Myopathy in cattle induced by alkaloid extracts from Thermopsis montanta, Laburnum anagyroides and a Lupinus sp

A purified alkaloid preparation containing N-methylcytisine, cytisine, 5,6-dehydrolupanine, thermopsine and anagyrine from Thermopsis montana induced prolonged recumbency and microscopic acute hyaline skeletal myodegeneration with myofibre regeneration in cattle similar in type and severity to that induced by Thermopsis montanta plant material. This indicates that the alkaloid(s) of Thermopsis montana are responsible for the myopathy caused by the plant. An alkaloid preparation containing mostly anagyrine from a Lupinus sp. and an alkaloid preparation containing only cytisine from Laburnum anagyroides each caused microscopic skeletal muscle degeneration and necrosis similar to, but less severe than, the alkaloid extract from T. montana, but without clinical recumbency. Dosage and severity of response suggest that neither of those two alkaloids alone can account for the effects induced by Thermopsis. The data suggest that quinolizidine alkaloids with a alpha-pyridone A-ring may be responsible for the lesions and that individual alpha-pyridones may have additive effects.