Sunline, arguably the best New Zealand-trained galloper since World War 2, has been laid to rest at Ellerslie racecourse after losing her battle with a hoof disease.

The 13-year-old mare who captured the racing public's imagination in Australia and New Zealand was put down this morning after vets decided it would be inhumane to let her live with her laminitis.

Stephen McKee, who trained the mare along with his father Trevor while she was racing and became her co-owner soon after Sunline retired, said she had been buried today at Ellerslie racecourse, headquarters of the Auckland Racing Club.

"We asked to put her at Ellerslie where people could actually see her rather than just on the farm," he told NZPA.

"Luckily Ellerslie were very receptive to our wishes and they moved pretty quickly.

"She's got a great resting spot there actually, not far out from the tie-up stalls, going back towards the gardens. There's a little walkway down where we'll put up a headstone."

A world expert on laminitis, Ric Redden from the United States, who has 35 years experience dealing with the equine illness, visited Sunline and the McKee family, who own the mare, on Monday.

Redden noticed she had lost all quality of life due to the disease and they decided there was no option other than to have her humanely put down.

McKee said she had been suffering from laminitis for the last 12 months.

"She's had times where she's looked really good but it was just a case of losing all blood supply to both her front feet in recent weeks.

"In the last few weeks she'd really started to look like she was suffering."

Sunline was the star of Australasian racing through most of her racing career between 1998 and 2002, winning 32 of her 48 starts.

At the time she retired she had earned an official Australasian record of $14.1 million, an amount only surpassed since by another great mare, the three-time Melbourne Cup winner Makybe Diva.

Sunline was bred by Susan Archer and Michael Martin. They sent their mare Songline, who traced in her pedigree to a sister to the legendary Australasian champion Phar Lap, to the imported sire Desert Sun, and Sunline was the result.

Sunline was born at Pleasanton Farm in Cambridge and reared there by highly respected horsewoman Ngaire Fraser.

She was leased by Archer and Martin to Aucklanders Trevor McKee, Thayne Green and Helen Lusty, who exercised a $40,000 right of purchase in the spring of 1998.

It was about the time she won her first group one race, the 1998 Flight Stakes (1600m) for three-year-old fillies in Randwick, Sydney.

She later won another 12 group one races. The most important wins were dual victories in the Doncaster Handicap and the Cox Plate, her second Cox Plate victory by a record seven lengths.

Sunline also tasted international success, winning the Hong Kong International Mile (1600m) from local hero Fairy King Prawn. She also ran third in the 2001 Dubai Duty Free.

"As far as the wins go, I think they're all great because she always raced against the best," Stephen McKee said.

"There's a few particular ones that stand out but really at the level she raced at we were more than happy with what she did all the time."

Among her achievements were an unprecedented four New Zealand Horse of the Year titles, and three Australian Horse of the Year titles.

Sunline's regular rider was expat New Zealander Greg Childs, who was on board for 11 of her 13 group one victories.

"She lifted my profile ten-fold and my bank balance the same amount," Childs said when he retired earlier this year.

"She got better as she got older. She was masculine looking and she showed that on the racetrack too by demolishing the opposition."

Sunline had four foals as a broodmare. Two have raced, and both have won once - her first Rock of Gibraltar filly Sunstrike, now four, and a Zabeel colt, Sun Ruler.

The latter, now three, is the only one of Sunline's progeny to be sold at auction, fetching $2 million to the bid of south Auckland real estate agent Don Ha.

She also has a two-year-old filly by Rock of Gibraltar and a yearling filly by Hussonet.

All the fillies are owned by Stephen and Trevor McKee, while they have also trained Sun Ruler.