Analysis of the mycotoxins of fusarium

Abstract

Fusarium contamination of maize has been shown to be a problem in Zambia. In this study it was decided to test for the presence of five toxins produced by Fusarium; Zearalenone, T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON) and nivalenol, in maize and maize products. This was the first major study involving the analysis of trichothecenes in Zambia, and thus several methods of extraction and determination of the fo,ur tricho-thenes and Zearalenone in maize and mixed feeds were tested, in order to arrive at the most suitable methods for use in our Laboratory. The methods finally adopted gave 80, 80,86, 50 and 60 per cent recoveries of added Zearalenone, DON, nivalenol, T-2 toxin and DAS respectively. TLC was used for qualitative as well as quantitative determination of the toxins and as low as 50 (jg/kg Zearalenone, 80 |jg/kg DON and nivalenol, and about 2000 pg/kg T-2 toxin and DAS could be determined. Mouldy maize, rejected by NAMBOARD but mostly used by farmers as animal feed supplement or in the brewing of local opaque beer, was collected from farmers around Lusaka and analysed for the five Fusarium toxins. This maize was found to contain only Zearalenone and DON in the range of 0.08-6.0 mg/kg and 0.5-16 mg/kg respectively. A year long survey of mixed animal feeds from National Milling Company was initiated and 148 samples were analysed for Zearalenone, DON and nivalenol. 17 per cent of the samp¬les contained Zearalenone (0.05-0.6 mg/kg) and 1.4 per cent of the samples contained DON (1.0 mg/kg). No nivalenol was detected in any of the samples. The Zearalenone and DON positive samples were further tested for T-2 toxin and DAS but none was detected. This is the first report of the natural occurrence of Zearalenone and DON in mixed feed samples in Zambia. An isolate of F. graminearum was gro.wn at 26 C and 16°C corresponding to average maximum and minimum temperatures often recorded near the end of the rainy season. Zearalenone production was found to be favoured by low temperatures (16 C) while DON production was found to be favoured by high temperatures (26 C ).