Study of mycotoxins in animal feeding stuffs has concentrated on the occurrence of aflatoxins and, to a lesser extent, other mycotoxins in cereals, raw materials and concentrate feeds. However, ruminant diets contain a high proportion of forage crops such as grass or maize silage, hay and straw. Under adverse growing, production or storage conditions, fungal spoilage is likely to occur with some degree of mycotoxin contamination. The mould flora of forage crops is likely to differ significantly from that of cereals and mycotoxin contamination, should it occur, could differ qualitatively and quantitatively. Information relating to forage crops as a potential source of mycotoxins is reviewed. Some field incidents and animal disease which may be mycotoxin related are discussed and analytical methods are reviewed. Information on dose and effect of candidate mycotoxins is given where available. The review suggests areas which the authors consider merit further study. Crown Copyright 1998.

The commercial processing of oats is different from that of other cereals, such as wheat and maize. In northwest Europe, oats also appear to be more susceptible to contamination with HT-2 and T-2 toxins than other cereals. Mycotoxins, such as deoxynivanol and zearalenone, in cereals are already controlled by EU legislation. With regard to additional, impending legislation, this study examined HT-2 and T-2 toxins together with zearalenone, deoxynivalenol and other related toxins in a commercial oat mill and how the concentrations varied from raw oats to the final prepared oat flakes. Concentrations of each Fusarium mycotoxin fell by 90-95% during the process, with the major loss being a physical distribution occurring at the de-hulling stage. Initial studies of losses occurring at other stages, such as kilning or de-branning of prepared oat groats, suggest these to be small. The use of colour sorting after kilning showed higher concentrations of each mycotoxin in the discoloured groats. The feasibility of developing a predictive tool for the oat industry is examined.

Batches of whole wheat contaminated with ochratoxin A were produced by inoculation with Penicillium verrucosum under controlled conditions in the laboratory. The fate of ochratoxin was followed through initial cleaning, abrasive scouring of the outer grain coat, milling into wholemeal wheat or into 10 milled fractions. Bread was baked from both wholemeal flour and straight-run white flour. Concentrations of ochratoxin A in the cleanings, scourings, and the bran and offal fractions were increased, but reduced in the white flour. Scouring removed up to 44% of the ochratoxin A present, but only a small further loss occurred in the bread-making process. An overall reduction of about 75% could be achieved in white bread using a combination of cleaning scouring and removal of the bran and offal fractions. Maximum overall reduction in producing wholemeal bread was about 40%. The reduction in ochratoxin A that can be achieved must be considered in relation to economic constraints concerning the disposal of wasted grain. Appropriate strategies for the use or disposal of potentially highly contaminated cleanings, scourings, bran or offal must be established.

This survey examined 140 samples of raw maize as received at ports or at major maize mills in the UK and 12 after initial cleaning. Samples were examined for aflatoxins B1, B2, G1 and G2, ochratoxin A, zearalenone and fumonisins B1, B2 and B3 using fully validated analytical HPLC methods with detection limits of 0.1 microgram/kg for each aflatoxin and ochratoxin A, 4 micrograms/kg for zearalenone and 10 micrograms/kg for each fumonisin. 95.0% and 92.1% of samples met the new EC statutory maximum permissible level for total aflatoxins and aflatoxin B1 respectively. The maximum concentration of ochratoxin A found was 1.5 micrograms/kg. Zearalenone and fumonisins were detected in almost every sample with 41.7% of maize containing more than 100 micrograms/kg of zearalenone and 48% of samples containing more than 1000 micrograms/kg total fumonisins. Initial cleaning of raw maize reduced aflatoxin concentrations by about 40% and total fumonisins by 32%.

Examination of 330 samples of animal feed ingredients for the presence of a number of mycotoxins has been carried out. These samples were drawn from 186 animal feed mills in the United Kingdom. Aflatoxin B1 was the mycotoxin found most frequently, occurring in most samples of rice bran, maize products, palm kernels and cottonseed, but not in only 3 out of 20 samples of sunflower, in 1 out of 20 samples of soya and in no samples of peas, beans or manioc. Analytical difficulties were met with some combinations of commodity and mycotoxin and all results are uncorrected for recovery. The highest level was detected in a sample of maize gluten: 41 micrograms/kg of aflatoxin B1 (47 micrograms/kg total aflatoxins). Maize products also frequently contained fumonisins B1 and B2 at levels up to nearly 5,000 micrograms/kg in total and zearalenone up to a maximum level of 500 micrograms/kg. Ochratoxin A and citrinin were found in approximately 20% of wheat and barley samples. One sample of barley contained ochratoxin A at a level of 102 micrograms/kg and citrinin at a level of 8 micrograms/kg. Low levels of ochratoxin A also occurred in a few samples of other ingredients: rice bran, palm kernel and beans. Sterigmatocystin at 18 micrograms/kg was found in one sample of organically grown wheat and a trace amount of zearalenone in one sample of manioc. Multi-mycotoxin contamination also occurred, particularly in some samples of maize for which 19 out of 50 samples contained both aflatoxins and fumonisins.

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Extrusion technology is used widely in the manufacture of a range of breakfast cereals and snacks for human consumption and animal feeds. To minimise consumer exposure to mycotoxins, the levels of deoxynivalenol (DON) and zearalenone (ZON) in cereals/cereal products and fumonisins B(1) and B(2) (FB(1) and FB(2)) in maize are controlled by European Union legislation. Relatively few studies, however, have examined the loss of Fusarium mycotoxins during processing. The behaviour of FB(1), FB(2) and fumonisin B(3) (FB(3)), DON and ZON during extrusion of naturally contaminated maize flour and maize grits is examined using pilot-scale equipment. DON and ZON are relatively stable during extrusion cooking but the fumonisins are lost to varying degrees. There is some loss of ZON when present in low concentrations and extruded at higher moisture contents. The presence of additives, such as reducing sugars and sodium chloride, can also affect mycotoxin levels. Moisture content of the cereal feed during extrusion is important and has a greater effect than temperature, particularly on the loss of fumonisins at the lower moistures. The effects are complex and not easy to explain, although more energy input to the extruder is required for drier materials. However, on the basis of these studies, the relationship between the concentration of Fusarium toxins in the raw and finished product is toxin- and process-dependent.