Estudo sobre a contaminação com espécies toxígenas, potencialmente produtoras de micotoxinas, em rações destinadas à alimentação de eqüinos

Abstract

Most feedstuffs, cereal crops and other agricultural commodities are very susceptible to contamination by molds able to produce mycotoxins. Mycotoxins are toxic secondary metabolites that can cause adverse effects such as carcinogenesis, teratogenesis, nephrotoxicity and immunosuppression, leading to numerous pathologies and consequent economic losses. Aspergillus, Penicillium and Fusarium are the most frequently genera involved in animal and human cases of mycotoxicoses. In equines, mycotoxicoses are mainly related to corn based feedstuffs consumption contaminated with fumonisins (FBs) produced by F. verticillioides. These mycotoxins are responsible for equine leukoencephalomalacia (ELEM), an acute and fatal neurological disease characterized by neurotoxic symptoms. More than one mycotoxin may exist simultaneously in a particular commodity or ingredient. Generally, the effects of these toxins tend to add up in synergic response, increasing the risk and hazard to animal health and productivity. Aflatoxins (AFs) are mycotoxins produced by A. flavus and A. parasiticus. Aflatoxin B1 (AFB1) is the most frequently detected and it has been described as the strongest biologically synthesized hepatocarcinogenic substance that can affect humans and animals. Checking the mycological and mycotoxicological quality, control of feedstuffs and commodities destined to equine consumption is critical for improving animal production and performance. The purposes of this study were: 1) to determine the occurrence of Aspergillus spp., Penicillium spp. and Fusarium spp., 2) to detect and quantify FB1 and AFB1 in equine feedstuffs. Sixty samples from different commercial feeds, oats and farm-made feeds were randomly collected from different studs located in Rio de Janeiro and Seropédica, from June 2003 to June 2006. Analysis of the mycobiota was made by the plate dilution spread method onto dichloran rose bengal chloranphenicol agar (DRBC), dichloran glycerol 18% agar (DG18) and Nash-Snyder culture media. Total fungal counts were expressed as CFU/g. The isolation frequency (%) of fungal genera and relative density (%) of fungal species were determined. Mycotoxins determination was done using commercial ELISA kits (Beacon Analytical Systems Inc.). Total fungal counts were similar on both DRBC and DG18 media. The highest counts were from oats and farm-made feeds. Aspergillus (43%), Penicillium (26%) and Fusarium (11%) were the most frequently isolated genera. Aspergillus niger (27%), A. flavus (25%), Penicillium corylophilum (19%), P. fellutanum (14%) and Fusarium verticillioides (100%) had the highest relative densities. Seventy five percent of the samples showed FB1 contamination with range from not detected to 8.5 μg.g-1. Only two samples were negative for AFB1 contamination with range from 0.5 to 99.4 μg.kg-1. It is recommended that contaminated corn or corn by-products be limited to no more than 20% of the diet for equids. Even if the amount of mycotoxins produced is not enough to cause adverse effects in animals, it is a sign that the feed will be less nutritious. It is also necessary to establish maximum limits of fungal counts for potential AFs and FBs species.