Campaigners argue the live sheep trade is cruel

More than 53,000 animals were loaded on to a ship in Portland in Victoria state amid tight security.

Reports said the sheep were bound for the Persian Gulf, but did not say which country.

The export of animals to Middle Eastern countries stopped after campaigners fed pork to sheep in November.

A sheep shipment had to be cancelled because, under Australia's livestock rules, sheep that have been fed animal products are no longer judged fit for human consumption.

"There was never really any doubt that export would resume," said Philip King, the owner of a feedlot where the sheep were prepared for the trip.

"Buyers in the Gulf have faith in our operations and made that clear during the last incident," he said.

Australia ships live animals to Muslim countries so that they can be killed in the traditional way to provide halal meat.

Animal rights activists argue that the trade in live sheep is cruel because of the conditions of transportation.

The issue was highlighted last year when Saudi Arabia refused a consignment of 55,000 animals saying that more than 5% of them suffered from scabby mouth disease.