Performance-Enhancing Effects Of Lasix
By Joe Goraje
The Kentucky Derby is just a few days away. In a typical year the focus leading up to the race would be on analyzing contenders, making selections (plural, because of all those exotic wagers), and planning your Derby festivities.
There is nothing typical about 2019.
The public outrage regarding the 23 equine fatalities during the current Santa Anita race meet has led The Stronach Group to propose several industry reforms, including a ban on the race day use of furosemide (Lasix). On April 18, 2019, the reform movement extended to nearly every corner of the country with the announcement of a coalition of nearly every major racetrack, including Churchill Downs, to enact a partial ban on the race day use of Lasix.
Racing’s hot button issue has now officially come to a boil.
The concern on both sides of this issue is immense. Now, more than ever, is a good time to let a few facts speak for themselves regarding the performance-enhancing effects of Lasix.
In this column I’ll revisit the most definitive study undertaken on determining the effects of race day Lasix and provide, for its first public viewing, recent relevant data from the past three years.
The definitive study
The peer-reviewed study was published in the Sept. 1, 1999, issue of the Journal of the American Veterinary Medical Association. Its title: Effects of furosemide on performance of Thoroughbreds racing in the United States and Canada.
Th authors analyzed 22,589 race records provided by the Daily Racing Form. These records were of horses that finished a race on a dirt surface in the United States and Canada between June 28 and July 13, 1997, in jurisdictions that allowed the use of furosemide. Of that total, 16,761 (74.2%) had been administered Lasix.
The authors concluded that:
“Horses that received furosemide raced faster, earned more money, and were more likely to win or finish in the top 3 positions than horses that did not. The magnitude of the effect of furosemide on estimated 6-furlong race times varied with sex with the greatest effect in males.”
When comparing horses of the same sex in six-furlong races, the authors determined the difference between racing with Lasix versus without was 3 to 5.5 lengths.
The authors attempted to sort out possible explanations for the superior performance of horses on Lasix. The discussion on weight loss is worth revisiting.
“Another explanation for the performance-enhancing effect of furosemide is the acute reduction in body weight that occurs after furosemide administration. Intravenous administration of furosemide has been shown to induce a 2 to 4% reduction in body weight within 4 hours. Because work is a product of mass, velocity and distance, and given the acknowledged importance of weight carriage when handicapping Thoroughbred horses, it would be expected that loss of this amount of weight would have a beneficial effect on the athletic ability of furosemide-treated horses. This contention is supported by reports that the furosemide-induced reduction in body weight increases the maximal rate of oxygen consumption, reduces accumulated oxygen deficit and apparent rate of lactate production, and decreases the rate of carbon dioxide production of horses during intense exercise.”
Fast forward 20 years
This past winter I spent a considerable amount of time reviewing data regarding horses that competed without race-day Lasix. Much of that information was published initially in a Paulick Report piece titled, Winning Without Lasix In 2018: McPeek, Rivelli Top All U.S. Trainers.
In reviewing this data, I came across information that very closely tracks the conclusions reached in the 1999 study regarding the performance-enhancing effect of Lasix. The table below reports the placing of all horses competing in the United States without Lasix in each of the past three years.
What caught my attention was the discrepancy within this subset of horses racing without Lasix. In this group, 2,601 horses finished 1st while 4,734 horses finished 6th. If Lasix did not enhance performance, the number of these horses placing 1st and 6th would be roughly equal. That’s because almost all races have at least six horses. To illustrate this point, take for example a set of 1,000 races each with six-horse fields. There would be 1,000 winners, 1,000 2nd place finishers and so on, including 1,000 6th place finishers. Isolating horses that did not receive race-day Lasix we see that they significantly under-performed.
In other words, an untreated horse has an equal opportunity to finish 1st, 2nd, 3rd, 4th, 5th, and 6th unless, of course, racing without Lasix puts it at a disadvantage.
Using the composite 2016-2018 data, horses racing without Lasix were 82% more likely to place 6th than to win.
Also of note is the increase in use of race-day Lasix in the past 20 years. Lasix was administered to 74.2% of starters in the 1997 study compared to 96.4% in 2018, which is, of course, what you would expect to see with the widespread availability of a performance-enhancing drug.
A key question is why is there such a large difference between the number of horses that finished 6th compared to those that won the race?
The answer is in the 1999 study.
It’s 3 to 5.5 lengths.
Former Indiana Horse Racing Commission executive director Joe Gorajec is a consultant whose clients include Horse Racing Reform, an industry initiative led by The Jockey Club and Thoroughbred Owners and Breeders Association.
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