Aflatoxin poisoning and contaminant issues in production animals
Aflatoxin is produced by moulds growing on grain and nuts, particularly on peanuts and corn (maize). Aflatoxins are a regulated toxin in animal feed worldwide, because these toxins can poison animals if they eat enough. Aflatoxin contamination in food can cause liver cancer in people.
Aflatoxin can be present in:
- peanut by-products
- bakery waste.
The level of contamination increases rapidly if these items are not kept dry in storage.
If you are dealing with animal commodities that have the potential to cause aflatoxin contamination, you are bound by a general biosecurity obligation under the Biosecurity Act 2014 to minimise the impact of the biosecurity risk posed by aflatoxin to human health or trade in agricultural produce.
Limits of aflatoxin B1 in animal feed
Aflatoxin B1 is the main aflatoxin found in crops. You must control the aflatoxin content of dairy feed, as up to 5% of the aflatoxin eaten by lactating animals is passed into their milk.
In Queensland, levels of aflatoxin B1 in certain feeds are restricted. The Code of practice for feed for food producing animals under the Biosecurity Regulation 2016 sets the maximum levels of aflatoxin B1 to:
- 0.02 mg/kg in peanut shell or screenings and peanut meal in feed for dairy animals
- 0.1 mg/kg in other oilseed meals in feed for dairy animals
- 0.2 mg/kg in other feeds for dairy animals
Commodities that can cause aflatoxin contamination
Although a number of food and animal feed commodities can become contaminated with aflatoxin, peanuts and corn present the most serious risks.
Aflatoxin contamination in peanuts
Aflatoxin contamination is a serious problem in peanuts grown in the Burnett region. If you are in the peanut industry, you can use a variety of measures to minimise the aflatoxin content of nuts destined for human consumption.
Levels of aflatoxin can vary between crops and plants because:
- hay derived from irrigated crops produces less aflatoxin
- seasons with mid-to-late droughts often present a high risk in rain-fed crops - which increases contamination
- drought-stressed crops can contain more than 100mg/kg of aflatoxin
- the leaf and stalk contain little toxin, so levels can vary depending on the number of peanut pods.
You can minimise the risk of aflatoxin contamination in milk by:
- limiting peanut meals and peanut hay to
- 10% of the daily diet for dairy cows
- 25% of the total diet for mature beef cattle
- not feeding cattle peanut meals and peanut hay for 2 weeks before sending them to slaughter.
Aflatoxin poisoning has occurred in pigs, calves and, less often, adult cattle.
Aflatoxin contamination in corn (maize) and sorghum
Corn and sorghum can become contaminated, particularly in drought conditions. The concentrations present at harvest are usually not enough to poison production animals. But if the grain is damp or not aerated properly, aflatoxin can rapidly increase in hot spots in storage.
Aflatoxin contamination in other crops
Other crops, such as wheat, barley and oilseeds, can be contaminated with aflatoxin if they become mouldy in storage. The contamination levels in these crops is much less than the levels in peanuts and corn.
Minimising aflatoxin contamination in meat and milk
The risk to the health of production animals is generally quite low if grain and mixed feeds are stored properly. The risk increases during droughts when the aflatoxin content of some crops increases and more crop by-products are fed to production animals.
Cattle that eat large quantities of grain are at a slightly higher risk of having aflatoxin residues in the offal. The animal remains contaminated for 1-2 weeks.
Grass, silage and pasture hay do not contain aflatoxin. When you purchase grain or mixed feed, ask for a commodity vendor declaration. This is written assurance from the supplier that the grain or feed meets regulated standards for aflatoxin.
Managing aflatoxin levels in dairy cattle
Consumer concern about food safety and contaminants in general is increasing. The dairy industry conducts aflatoxin testing of milk as part of the Australian Milk Residue Analysis (AMRA) survey. The sensitivity of tests that detect contaminants is rapidly increasing. Aflatoxin contamination is not destroyed by milk pasteurisation and will transfer into powdered milk, yoghurt, and other milk-based products.
Milk contamination could have severe economic consequences for you - the farmer - and the industry as a whole. To minimise the risk you should:
- limit the use of peanut meals and their by-products in dairies
- ensure feed grain is stored in conditions that avoid mould growth
- harvest grain at the recommended moisture content, dry if necessary, and maintain good aeration and insect control
- regularly clean feed bins.
Pasture-based beef, sheep and dairy production systems have a low risk because aflatoxins are not produced in pasture, grass hays and silage.