COMPARITIVE TOXICITY AND METABOLISM OF PYRROLIZIDINE ALKALOIDS IN RUMINANTS AND NONRUMINANT HERBIVORES

Abstract

The toxicity of tansy ragwort (Sencio jacobaea) to several ruminant and nonruminant species was tested. Cattle and horses were susceptible (lethal dose of tansy ragwort (TR) was 4–8% of body weight) whereas sheep and goats were resistant (lethal dose of TR was 200–300% of body weight). Other nonruminant herbivoires (rabbits, gerbils, guinea pigs, hamsters) were resistant to TR. Incubation of TR in sheep rumen fluid did not alter its toxicity to rats. No 1-methylene pyrrolizidine alkaloid (PA) derivatives were detected in TR incubated in sheep rumen fluid. The activities of PA-metabolizing enzymes in sheep liver were not influenced by dietary TR. Key words: Pyrrolizidine alkaloids, ruminants, nonruminant herbivores