Comparison of the fungal contamination in Rainbow trout feed in farms located in fields and mountains

Introduction: The consistent increase in aquatic consumption due to the limitation of marine resources has led to aquaculture development in the sea and on land. Mold contamination of feed decreases feed's nutritional and health quality by changing the composition of nutrients and producing mycotoxin. This study aimed to investigate the fungal contamination of rainbow trout in farm storage of six provinces including Kermanshah, Alborz, Qazvin, Lorestan, Tehran, and Mazandaran. The feed samples were contaminated with aflatoxigenic species at a rate of 78.57%, and the abundance of these species was 22.79%. Materials and methods: After sampling the feed and preparing serial dilutions, surface culture was carried out in YGC medium and the total number of fungal colonies was counted. The genus and species of fungi were identified based on macroscopic and microscopic morphology and biochemical tests. The number of fungal colonies in all samples was lower than the standard level, and a total of 158 fungal isolates from 16 genera were obtained. The feed samples were discovered to be contaminated with the Aspergillus genus at a prevalence of 90.47% and an abundance of 70.25%. Results: The fungal species A. niger and A. fumigatus were found to have the highest contamination levels of 80.95% and 66.66%, respectively in feed samples. These species also comprised 21.52% and 17.72% of the fungal population in the feed. Contaminations of feed samples with Fusarium species and Penicillium species were 4.76% and 23.8%, and their abundance were 1.26% and 6.32%, respectively. Contamination with A. fumigatus, Fusarium species, and Penicillium species were higher in farms located in the plains. Conclusion: Based on the research findings, it is revealed that despite the low number of fungal species in the feed samples, the highest abundance and percentage of contamination is related to the Aspergillus genus, especially species with the capability to produce both aflatoxin and ochratoxin.