Abstract
Simple SummaryThe microbiological safety and quality of commercial animal feed for laboratory animals, produced in Costa Rica, was assessed. Analysis of the animal feed included general microbial markers (total coliforms and molds) and the behavior over time of two specific feed contaminants (Salmonella spp. and mycotoxins). Results from the study suggest that there is a low risk of contamination from viable microorganisms but the product contains important levels of mycotoxins. Current preventive measures (UV light disinfection) are not effective and additional handling protocols should be considered.Safety and quality of compound feed for experimental animals in Costa Rica is unknown. Some contaminants, such as Salmonella spp. and mycotoxins, could elicit confounding effects in laboratory animals used for biomedical research. In this study, different batches of extruded animal feed, intended for laboratory rodents in Costa Rica, were analyzed to determine mycotoxin and microbiological contamination (i.e., Salmonella spp., Escherichia coli, total coliform bacteria, and total yeast and molds enumeration). Two methods for Salmonella decontamination (UV light and thermal treatment) were assessed. Only n = 2 of the samples were negative (representing 12.50%) for the 26 mycotoxins tested. Enniatins and fumonisins were among the most frequent toxins found (with n = 4+ hits), but the level of contamination and the type of mycotoxins depended on the supplier. None of the indicator microorganisms, nor Salmonella, were found in any of the tested batches, and no mold contamination, nor Salmonella growth, occurs during storage (i.e., 2–6 months under laboratory conditions). However, mycotoxins, such as enniatins and fumonisins tend to decrease after the fourth month of storage, and Salmonella exhibited a lifespan of 64 days at 17 °C even in the presence of UV light. The D-values for Salmonella were between 65.58 ± 2.95 (65 °C) and 6.21 ± 0.11 (80 °C) min, and the thermal destruction time (z-value) was calculated at 15.62 °C. Results from this study suggest that laboratory rodents may be at risk of contamination from animal feed that could significantly affect the outcomes of biomedical experiments. Thus, improved quality controls and handling protocols for the product are suggested.
Highlights
The quality and safety control of the diets for laboratory animals is crucial for the welfare of the animals and to ensure that experimental outcomes are not biased by unintended nutritional or contamination factors [1,2]
The samples were acquired from two different local suppliers (n = 9 and n = 7 different feed batches from suppliers 1 and 2, respectively)
Suppliers 1 and 2 showed n = 2 and n = 1 samples with aw values above 0.60, which would classify them as intermediate moisture foods
Summary
The quality and safety control of the diets for laboratory animals is crucial for the welfare of the animals and to ensure that experimental outcomes are not biased by unintended nutritional or contamination factors [1,2]. Animal feed, or the raw materials used for its fabrication, are prone to contamination, which can occur at any stage of processing or during storage [4]. In Costa Rica, this type of feed usually contains animal (poultry, beef, and pork) by-product meals, which have shown a high prevalence of Salmonella contamination [6,7]. This is important, as foods with reduced aw levels are believed to be less permissive for microbial growth, but some pathogens can survive for extended periods under these conditions [8]
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