A shipment of Australian sheep destined for the Middle East has been delayed after it was confirmed that animal rights activists had laced the animals' food with ham in a bid to make them unsuitable for Muslim countries.
Australia's live export trade earns it US$700m a year
Australian Veterinary Officer Dr Hugh Millar said a "shredded, ham-type material" had been found in a feedlot at Portland, Victoria.
It was not immediately clear how many of the shipment's 50,000 sheep had been exposed to the contaminated food.
Under Australia's livestock rules, sheep that have been fed animal products are no longer judged fit for human consumption.
Police said they had arrested a 40-year-old man in connection with the incident.
Animal Liberation, a group which believes the conditions animals are shipped in is cruel, had said it added the pig products on Tuesday night.
The latest incident follows a recent debacle during which 50,000 sheep were stranded for 11 weeks in the Middle East after the country they were bound for, and several other states, refused to receive the animals for health reasons.
The Australian Government was eventually forced to buy them back and Eritrea took them for free, but not before about 3,770 of the 50,000 sheep died.
Animal Liberation campaigner Ralph Hahnheuser said the sheep could not be harmed by the additive, but it would stay in their system for 21 days.
"The fact is they no longer meet the requirements of countries in the Middle East," Mr Hahnheuser said.
The protest is liable to pose a further threat to Australia's live export trade, which earns the country around Aus$1bn (US$700m) a year.