Homeboykris won the first race at the Preakness Stakes in May, but it was the racehorse’s last. He collapsed and died following the post-race Winners Circle presentation while returning to the barn. Such occurrences are common; A racehorse per day died at a track so far in 2016. (Mitch Stringer/USA Today Sports)

On the third Saturday in May, five horses took to starting gates across the United States for their final races. On Preakness day, 9-year-old Homeboykris’s deadly heart attack and 4-year-old Pramedya’s fatally fractured leg caught the attention of the sporting world, which had turned its eyes toward the second jewel of the Triple Crown.

In Charles Town, W.Va., 6-year-old View Tree was competing in the sport’s lowest tier — maiden claiming races in which all entrants are for sale and have never won. She did not finish her ninth race and was euthanized.

Six-year-old San Onofre earned $402,730 before his last start at Santa Anita Park in California. In his 45th start, 11-year-old Brother Sy catastrophically fell over a jump during a steeplechase race in Malvern, Pa.

“Every day we’re killing horses for $2 bets. Why do we still abide this in the 21st century?” activist Patrick Battuello said. “We’re so outraged about the Ringling elephants and the Sea World orcas, and rightfully so, but why not racehorses?”

Each morning, Battuello scans results from America’s tracks in search of catastrophic euphemisms — “vanned off” and “broke down.” Through the first 181 days of 2016, he found 180 , but that number only will grow at the end of the year, when he will again send Freedom of Information Act requests to state racing commissions for lists of horses who have died at racetracks.

Nurse Lynn Hilt, left, and assistant Elizabeth Ortez administer a standing MRI scan at the Equine Medical Center of Ocala, Fla. (Courtesy of Stonestreet Farms)

In 2015, Battuello confirmed 953 .

Natural approach is difficult

The American Jockey Club publishes a database of injuries that lists 484 fatalities in 2015. According to the organization, the fatality rate dropped 14 percent from the year before, from 1.89 per 1,000 starts in 2014 to 1.62 in 2015.

Under the National Uniform Medication Program, 19 of 32 states with thoroughbred racing have adopted uniform regulations for controlled therapeutic substances. Twenty-eight states have standards for test laboratories, and 11 have uniform penalties for trainers with medication violations.

Eighteen states have adopted a policy for third-party administration of Lasix. More than 90 percent of horses in the United States compete on the drug, which prevents bleeding in the lungs but causes dehydration. In the vast majority of international racing, it is banned on race day.

“In the rest of the world, horse racing is more of a sport. In the U.S., it’s got a little bit of a business aspect to it,” said Rick Arthur, the equine medical director at the California Racing Board. “Horse racing needs to become drug-free, and when I talk about drug-free, I’m talking about international standard. I think we need to do that to be able to convince the public that the horse is our primary interest. I think that’s absolutely imperative for horse racing to succeed in a very changing environment.”

The Horse Racing Integrity and Safety Act would grant an independent anti-doping organization the power to regulate American horse racing, which has no national governing body. But the bill, which cites that wagering on thoroughbreds declined 30 percent from 2002 to 2014, has not passed since being introduced in 2013.

“My bill has faced considerable opposition from the racing industry and the organizations that represent it, many of whom have denied for years that the horse racing industry has a problem,” Rep. Joe Pitts (R-Pa.) said. “The many special-interest groups and organizations within the horse-racing industry have helped to divide members of Congress so that not every member is on the same page about what real reform should look like.”

In the absence of such regulation, holistic racehorse owners such as Jim McIngvale, the furniture king of Houston, stand out.

Since 1995, “Mattress Mack” has gone through 45 trainers, thanks largely to a stubborn commitment to drug-free training.

“I kind of went the route of ‘These trainers know more than I do.’ Then the horses kept getting hurt and breaking bones. I knew there had to be a better way,” McIngvale said. “All these trainers — nothing against them, but they want to inject their ankles and their joints with these chemicals and use Lasix. . . . That’s just not the route I want to go.”

McIngvale’s 4-year-old, Runhappy, is trained on a diet of water, hay and oats. At the Eclipse Awards, he tied for second in 2015 horse of the year voting behind Triple Crown winner American Pharoah.

He has not raced since bruising a bone in December.

“The alternative to that is medicating him, and pushing him and pushing him, and pop goes the weasel — it’s all over,” McIngvale said.

At the Fair Hill Training Center in Elkton, Md., trainer Michael Matz bends over to remove rocks from the path leading from his barn to the practice track.

“Rocks hurt to step on. Horses won’t run fast if they’re scared to step,” he explains.

Matz trained the sport of kings’ most famous casualty, Barbaro. Now he trains between 60 and 70 horses at a time and knows the name and personality of each one.

“Some owners want their horses to the races, and [trainers] got to get them there, no matter what. Is that good? No,” Matz said.

“But [owners] look at what the bill is every month, and they say, ‘Jeez, why aren’t we racing? I want to run this horse.’ Sometimes it’s hard saying ‘wait.’ ”

Seeking a pre-race solution

Magnetic resonance imaging has been the standard for analyzing stress-related injuries in humans since the 1980s. There is one machine on property owned by an American racetrack.

“There needs to be a standing MRI in reasonably close proximity to every racetrack,” said John Peloso, a surgeon at the Equine Medical Center of Ocala, Fla., who operates the MRI machine that serves Gulfstream Park.

“These injuries are trying to hide from us, and they’re doing a pretty good job, but now we have a tool that can identify it.”

Doctor Susan Stover estimates that more than 90 percent of catastrophic breakdowns have evidence of a pre-existing injury. On race day, track veterinarians palpate every horse with their hands, watch them jog in search of abnormalities in gait and determine their fitness to race.

Yet warning signs of fractures can often be invisible without advanced diagnostic imagery.

“How unfair it is to ask the regulatory veterinarians to go out and in two minutes figure out if one of these insidious things are going on?” Peloso said.

It costs $900 and takes at least an hour to scan one fetlock, so an MRI is not a viable pre-race scan for every horse.

The challenge for the industry is to van horses to MRI machines to be diagnosed before they race at risk of catastrophic injury.

Sheila Lyons operates around the core belief that ethical standards are resolute, no matter whether the patient has two legs or four.

In 1992, she completed a post-doctoral fellowship in rehabilitation with a focus on sports medicine. At the American College of Veterinary Sports Medicine and Rehabilitation, Lyons teaches how to apply practices of human medicine.

For her, the pathology of fatal fractures is simple. Without rest, horses develop arthritis, which causes bone bruises, which cause microfractures. As horses gallop 40 mph, each leg takes a turn to hold the 1,200-pound athlete in the air.

“People always say ‘the horse just took a bad step’ and that’s just not true,” Lyons said. “Any horse that dies is an absolute failure of the veterinary system that was looking after the athlete.

“These are not single-step failures. These fractures occur over a long period of time.”

CT imaging equipment company CurveBeam’s pedCAT scanner produces high-resolution 3-D images of the human foot. In 2013, Lyons approached CurveBeam about adapting the technology for horses. In June, it completed a prototype design that can scan the lower limb of a standing racehorse in roughly a minute.

The scanner would cost an estimated $300,000 and produces images capable of revealing fatal warning signs.

Lyons is applying for grants for funding to start implementing the technology as a pre-race screening device to stop the carnage.

“I am absolutely certain that we will reduce racing fatalities to absolutely nothing if we can develop this technology and scan every racehorse,” Lyons said.