Roberto's great sire son Dynaformer, sire of Melbourne Cup winner Americain, has died at Three Chimmeys Farm in Kentucky.

The death of the 27-year-old stallion, who had been pensioned after suffering an aortic valve rupture on April 14, was reported on Sunday.

"Dynaformer impacted the industry in a way that few ever have or will," said Three Chimneys president Case Clay.

"More than that, though, he was an awe-inspiring horse to be around."

Apart froim Americain, Dynaformer sired GI Kentucky Derby winner Barbaro, multi-millionaire Perfect Drift and European champions Rainbow View and Lucarno.

From 21 crops to race, Dynaformer's progeny have earned over $105 million and he is the sire of 61 graded stakes winners, 25 G1 winners and 18 millionaires.

He is also the broodmare sire of 78 stakes winners.

"Dynaformer's tough spirit will continue to influence our breed for many years to come," said Three Chimneys owner Robert Clay.

"He reminds us that looks aren't everything, and that the will to win is that intangible ingredient we are all striving to find."

Three Chimneys stallion manager Sandy Hatfield added, "He commanded respect and total attention at all times. He had earned every bit of his reputation as being one of the toughest stallions in the industry, but when it came to his job in the breeding shed, he was a total professional.

"In my opinion, our industry has lost one of the greatest sires it will ever see."

Dynaformer will be buried in the Three Chimneys stallion cemetery.