Histological and ultrastructural lesions of acute tubular necrosis in beef cattle with Amaranthus hybridus-induced nephrotoxicity.

An outbreak of poisoning associated with glyphosate-resistant Amaranthus hybridus affected three cows and twenty-five calves in Tacuarembó, Uruguay. The disease occurred from summer to autumn, coinciding with plant fruiting. Affected calves showed nasal discharge, preputial edema, weakness, recumbency, and gross lesions compatible with renal failure. Histological and ultrastructural analyses demonstrated acute tubular necrosis in proximal convoluted tubules and the descending limb of loops of Henle, supporting a direct toxic effect of Amaranthus-derived compounds in affected calves.