Champion New Zealand mare Sunline has been put down because of severe laminitis, a disease affecting the hooves.
Part-owner Thayne Green says there was no option but to put down the 14-year-old horse, after having exhausted all avenues to save it.
Mr Green says an expert on the disease came from the United States but could do little.
Sunline was buried on Friday afternoon at Ellerslie racecourse.
Sunline won 32 of 48 starts, collecting almost $14 million in prize money.
