Muller HM, Amend R.
Department of Animal Nutrition, University of Hohenheim, Stuttgart, Germany.
Maize silage was inoculated with Penicillium roqueforti strains which are able to form the mycotoxins mycophenolic acid (MPA), patulin (PAT), penicillic acid (PA), or PR toxin (PRT). The silage was incubated for 160 d without agitation under aerobic conditions at 15 degrees C in the dark. The mycotoxins were quantified by HPLC and identified by HPLC combined with diode array detection and by two-dimensional thin layer chromatography. MPA, PAT, PA, and PRT above the detection limit were measured for the first time at 36, 22-27, 13, and 49 days of incubation, maximum toxin contents (mg/kg) were 3.56 MPA, 15.10 PAT, 3.06 PA, and 2.17 PRT. With increasing storage time toxin contents decreased to a low or non detectable level. The production of MPA, PAT and PRT was preceded by an increase in pH from 4 to 8-9. Along with the initial pH increase the content of ergosterol as well as of P. roqueforti and yeast propagules increased whereas the levels of total soluble sugar and of water extractable NH3 decreased. It is concluded that the probability to detect MPA, PAT, PA, and PRT in maize silage moulded by P. roqueforti under practical conditions of agriculture is low during the growth of this fungus and again after prolonged storage.
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