Toxic effects of large amounts of DL-methionine infused into the rumen of sheep.

Four Merino wethers were fed ad libitum on a roughage diet comprised of equal parts of chopped lucerne hay and oaten chaff. The sheep received continuous infusions of DL-methionine into the rumen; the daily dose increasing from 0 g (control treatment) up to 30 g in 3 g amounts at weekly intervals. Dry matter intake (DMI) fell below the control level when 24 g/day or more of the amino acid was infused, while plasma free methionine levels increase substantially when 30 g/day was given. There was no effect of DL-methionine supplementation on the bodyweight of the animals. However, when 30 g/day of DL-methionine was infused one animal died and the acute condition of 2 others necessitated their slaughter. Significant lesions included acute nephrosis and haemolytic anaemia, with milder changes in the liver and pancreas. This report indicates that sheep are unlikely to show the kind of chronic methionine toxicity seen in other species.