PRODUCTION AND GLUTATHIONE RESPONSES TO RUMEN-PROTECTED METHIONINE INYOUNG SHEEP GRAZING DRY PASTURES OVER SUMMER AND AUTUMN

The aims of the experiment were to evaluate, in weaner sheep grazing d ry annual pastures, the production responses and changes in blood and tissue glutathione concentrations to a methionine formulation (Lactet) protected from microbial breakdown in the rumen. Two groups of 60 wea ner wether sheep, weighing 32.8 kg, were supplemented with lupin grain containing either nil (control) or 9g Lactet per day. Lactet provided 3g of protected methionine per day. The sheep grazed dry pastures and were rotated through 2 plots every week from December to June. After June the treatment ceased and the sheep grazed as one group until shea ring in September. The sheep given Lactet grew 340g more clean wool wi th a greater fibre diameter (1.2 mu m) than the control sheep. Lactet supplementation increased liveweights during treatment and for 3 month s following treatment. Faecal dry matter output was significantly incr eased by Lactet supplements and the effects were maintained in the pos t-treatment period, indicating that Lactet supplementation increased d ry matter intake. Glutathione concentrations were significantly increa sed in whole blood, liver, and muscle but not in skin. Changes due to season were greater than changes due to treatment. It was concluded th at glutathione in blood or tissues; although responsive at times, was not a reliable indicator of sulfur amino acid intake or status. Signif icant increases in total body water, protein, ash, fat, and total body energy were observed relative to the control group following Lactet s upplementation. We conclude that young sheep grazing dry annual pastur es in summer and autumn have the potential to respond to supplements o f rumen-protected methionine even at low energy intakes from low quali ty pastures and show improvements in wool quality and quantity as well as liveweight and intake.