My oldest brother introduced me to the phrase "gotta piss like a racehorse" when I was young. Given my tiny bladder and significant drinking appetites, I've since found ample opportunity to use it. Never thought about what it meant.
Then a few months ago- during the Kentucky Derby, probably? There was an NPR piece about racehorse drug culture. Yeah, it's a thing. It swings two ways:
A) Racehorses are subject to all the competitive pressures that your average Tour De France cyclist experiences. Correspondingly, jockeys will try to "dope" their horses if they can get away with it. And given that a horse is much less likely to object, they've been known in the past to get pumped full of all sorts of crazy shit.
2) The nature of the race puts all sorts of weird pressures on a horse's system, which is already apparently sort of wonky. Racehorses are particularly vulnerable to something called "exercise-induced pulmonary hemorrhage," wherein capillaries in the airway burst, expelling blood all over the fucking place including down into their lungs and out their noses.
So jockeys end up pumping all sorts of other fun drugs into their horses to curb race-related maladies, which can be potentially fatal. Like, mid-race-drop-dead fatal.
To control EIPH, they've been known to use Furosemide, which draws fluid away from the lungs. Here's a breakdown that does it justice in a way I can't:
Furosemide is a diuretic. Takes all that water and deposits it into the horse's bladder for disposal. Side note: it's also postulated that Furosemide is in itself a performance-enhancing drug, as it allows the horse to expel all unnecessary fluid and presumably shed a few pounds right before the race. Don't know the specific science behind that claim, or if it holds up.
So! A) horses are known for their prolific bladders in totally normal conditions and B) Furosemide is a strong diuretic. It all adds up to a whole lot of piss, most specifically in regards to racehorses.
I'm proud of this assessment because the news piece never directly mentioned the "piss like a racehorse" thing. Just mentioned in passing that Furosemide was a diuretic and light bulbs went off in my head.
I'm also proud that I can retain as much information as I did from a half-year old news piece. Don't take that for granted these days.