A farmer was astonished when an ageing cow gave birth to a quad of calves - at odds of 11 million to one.

The three baby males bulls and a heifer are all doing well under the care of farmer Brian Omand, 62, and his son Liam, 19.

The calves' mother, a 12-year-old Aberdeen-Angus cross, went into labour last Saturday at Stembister Farm, Toab, Orkney.

Brian believes the statistical likelihood of quads being born naturally was 700,000 to one.

But the chances of all four calves being born alive was an astounding 11 million to one.

Brian said: "There is an 11 million to one chance of them being born alive, and a 700,000 to one chance of them being born.

"They are doing very well, they are running about.

"We are having to supplement them with artificial milk, as with four calves the mother's milk just disappears.

"Everything was natural. I had no idea she was expecting so many."

The multiple births did not show up on pregnancy scans, so Brian was surprised when he put his hand on the cow's stomach and felt a bundle of legs.

Brian added: "There was a whole pile of legs.

"It was a few minutes before I sussed out what belonged to what.

"I got the first out, then the second followed, then I got the next one out, and the last one.

"It took 20 minutes.

"We have had a set of twins before, and I have heard of triplets being born, but not quads.

"They were smaller than usual but fully formed.

"Their mum is doing really well - she's quite an old girl."

Brian says it is uncommon to have four calves, but to have them living is even more rare.

The fact that all four are thriving has surprised him.

He added: "Normally the strongest will survive, but the weakest won't.

"I've never seen anything like it."