Even if dairy cattle drink water polluted by toxic blue-green algae, the toxins do not get into their milk -- which remains safe for human consumption.
"Many rural water bodies, including farm dams, can be affected by blooms of blue-algae which can produce a variety of potentially fatal toxins," says CSIRO's Dr Gary Jones.
It is not uncommon for livestock to drink non-lethal doses of algae from these dams, raising the question of whether the toxins can contaminate our 'clean-green' agricultural products and present a health risk. This possibility was raised in a report to the Prime Minister's Science and Engineering Council in 1996.
Research by scientists from CSIRO Land & Water and CSIRO Tropical Agriculture has shown there is little risk from one of these algal toxins contaminating Australian dairy products. Whilst this is good news for the dairy industry, it may not be the case for other toxins or other agricultural products.
"Our research was intended to find out whether one particular toxin could get into dairy products, especially milk." says Mr Phillip Orr. "The good news is that it can't."
To test the theory, dairy cows were fed water contaminated with a typical bloom concentration of the blue-green algae Microcystis. This produces a potent toxin known as microcystin that can cause liver damage and cancer if consumed in sufficient amounts. The World Health Organisation recently advised an absolute limit of one part per billion of microcystin in human drinking water.
"In this instance, not only did the cows themselves show no ill effects from drinking this contaminated water, but we could not even detect trace amounts of microcystin in their milk using two highly-sensitive tests," Mr Orr reported.
"This is very reassuring for the dairy industry, and for consumers," says Dr Hunter. "We consider it to be good evidence that cows which have consumed water or feed contaminated with microcystin produce milk which is either free of the toxin or has levels so low that it presents no threat to our health."
Materials provided by CSIRO Australia. Note: Content may be edited for style and length.
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