Lasix: A Comparison of a Horseplayer’s Experience Betting on Horse Racing

Synopsis:   Kelzenberg takes a look at the North American use of race day Lasix as compared to the Australian model of banning all race day medications.

By Anthony Kelzenberg for

Every year or two there is a large debate over the administration of Lasix to North American race horses.  Since I am not a veterinarian or a trainer (and after publishing this document I am sure some trolls will point out ‘what do you know, you aren’t a veterinarian or a trainer’), I will just post my experience as a horse bettor, playing races in America vs. playing the Australian product.

North American Racing (quick summary):

(1)         Expensive bloodstock largely from coming from commercial breeders

(2)         Race distances vary from 4.5 furlongs to a mile and a half (12 furlongs)

(3)         Typical high-end allowance purse (NYRA/So. Cal) is approx. $80,000

(4)         Surfaces are dirt (primarily), grass, and all-weather/artificial

(5)          95% of horses are on Lasix.

Australian Racing (quick summary):

(1)            Expensive bloodstock largely from coming from commercial breeders

(2)            Race distances vary from 4.5 furlongs to two miles (16 furlongs)

(3)            Typical high-end allowance purse (Melbourne/Sydney) is approx. $75,000

(4)            Surfaces are grass and all-weather/artificial

(5)            100% of horses are NOT on Lasix

Note that the racing and economic conditions for USA racing and Australian racing, from a sourcing, distances raced, and surfaces are largely the same.  The two significant differences are North Americans race largely on dirt, while Australians do not (instead, they rotate their race meetings daily to minimize wear and tear on their grass courses), and the North Americans run on Lasix, and the Australians do not.   I am going to use this essay to investigate why the Australians choose not to use Lasix.

The North American perspective:  All horses are potential bleeders, and they all need Lasix to prevent bleeding.

 The Australian reality:  Very few Australian runners bleed.

Bleeding is so rare in Australia that, when it does happen, it is usually reported between live race coverage on Australia’s version of TVG, TVN.  In other words, it is considered “news” when an Australian horse bleeds through the nostrils.  The typical Aussie race meeting (racing day) has 95 to 100 entrants, and, most likely, the number of excessive bleeders per race meeting are only one to three horses, so the amount of bleeders are roughly 1 to 3 percent of runners.  Again, these horses are untreated by vets because race day medication is prohibited in Australia (as it is in most of the leading racing areas), and the incidence of bleeding is very low.  I am ‘not a vet,’ but it might be quite possible that the number of excessive bleeders that show further pulmonary bleeding in North America after getting treated with Lasix probably is higher than 3%.  So what is this Lasix protocol of giving everybody Lasix accomplishing?

The North American perspective:  We produce the fastest horses, and we all know fast horses try hard and can potentially bleed.  So they need Lasix. 

The Australian reality:  The fastest grass sprinters in the world were bred and raced in Australia and our runners can campaign for five to seven years without ever getting Lasix.

Melbourne_Australian racingWhile the Melbourne Cup gets the headlines that go along with a $5 million dollar purse, Australia’s main contribution to the world’s genetic pool is unadulterated speed.  In fact, Australia is internationally known as “The Home of The Sprinter.”  Genetic studies have shown Aussie bloodstock to have a “double copy” of the speed gene that traits back to the Shetlands from Ireland.  In practice champions Choisir, Takeover Target, Scenic Blast and the never defeated and incredibly brilliant Black Caviar were able to have careers that spanned years and were able to win Group 1 after Group 1, in Australia and internationally.  Fans may recall that before Frankel won at 4 years old, Black Caviar was the number one horse in the World Rankings.  All this was accomplished with speed and without Lasix.

What about pace?  Ranking races on their typical half mile split, I would rate the stress on a racehorse in this order (highest stress to lowest stress):

Dirt sprint//Turf sprint//Dirt route//Turf route//Turf marathon

This is where some more data could be helpful because, without a doubt, dirt sprints are more stressful of any race type on the planet.  But they represent roughly 50% of total North American races run.  The experience in Australia shows that racing stress for other types of races can probably be managed without Lasix.

The North American perspective:  Our game is so tough we have to give Lasix to every horse, because the game is so tough.  Races take a lot of a horse too.  Let’s give “Billy Max” 8 weeks off:  look at him, he’s beat! 

The Australian reality:  Because of wet winters and super-hot summers, we give most of our race horses two eight-week breaks during the year to freshen them up.  But when we come to race in the spring and the fall, we are going to plan on running 5 or 6 times over a 10 to 12 week period – every two weeks – with no race day medications.

The Aussie horses are just tougher horses than current North American horses.  It’s that simple.    They are so tough the Aussies have a phrase for when a horse runs on 7 days rest (usually as a stakes prep):  “Backing up.”

The greatest example of Aussie thoroughbred toughness I have seen was the hulk of equine granite named DESERT WAR.  At seven years old, Desert War was in Gai Waterhoue’s barn and really showed the racing world what toughness is:

Here was his racing schedule (note the 4th place finish was at too far a distance for his best, racing every 14 days like clockwork):

Feb 17, 2007 – Group 2 win (1st of 8)

March 3, 2007 – Group 1 (2nd of 10)

March 31, 2007 – Group1 (4th of 14)

April 14, 2007 – Group1 1(1st of 10)

Wouldn’t every trainer or owner want to be involved with a horse like this?  We in the States get excited if the Kentucky Derby winner makes a racecourse appearance once a summer.  At least circumstantially it appears that race day medications are not helping, and compared to Australia they appear to be are hurting our game.

It may be partially genetic, or maybe racing almost exclusively over grass courses has therapeutic benefits, or maybe the application of race day meds like Lasix has an effect on toughness.  Every time Lasix is applied it forces the patient racehorse to urinate.  A LOT.  Generally speaking, mammals do not respond well to dehydration.  And there is also something in the study of medicine called the “kindling effect.”  One time there is a cause applied to a patient, there will also be affect.  When that cause (say Lasix) is applied, over time the effects on the animal’s body can become more and more noticed.

The North American perspective:  Yeah we have small field sizes, but everyone knows the foal crops are decreasing as well. 

The Australian reality:  We have more horses per race than the North Americans do, which leads to better betting opportunities:

As I write this essay (9/26/2014) I looked at the entries per race for Rosehill, Doomben and Sandown-Hillside, the three best Australian tracks on the day.

Track                       Entries        Entries per race

Rosehill                    83                               10.4

Doomben                80                               10.0

Sandown                 112                              14.0

Now contrast the above data with my beloved SARATOGA, which offers the largest purses in North America (taken from the Daily Racing Form website):

For the 401 flat races, there were 3,290 starters, for an average field size of 8.2. Last year, in 411 flat races, there were 3,417 starters, for an average field size of 8.3.

Again, we have not addressed foal crop size, which is the largest factor for field size.  But notice that tonight the three Aussie tracks I will handicap for my Friday night recreation have larger potential field sizes than our most popular track, Saratoga!

Saratoga Racecourse has everything – tradition, history, and the largest purse structure for an extended race meeting anywhere on the planet.  What main component does Saratoga allow that the Australian tracks do not?  Race day medication.  As they say in the social sciences “correlation does not imply causality,” or, in other words, just because a factor is present or not it does not mean that factor is relevant.  But we can definitely make the argument that race day medication probably does not improve field size.

And now a trainer’s perspective (From  Full disclosure – Kiaran McLaughlin has been my favorite trainer for a very long time.

Rather than lean towards genetics to explain the marked drop in starts, New York based trainer Kiaran McLaughlin, one of the 25 signatories on the latest proposal to phase out Lasix, believes horses are simply taking longer to recover from the diuretic effects of Lasix.

“I don’t think like a lot of people do that [banning Lasix] will kill starts per horse – it might do the opposite actually,” said McLaughlin, who in 2011 had rallied in support of Lasix.

I think people would be surprised how few horses actually bleed out the nostrils – it’s really not that many. And even if some of them bleed a little bit, they’re still going to perform and perform well.

For the past two years, McLaughlin has cut considerably the number of two-year-olds he runs on Lasix. “Once we know they bleed,” he says, “we do obviously work them on Lasix, however, and we will sign them up for Lasix on race-day.”

Only a small percentage of those which ran without Lasix bled, he said.

“It’s very interesting. For those two years, we scoped every horse after they ran and most horses after they worked to see where they stood, and I have to say that less than 5% of the horses we ran without Lasix bled at all,” explained McLaughlin, who believes his simplified Lasix program over the past two years proves that trainers mistakenly use Lasix as a wholesale preventative rather than an imperative.

“I think it’s abused in America to the point where 90% of two-year-olds are on it right away, so you don’t know if they’re bleeders or not and you don’t know if they need it or not,” said McLaughlin.

A ban on Lasix would certainly necessitate an adjustment in the way horses are trained and raced, he said.

Maybe they shouldn’t be running so often or as far or in as tough races. And if they are bad bleeders, maybe they need to be stopped on or retired.

This leads to another frequently raised comparison: that climate, training facilities and racing programs make Lasix more necessary in the US than elsewhere.

Unlike the US, where the majority of horses are trained during a short window of time in the morning within the tighter confines of the racetrack, racehorses trained in Europe are, by and large, exercised for longer and in quieter surroundings more conducive to keeping horses that bleed settled and calm.

But McLaughlin counters that the facilities used by the majority of American trainers are no different to some jurisdictions that implement a race-day medication ban.

“I trained in Dubai for ten years and their facilities are very, very similar to America,” he said. “We trained on dirt in the heat and we went left-handed. I just don’t agree with that.”

He said that with a known bleeder, he would try to replicate the diuretic effect of Lasix by limiting the amount of water that horse was given before a race – a practice known as drawing.

“We will obviously pull their water early in the morning, try to draw them a little bit,” he said. “And at the end of the day, there are vitamins out there you can try that are legal.”


(1)            In Australia world class horses successfully compete on aggressive schedules over many years of competition in the spring and the fall without use of Lasix and other race day medications.

(2)            95% to 99% of all race horses do not bleed through the nostrils.

(3)            There is significant anecdotal evidence that Lasix is given to horses to nearly all North American race horses in a preemptive manner for the 1% to 5% that do bleed.

(4)            This overuse of “preemptive Lasix” may introduce destructive effects to the horse over time.

 Did You Miss this Article?

Art Parker’s perspective on Lasix

Share this with your horse racing friends
Handicapping tips from


* indicates required

Email Format

About Editor

Rich Nilsen is a 19-time qualifier to the National Horseplayers Championship (NHC), an event he has cashed in four times. He was the first player to finish in the top 10 of the NHC twice. A former executive with and a member of the NHC Players’ Committee, Rich is a graduate of the University of Louisville Equine Business Program and is founder of, a site devoted to horse racing education and promotion.

Speak Your Mind


This site uses Akismet to reduce spam. Learn how your comment data is processed.

More in Horse Racing Education, Horse Racing Promotion | Marketing, Horse Racing Survival, Thoroughbred Horse Ownership
Trainer Profile: Albert Stall, Jr.

Al Stall, Jr., the 54 year old born in New Orleans, is a part of a well-known Louisiana racing family....