Feed refusal factors in pure cultures of Fusarium roseum 'graminearum'.

Isolations from 1972 Wisconsin feed refusal corn yielded predominantly cultures of Fusarium roseum 'graminearum.' With one possible exception, none of the selected isolates of this fungus induced emesis in pigeons, whereas six of nine isolates produced feed refusal responses in all test animals. A single isolate of F. roseum 'equiseti' also induced a severe refusal response and possibly slight emesis. None of the other fungi isolated from this corn (F. moniliforme, Acremoniella atra) or controls caused either emesis or feed refusal. Zearalenone was detected in all isolates and was shown to be partially responsible for refusal activity. The remaining activity was ascribed to one or more nonvolatile, neutral, relatively polar molecules. T-2 toxin, although not detected in these isolates, was shown to have dramatic refusal activity in rats.