Dual Doncaster Mile winner Sacred Falls has died at New Zealand's Waikato Stud after a short illness.

The Waikato Stud veterinary team identified an issue with the stallion's liver a fortnight ago.

Despite receiving world-class treatment at both the stud and at Matamata Veterinary Services equine hospital, the 10-year-old's condition deteriorated overnight and he died early on Sunday.

The son of Waikato Stud's champion sire O'Reilly was in his fifth season of stallion duties after retiring with four Group One wins including his two Doncasters.

Waikato Stud principal Mark Chittick was devastated with the loss of not only a potential world-class stallion but also a horse who held a special place in the hearts of the Chittick family.

"It's been a very tough morning for all the team here as he has been such a cool horse to be involved with," Chittick told NZ Racing Desk.

"He had a wonderful temperament and a really engaging personality and all the staff here just love him.

"He meant a lot to us all, especially as he had played such a big part in our lives during some very tough times."

Chittick was referring to the death of his wife Lisa from leukaemia in May, 2014 and the loss of Sacred Falls' sire O'Reilly.

"When Lisa was sick and receiving treatment, Sacred Falls brought plenty of joy for us when he won the Doncaster Handicap in 2013 and again in 2014," he said.

"When O'Reilly died, Sacred Falls had just arrived at the Stud so it was like the torch had been passed from father to son so he was a very special horse for us all.

"I have nothing but praise for our head vet, Dr Chris Phillips, his team and all the staff at Matamata Vet Services as they did everything in their power to try and save the horse but it just wasn't to be."

Sacred Falls will be buried at Waikato Stud next to O'Reilly, with the Chittick family determining an appropriate tribute to their mate.

Bred and sold by Waikato Stud as a yearling, Sacred Falls won his first six races including the Group One Two Thousand Guineas for trainer Tony Pike and owners Raffles Racing.

Waikato Stud subsequently bought into the colt who added a further three Group One wins in Australia when trained by champion trainer Chris Waller.