My favorite is Perform N Win and I buy it from The Distance Depot. It is a very nice, mild formula that isn’t too caustic or harsh. It has added dextrose for palatibility and efficient absorption. You can dose 1-3 ounces per hour of sweaty/hot work. When I am planning a long, hot trailer ride I dose before going on the trailer, and after coming off. My experience is that just a single 1 ounce dose doesn’t make a horse crave water, but a couple of doses will so be sure the horse always has access to fresh, clean water in ample supply. If you dose before going on the trailer with more than 1 ounce, I would offer a bucket of water after a couple of hours.
My horses will eat the PnW in soaked beet pulp with no problem. Otherwise I mix it with about 1 tablespoon of water, and 2 tablespoons of Papya puree (Natural Plan Stomach Soother), or you can use applesauce, or Pro-CMC. I use the disposable squeezy condiment bottles that you can buy for $1 at the Dollar Store, or the kitchen supply section of WalMart. Mix everything in the bottle, mix it well, then squeeze it into an electrolyte syringe. (Again, I buy these at The Distance Depot.) You can also reuse an old dewormer or bute tube. Just be sure to wash it out thoroughly first.
You can mix these tubes up ahead of time (this is much cheaper than buying pre-mixed tubes). I store them in the cooler or refrigerator if you have one. When I dose the horse, I squirt it in the back of the mouth and then follow it with a syringe full of water. That just helps wash the salts down the throat and clean the mouth out.
When I’m doing long, hot trailer rides, I be sure to stop only when critically necessary for fuel. I don’t want the horses sitting in the hot trailer, in the sun, not moving unless it is crucial to do so. I make sure my rig is fueled up before loading, then I try to stop just once for fuel. I also pick a place to park in the shade, to minimize heat stress.
I like to use 4 sports medicine boots instead of shipping boots because they are cooler. All the windows wide open of course, and try to travel in the cool of the day if possible. I’ve been known to get on the road at 4 a.m. when I didn’t really need to be on the road until 8 a.m., just because most of the traveling will be over before the sun is high and hot.
If it’s really horribly hot, you can soak the horse in water at your rest stops so they go back on the trailer hot, and the air blowing through the windows will provide more cooling.
You can add a cup of rubbing alcohol to a 5 gallon bucket of water for sponging, which evaporates more quickly and provides even more cooling. Just be SURE the horse doesn’t drink this water.
I’ve seen some people trailer with ice boots on the legs. I haven’t done it, but that might help. They usually only stay cold for a few hours though.
If you have mangers in your trailer, you can provide a wet sloppy mash for them to eat free choice, which will help with hydration.
If this is a 2 week show, I would make sure the horse is well accustomed to eating wet soaked feed, and I would provide soaked hay cubes or pellets, and beet pulp 3x a day. Mine are all well accustomed to drinking their soup, but it can be a real turnoff for a horse who isn’t used to it. Start now and make sure they will eat it. You can mix in applesauce for flavoring, and also their regular grain ration. I would dose at least 2x per day each day that you’re at the show if it’s hot and they’re working.
Provide 2 buckets of water per stall if possible.
Also what I do is to be sure the horse has PLENTY of wet sloppy soaked beet pulp for a couple of days before getting in the trailer. That way their zillion miles of intestines are well loaded with hydrated bulk. A ride vet told me that the feed you give the horse today gets you good gutt sounds tomorrow. So in other words, loading the horse up on wet beet pulp and soaked wet hay today will help the horse tomorrow.
You cannot technically “pre-load” electrolytes - in other words, the body cannot store excess. But, I do start dosing 2 days in advance of going on the trailer, because the horse will be well hydrated with all systems up and running well in advance. I will give 2 doses each day for 2 days before going to an endurance ride, or overnight camping trip where there will be lots of trailer and riding time.
I hope that information helps.
Edited to Add: You could also try Horse Quencher, which is a flavoring for their water bucket, or you can make an oat float by floating a cup full of oats and rice bran on the surface of the water bucket. Sometimes cubes of chopped apples will flavor the water and get them drinking also. Some people use Gatorade powder but I haven’t tried that. If you access to a freezer on the show grounds, you can make frozen apple juice cubes and dump them into the water bucket in the stall.
Ok, what are your fave electrolytes?