Mild mycotoxic nephropathy was induced in 6 pigs by a diet containing ochratoxin A at 800 ppb, several times higher than that naturally encountered in some feed for pig production in Bulgaria. The nephropathy was expressed only as slightly hypertrophied kidneys with a faintly mottled surface, discernible at the end of the experiment to a skilled observer but probably not recognisable in routine slaughterhouse processing. Histological examination showed two types of changes: degenerative - affecting epithelial cells in some proximal tubules of pigs after 6 months, and proliferative changes in the interstitium which predominated after 1 year of exposure to ochratoxin A. Telangiectasis and lymph stasis were rarely seen. The renal lesions were similar to those described for classical mycotoxic porcine nephropathy formerly encountered in Denmark, but they were rather different from the porcine nephropathy which occurs spontaneously in Bulgaria. Measurement of ochratoxin A in serum provided analytical values complementary to feed intake and with similar concentration values. It also showed both accumulation with time, from 3 months to 6 months (approximately 1 ppm), and a 2-fold range of values within a group eating from a common feed source, as in commercial pig production. Mild symptomatology in this long, single-mycotoxin experiment serves to lessen somewhat the current perception of the direct renal toxicity of ochratoxin A alone, though a role in multi-toxin contexts is unquestioned.
Microflora of more than 100 samples of different sorts of foodstuff (coarse fodder, grain forage, mixed fodder, premixes, silo, whole milk substitute etc.) selected in 1989-1992 in the period of mass diseases and death of animals in farms of Ukraine has been studied. It is shown that the amount of spore material included in lg of fodder, depends on the sort of feed substrate. Grains and grain forage (94.5 thou. spores in 1 g) occupy the first place in sporification with fungi; vetch-oat mixture and whole milk substitute (82-89 thou. spores)--the second place; mixed fodder granules and maize briquettes (79.5-66.5 thou. spores)--the third place; the latter are mixed fodder plants hay, cereals straw (11.8-43.5 thou. spores). Aspergillus mainly occurred on the concentrated forage, grain, grain forage, in less amount--in grass stand, cereals straw. Penicilli, fusari and other species of saprophytic fungi dominated on hay of natural meadows, on mixed fodder plants and cereals straw. It has been stated that the highest toxicity was typical of the fodder samples infected with Aspergillus strains producing kojic acid. Under conditions of our experiments out of 67 strains of genus Aspergillus kojic acid was synthesized by 48.6% of the total number of the tested fungus cultures. The greatest number of kojic acid producers was found among Aspergillus flavus isolates (56.8%) the less number--among A. fumigatus (36.7%). Kojic acid has been revealed to exert a pathological effect on the organism of different animal species.