively, when sheep were grazing dry pasture during summer. Sulfat e-sulfur concentration in plasma of ewes in the C and V groups decline d by 80% in the same period to <10 mg sulfur/L, values indicative of s ulfur deficiency. The mineral supplement (M) increased concentrations of plasma sulfate-sulfur at most sample times, but the VI-M treatment generally did not. Glutathione concentration in blood and tissues show ed little response to supplementary minerals or vitamins. Selenium con centration in blood of ewes was inversely related to the number of yea rs since receiving a selenium pellet. Mean concentration declined to t he deficient range (0.02 mg/L) in spring in C and V ewes. Treatment wi th the mineral mix raised blood selenium concentrations to 0.060 mg/L within 2 months and maintained concentrations above the deficient rang e for several months after cessation of treatment. The results provide evidence of an under supply of sulfur during the dry summer period an d of a need to administer selenium pellets at least twice in the lifet ime of ewes.