Amaranthus retroflexus (redroot pigweed) poisoning in cattle.

Amaranthus retroflexus (redroot pigweed)-induced nephrotoxicity was diagnosed in 6 herds of cattle from 3 counties in southwest Missouri. Forty-eight cows and calves died and another 35 were clinically affected. Serum urea nitrogen concentration, determined in 4 affected calves, was between 55 and 284 mg/dl, and serum creatinine concentration was between 6.