The authorities in Australia probing the deaths of 174 sheep on board a Singapore Airlines Cargo plane from Perth to Singapore said it is "rare" for animals to die in flight.
The country's Department of Agriculture, in an e-mail reply to The Straits Times yesterday, said Australia has exported more than 31,000 sheep by air since January and only three did not survive the journey.
The Oct 2 flight was carrying 2,200 sheep.
Exporters moving sheep and goats by air are required by law to inform the Australian authority if at least 2 per cent of the consignment or three animals, whichever is greater, do not survive the flight.
The department, which said that the deaths were unacceptable, is working with Singapore's Agri-Food and Veterinary Authority (AVA) to investigate the deaths.
The AVA has inspected the sheep and sent several carcasses for post-mortem. It said that heat stress was the likely cause of death.
SIA Cargo, which carries live animals on a regular basis, is cooperating with the authorities.
An SIA Cargo spokesman said the animals were handled strictly according to livestock guidelines provided by the International Air Transport Association (Iata).
In this case, the sheep were accompanied by attendants, who were hired by the exporter.
The spokesman added that there are "inherent risks with the transport of any animal".
"On the rare occasion, some animals may not survive," he said. He did not say whether there had been deaths on previous flights.
An Iata spokesman said animals must be flown in a "safe, humane" way, with a 474-page book detailing guidelines for airlines and shippers.
There are different rules for different types of animals.
The Iata spokesman said: "Most species do not need to be fed under normal conditions but at a specific time before departure. Depending on the species, attendants need to check on the animals."
The sheep that died were being flown here for the annual Islamic sacrificial ritual of Korban, in which livestock are slaughtered and the meat is distributed to worshippers and the needy.
If investigations show the rules were not complied with during the transportation of the animals, the Australian Department of Agriculture can take regulatory action against the exporter.
Its spokesman said: "The exporter and the airline both have responsibility for the safe carriage of the livestock."