RESPONSES IN WOOL GROWTH, LIVEWEIGHT, GLUTATHIONE AND AMINO-ACIDS, INMERINO WETHERS FED INCREASING AMOUNTS OF METHIONINE PROTECTED FROM DEGRADATION IN THE RUMEN

The aim of the experiments reported was to evaluate the protection fro m microbial breakdown of two methionine formulations (Lactet and Mepro n) and to measure responses in wool production, liveweight, amino acid s and glutathione in blood and tissues when one of these forms of meth ionine (Lactet) was supplied to merino wethers fed at maintenance. Lac tet was well protected against microbial breakdown in the rumen. Peak values for concentrations of methionine in plasma, following administr ation of the different forms of methionine into the rumen, were 574, 1 48 and 143 mu mol L(-1) for Lactet, DL-methionine and Mepron. Producti on responses to dosed levels of Lactet (0, 1, 2, 3, 5, 8 g methionine day(-1)) were measured over 63 days in the animal house. Significant l inear responses were obtained for wool growth (4-38%), fibre diameter (0.5-2 mu m) and liveweight gain (30-115%). Concentrations of reduced glutathione in blood, liver and skin were increased, at some times dur ing the experiment, by provision of Lactet. However, responses were in consistent and highly variable among sheep. Glutathione was of limited use as an indicator of sulfur amino acid intake or status. Sulfate in plasma increased markedly at all levels of Lactet intake, and there w as a linear relationship between Lactet intake and the concentration o f sulfur in wool. Plasma free methionine and the ratio of methionine t o total essential amino acids showed significant linear responses to t he supplements. It was concluded that Lactet was an effective method o f supplying rumen-protected methionine to ruminants.