Almost 50 prized stud cattle flown to Kazakhstan by a WA exporter are thought to have suffocated late last month because of a suspected fault in the aircraft's air-conditioning system.
The Federal Department of Agriculture is investigating the death of 49 cows flown to the central Asian country late last month by Perth-based company Livestock Shipping Services.
The animals were part of a consignment of 321 cows flown from Victoria aboard a 747 cargo jet owned by New York freighter Atlas Air.
The cows were found dead when the aircraft was unloaded in Kazakhstan.
Local reports said the animals were thought to have suffocated after a possible failure in the aircraft's air-circulation systems and a build-up of gases from faeces.
A longer than expected refuelling stopover may have exacerbated the situation.
LSS general manager Garry Robinson said the company had reported the incident and was helping with the investigation.
"It's extremely disappointing and we are deeply worried about it," he said.
"It's certainly an uncommon thing in the world of air freight."
Mr Robinson said the entire shipment of category one stud heifers was valued at about $1 million.
It was the fifth such consignment the company had sent to Kazakhstan.
The Department of Agriculture said the company was obliged to report the incident because the mortality rate of the shipment was more than 0.5 per cent.
"The department is investigating the reasons for the mortalities, working with the exporter," a spokesman said.
A spokeswoman for advocacy group Animals Australia urged the investigation be completed quickly. "These animals would have suffered terribly in the lead-up to their deaths," she said.As breeder cattle, the animals are not subject to the Government's anti-cruelty regime.