The horseracing industry is the new Lance Armstrong of the sports world. Before you mix your mint juleps or place that online bet for the Kentucky Derby, think about this: Everyone from the barn hand to the top trainer knows that horses in the racing industry are being doped in a quest to win. And like Armstrong, they deny, deny, deny.

But doping is the worst-kept secret in horseracing: It's pervasive and entrenched. Equine performance-enhancing drugs are being concocted in barns and makeshift laboratories with no regulatory oversight. These backyard alchemists use anything available to see whether it will lead to faster race times: growth hormones, toxic chemicals, even Viagra.

Some trainers inject horses with cobra venom or dermorphin, a powerful opioid derived from the venom secreted by certain South American frogs. Others use a technique called "milkshaking," which involves forcing a large quantity of sodium bicarbonate and sugar into a horse's stomach through a tube. Both procedures are believed to make horses run races faster.

But it's not just illegal drugs that keep unfit horses running - legal painkillers and anti-inflammatory corticosteroids are also being used, and they're killing horses throughout North America. Nearly every horse used in racing is dosed with Lasix, a diuretic that reduces body weight and thereby increases speeds. Lasix also flushes out traces of other medications, which helps avoid detection of these drugs. When the pain of an injury is masked, horses run when they should be resting and recuperating. A California study found that as many as 90 percent of horses who break down and must be destroyed had preexisting injuries.

According to an expose in The New York Times, 24 horses die this way each week at racetracks across America. These horses don't make headlines when their tendons snap or bones shatter. Their battered bodies can earn one last dollar by being unloaded (or, in industry parlance, "vanned off") to rendering plants. Some just end up in landfills like garbage. It bears noting that the greatest number of incidents on a single day - 23 - occurred the same day as last year's Kentucky Derby.

Horses are also dying from what's chillingly called "equine sudden death syndrome," and experts cannot figure out why. In California, at least 26 horses have simply dropped dead since July 2011, including seven trained by three-time Kentucky Derby–winning trainer Bob Baffert. Most of the horses suffered from severe pulmonary edema and pulmonary hemorrhage (acute respiratory distress). Others were found to have suffered from cardiac failure or internal bleeding, including one 3-year-old who had a massive abdominal hemorrhage. PETA has offered a $5,000 reward to anyone who can provide information proving that someone is deliberately killing these horses.

Tracks go to great lengths to shield spectators from breakdowns, quickly shifting into crisis mode when horses hit the turf. Tarps and tents are erected, and announcers don't miss a beat in focusing attention on anything other than the inert body.

Fortunately, the number of spectators at racetracks in America is falling faster than Armstrong's cycling records. The addition of casinos has brought busloads of people in to play the slot machines but has done little to bolster attendance at the track. But one thing that does help to keep this cruel cycle going is when otherwise kind people place bets on the Triple Crown races - the only horse races that most people give even a moment's thought to.

The racing industry needs to implement a zero-tolerance policy on doping. And people who care about horses and don't want them to end up in landfills should turn their back on the racing industry altogether.

Kathy Guillermo is a senior vice president for People for the Ethical Treatment of Animals in Norfolk, Va.