Effect of Aflatoxins on Animals Milk
What are Aflatoxins?
The aflatoxins are a group of chemically similar toxic fungal metabolites (mycotoxins) produced by certain moulds of the genus Aspergillus growing on a number of raw food commodities. Aflatoxins are highly toxic compounds and can cause both acute and chronic toxicity in humans and many other animals.
Animals are variably susceptible to aflatoxins, depending on such factors as age, species, breed, sex, nutrition, and certain stresses. Swine, cattle, and poultry are the domestic species of greatest economic concern in terms of aflatoxicosis.
In all species, the evidence of disease is a general unthriftiness and reduction in weight gains, feed efficiency, immunity, and production. More conclusive evidence of aflatoxin involvement in disease includes acute to chronic liver disease with concomitant increases in specific liver enzymes in the serum.
In cattle, milk production is affected, but of greater significance is that the aflatoxins in feeds can be rather efficiently converted to toxic metabolites in milk, with even small amounts being readily detectable. The poultry industry probably suffers greater economic loss than any of the livestock industries because of the greater susceptibility of their species to aflatoxins than other species.
Aflatoxins are toxic metabolites produced by certain fungi in/on foods and feeds. They are probably the best known and most intensively researched mycotoxins in the world. Aflatoxins have been associated with various diseases, such as aflatoxicosis, in livestock, domestic animals and humans throughout the world. The occurence of aflatoxins is influenced by certain environmental factors; hence the extent of contamination will vary with geographic location, agricultural and agronomic practices, and the susceptibility of commodities to fungal invasion during preharvest, storage, and/or processing periods.
Aflatoxins have received greater attention than any other mycotoxins because of their demonstrated potent carcinogenic effect in susceptible laboratory animals and their acute toxicological effects in humans. As it is realized that absolute safety is never achieved, many countries have attempted to limit exposure to aflatoxins by imposing regulatory limits on commodities intended for use as food and feed.
There are four major aflatoxins: B1, B2, G1, G2 plus two additional metabolic products, M1 and M2, that are of significance as direct contaminants of foods and feeds. The aflatoxins M1 and M2 were first isolated from milk of lactating animals fed aflatoxin preparations; hence, the M designation. Whereas the B designation of aflatoxins B1 and B2 resulted from the exhibition of blue fluorescence under UV-light, while the G designation refers to the yellow-green fluorescence of the relevant structures under UV-light.
These toxins have closely similar structures and form a unique group of highly oxygenated, naturally occuring heterocyclic compounds.
How much aflatoxin B1 is carried-over to milk?
The carry over rate of aflatoxins from contaminated feed into milk in dairy cows is considered to average 1–2%. However, in high yielding cows, which consume significant amounts of concentrated feeds, the carry over rate of aflatoxin M1 into milk can reach 6.2%.
Practical considerations
Thus, when aflatoxin M1 is detected in milk at elevated levels, there are two practical ways to combat this problem: 1) the contaminated feed should be replaced with aflatoxin-free feed, or 2) an aflatoxin-deactivating agent should be added in the existing feed. Such product should be not only safe and effective, but it should contain only components permitted by legislation.
Economic Impact of Aflatoxins
The economic impact of aflatoxins derive directly from crop and livestock losses as well as indirectly from the cost of regulatory programs designed to reduce risks to animal and human health. The Food and Agriculture Organization (FAO) estimates that 25% of the world’s food crops are affected by mycotoxins, of which the most notorious are aflatoxins.
Aflatoxin losses to livestock and poultry producers from aflatoxin-contaminated feeds include death and the more subtle effects of immune system suppression, reduced growth rates, and losses in feed efficiency. Other adverse economic effects of aflatoxins include lower yields for food and fiber crops .
In addition, the abilitiy of aflatoxins to cause cancer and related diseases in humans given their seemingly unavoidable occurrence in foods and feeds make the prevention and detoxification of these mycotoxins one of the most challenging toxicology issues of present time.
