Aflatoxins are a risk to human health, being a known cancer-causing agent, and cannot be destroyed through processing, including pasteurisation.
The dairy giant has told farmers to step feeding it until a code of practice is in place to ensure that the copra meal supplied to dairy farmers contains fewer than five parts per billion of aflatoxins.
Fonterra said farmers intending to use compounded feeds that contain copra should ensure that the meal does not make up more than 15 per cent of the product, and that they request the supplier provide laboratory results showing levels of aflatoxins below five parts per billion.
Contamination by aflatoxins usually results from excessive moisture levels at some stage during harvest or storage, causing the growth of moulds that release the toxins.
Copra meal is made from coconut kernels and is a good source of oils and protein. Its use by dairy farmers has declined in recent years, with processed palm kernel now far more popular. This is unaffected by the ban.