The roar of hooves thundering down the stretch of a horse race is one of the quintessential Kentucky experiences. The hypnotic, huge strides of the horses move with a grace that draws people to the grandstands, where they cheer for a horse by its number or its name (as in Seabiscuit, whose story captivated millions). But horse racing is also a brutal industry that is structured around cruelty, and repeated attempts at reform have failed to change things. The sport kills two jockeys and 60 people paralyzed each year; meanwhile, the horses suffer and die in ways that most Americans would find hard to believe.

Running fast comes naturally to thoroughbreds, but winning a race is a human construct. In the wild, horses—who are prey animals—prefer to run as a group and keep each other safe. But to win a race, they must outrun their opponents, and that requires the horses to be pushed onward by humans, using a whip.

When horses are whipped, their lower legs take a terrible pounding that strains ligaments and tendons. They may be injured to the point of crippling themselves for weeks or even months, and they are prone to kick themselves and each other.

For this reason, a horse’s lower leg must be protected. Mongolian Groom wore blue bandages on his lower legs and was wearing a shadow roll to prevent him from getting startled by the shadows on the track, which can cause injuries. He was also wearing a hat to shield his eyes from the sun.

Besides the protective gear, many race horses wear padded girths, which are tightened and loosened to distribute weight evenly across the horse’s body. This reduces pressure on the feet and helps avoid sores. Some are also given antibiotics to fight infections, and some are treated with a steroid called sulfadine that prevents bacterial skin infections.

Most flat races are run over distances of 440 yards to four miles (6.4 km). Short races, known as sprints, require rapid acceleration, while long-distance races are considered a test of stamina. In addition to sprinting, some horses are trained to jump over obstacles—a form of racing known as hurdling or steeplechasing—and to run longer distances.

In the past, it was common for a single large investor to own a racehorse, but today, racehorses are often owned by syndicates, in which dozens of small investors share ownership. These syndicates usually divvy up the shares into “microshares” that cost only a few hundred dollars a year. This trend has democratized the sport and strengthened its bottom line, but it also means that each horse is less likely to be a big money winner.

All of the horses in the race that day had been injected with Lasix, a diuretic marked on the racing form by a boldface “L.” It is given to all thoroughbreds to protect them from pulmonary bleeding caused by hard running. This can happen at any time, and is sometimes fatal.