عنوان مقاله [English]
Introduction About 500,000 species of fungi have been realized up to now. There are abundant fungi in air, soil and our environment. So the growth of them increases in the presence of air moisture and appropriate temperature. However saprophytic fungi have a wide distribution in nature, they are responsible for decomposition of organic materials and playing an important role in the biogeochemical cycles of major nutrients. Some saprophytes are toxic that contaminate human foods and animal feeds by production of mycotoxins. Aflatoxins are the most common and dangerous mycotoxins produced by few species of Aspergillus and penicillium. This group of mycotoxin has disorder and risks, including the induction of liver cancer. They are mutagenic and teratogenic. Aflatoxin B1, B2, G1 and G2, which are naturally produced by several toxic fungi, may contaminate a wide range of dairy animal feeds resulted severe economic loss of cattle meat. Since Aflatoxin B1 and B2 can be transmitted via mammalian’s milk and cheese in form of synthetic Aflatoxin M1 and M2 to human consumers, cause significant health problems. Therefore contamination of animal feed with common toxic airborne saprophytic fungi is a major concern of health officials. Wheat, barley, corn, soybean and other animal feeds may be contaminated with toxic fungi during implantation, harvesting and storage. There are many dairy and livestock centers in Yazd that prepare milk and dairy products for Yazd and neighboring provinces. The aim of current study was to evaluate the amount and type of fungal contaminates of dairy feeds in Yazd dairies.
Materials and methods This cross-sectional descriptive study was conducted in the summer of 2012 on 23 dairies in Yazd. Samples of different animal feeds including concentrates, wheat straw, hay, corn, silage corn, soybean and canola as well as waste of bread, were randomly selected from their bulks. The temperature and humidity of feed storage were recorded by using thermometer and portable hygrometer at the time of sampling. Samples were transferred to medical mycology laboratory in paramedical school by sterile containers. Samples were cultured on Sab ouraud dextrose agar plates based on standard method. Isolated fungal colonies were firstly enumerated and identified using macroscopic and microscopic characteristics for determination of their genus and species of saprophytic and toxic fungi. The suspected fungi with definitive diagnosis by the use of the men tioned methods were then identified by performing slide culture by Riddle method. For the detection of aflatoxin producer species UV radiation was used. Results were analyzed statistically by Chi-square and Mann-Whitney test using SPSS 16 software.
Results and Discussion Saprophytic hyphomycets including Cladosporium, Alternation Penicilium, Verticillium, Aspergillus, Penicillium species and yeast were the most prevalent isolated fungi from cattle feeds in current study. Bread waste showed maximum contamination with opportunistic fungi such as Mucor and Rhizopus species, other saprophyte moulds and yeasts. Wheat straw had the highest contamination of aflatoxin-producing toxic fungi particularly Aspergillus flavus. Silage and concentrate were ranked as highest average contamination with 42600 and 40600 CFU/g, respectively in present study. There was seen a significant relationship between the average humidity of the environment of open and covered storage of feed with frequency of isolated fungal species (P< 0.001). In indoor environments, the humidity was higher than outdoors, and this is one of the factors effecting the increase aggregation in animal feeds stored in indoor storages. Results of present study were supported by similar previous studies that can be beneficial for the man agement of cattle feeds and public health surveillance particularly in disorders of aflatoxin.
Conclusion According to results of present study, there are a high fungal contamination in cattle food with saprophytic and toxigenic fungal spores. Monitoring of animal feed and control of humidity can control the proliferation of micro-organisms in food, eliminate contamination of microorganisms and prevent cross-contaminations. High levels of fungal contamination in intake dairy feed shows that the major source of contamination seems to be in raw materials used for animal feed. With respect to the effect of cattle food contamination especially contamination with Aspergillus flavous on health of cattle and dairy products and the secondary effects on human health, Control of fungal contamination in livestock foods is the best way to prevent aflatoxin contamination in milk and other dairy products, which help to improve the public health.