Maggie the Kelpie, an Australian dog that was thought to be the oldest in the world, has died at the age of 30 leaving her owner devastated.

She was the best friend of Victorian dairy farmer Brian McLaren who confirmed the news, saying that Maggie passed away peacefully on Sunday night.

The beloved dog was still wandering around the dairy in Woolsthorpe, west of Melbourne, and growling at cats in the weeks before her death.

But Mr McLaren said that the Kelpie, who was more than 200 in dog years, went downhill in her last two days.

Maggie the Kelpie, an Australian dog that was thought to be the oldest in the world, has died at the age of 30 leaving her owner devastated

Maggie the Kelpie, an Australian dog that was thought to be the oldest in the world, has died at the age of 30 leaving her owner Brian McLaren (pictured) devastated

'She was 30 years old, she was still going along nicely last week, she was walking from the dairy to the office and growling at the cats and all that sort of thing,' Mr McLaren told the Weekly Times.

'She just went downhill in two days and I said yesterday morning when I went home for lunch ... 'She hasn't got long now'.

'I'm sad, but I'm pleased she went the way she went.'

Maggie has already been buried beside the McLaren's other dog in a marked grave under a pine tree.

Mr McLaren said that the Kelpie, who was approaching her third century in human years, went downhill in her last two days

The beloved dog was still wandering around the dairy in Woolsthorpe, west of Melbourne, and growling at cats in the weeks before her death

'We were great mates, it is a bit sad,' he said.

Maggie was a contender for the oldest dog in the world, but Mr McLaren lost the original paperwork for the dog, meaning that her age could not be independently verified.

The Western District owner previously spoke about the fact that his youngest son, Liam, was four years old when they bought Kelpie Maggie as a young pup. Liam is now 34.

Officially, the title of the oldest dog in the world still belongs to Bluey, an Australian cattle-dog from Rochester in Victoria, which reached 29 years and five months.