Do me a favor. Go up into the bar area where trainers are at a place like Woodbine, which races both harness and thoroughbred horses. Ask a question about a first time starter, or any horse really, regarding its bleeding meds.
If you speak to a harness trainer you'll likely hear time and time again:
"He scoped with a little bit of blood, but I'd rather not put him on lasix"
From the thoroughbred trainer you'll likely hear:
"He scoped with a little bit of blood so I put him on lasix"
Almost all horses of both breeds bleed a little bit at least, so why is virtually every thoroughbred on lasix but much fewer harness horses are?
I went through the entries for this weekend's big card at Mohawk. We aren't talking 2 claimers here, but the best in the sport: The 13 race card has purses totalling $2,014,000.
The $166k Breeders Championship for Fillies: 1 of 10 on Lasix, 9 of 10 without
The $159k Breeders Championship for Trotting Colts: 1 of 10 on Lasix, 9 of 10 without
The $750k Maple Leaf Trot: 2 of 10 on Lasix, 8 of 10 without
And on and on.
You can talk about the physical differences, the exertion differences and what have you. But the fact remains that harness trainers choose time and time again to leave their horses off the drug, unless it is really needed. This is likely not altruism: Racing a horse each week with the terrible weight loss with lasix is hard on their systems, and you end up having a tired worn out horse in a hurry, so it cuts down on starts/year, and your horses earnings. But thoroughbred trainers, as a matter of course - with virtually the same amount of blood showing after a work or race - choose to medicate.
A trainer once told me after someone got nabbed with a soda positive that read a huge amount: "To a lot of trainers, if a little bit of something is good, a lot of it must work better"
I think today's modern thoroughbred trainer, with horses racing so few times, wants every inch of racetrack they can get. 'If there's a little bit of blood, we better use lasix, or we're simply not trying.' The owners probably push this as well. If you were the one out of 200 trainers who didn't use lasix and your horse was racing poorly, how long before the horse is moved on you to a raceday med trainer? Likely a week. It pays to join the party.
I think that is why the sport needs policing, and I think that's why you see so many wanting to ban raceday drugs. If the raceday medicine cabinet is open, it will be used in some cases with some people, just because it's there.