Neuropathological effects and deaths of cattle and sheep in Argentina from Phalaris angusta.

Neuropathological disorders and mortality occurred in cattle and sheep grazing P angusta. This native plant of South America is frequently found as a good quality component of natural pastures. Cattle and sheep feeding in pastures where P angusta was dominant started dying or showing signs 3 to 5 d after rain-falls started following a period of drought. Some animals died suddenly, while others nervous effects( incoordination, inability to walk normal, recumbency) and death for up to 2 w after the beginning of the signs. Postmortem findings were bilaterally symmetrical, greenish pigmented areas in the grey matter of the brain stem and diencephalon. A greenish tinge was also noted between the cortex and the medulla of the kidneys. Granules of a brown pigment were noted within the cytoplasm of neurons. An alkaloid substance was detected in the plant. Morbidity was 2.3 to 10.5% in herds B and A, and 0 to 3.4% in flocks D and C, respectively. Mortality was 0.8 to 1.0% in herds B and C, and 3.4 to 11.7% in flocks D and C, respectively. P angusta behaves, in terms of toxicity, as other Phalaris spp. Its widespread distribution in areas of extensive grazing poses a threat to cattle and sheep production in Argentina.