Production responses of sheep supplemented with copper, cobalt and selenium on kikuyu ryegrass pastures.

The copper (Cu) and selenium (Se) status of SA Mutton Merino ewes grazing kikuyu-ryegrass pastures was investigated by analysing blood and liver samples. The response of ewes to oral supplementation with Cu, Cobalt (Co) and Se as single elements, or in 4 combinations were simultaneously assessed in a 2 x 2 x 2 factorial experiment. Pastures grazed were low in Cu (less than 5 mg Cu/kg DM) except for the summer months, while pasture Se concentrations remained at concentrations less than 0,03 mg Se/kg DM for almost the entire period. Plasma Cu concentrations remained in excess of 80 micrograms/dl until pasture Cu concentrations decreased below 5 mg/kg DM. Blood Se concentrations generally reflected liver Se concentrations. Supplementation of ewes with 5 g Cu oxide needles (Embamin Copper LA, Rhône Poulenc) markedly increased (P < or = 0,01) hepatic Cu and plasma Cu concentrations. The monthly drenching of ewes with 5 mg Se as sodium selenite elevated blood Se concentrations to normal levels in excess of 100 ng/ml while ewes not supplemented with Se had blood Se concentrations indicative of a deficiency (50-100 ng/ml). Supplementation of ewes with Cu and Se elevated (P < or = 0,05) concentrations of these trace elements in the plasma and blood of their progeny. Supplementation of ewes with Cu and Se resulted in respective improvements (P < or = 0,05) of 5,3 and 4,8% in live mass during lactation, compared to contemporaries which did not receive either Cu or Se.(ABSTRACT TRUNCATED AT 250 WORDS)