Let me talk a little more about what I mentioned the other day.
Shylah is a fat horse. Often a very fat horse. Yes, there have been plenty of times when I'm lax about riding, but that's certainly not the case lately, and she seems to be ever-expanding. She is fed half the amount that Gwen (a fairly easy keeper herself) eats. Gwen gets zero exercise. Gwen's in pretty good shape, a little round in the belly.
And Shylah doesn't just have a haybelly, she has fat lumps and a cresty neck, and though she's always been a lazy poky horse, but she seems to be getting worse.
A friend suggested I look into Insulin Resistance. Lo and behold it's not uncommon in her breed.
I talked to the vet today, and was surprised by what she said. She told me that most people don't bother getting a horse tested, and she really doesn't recommend the test. The reasons are this:
1) It's a test that requires 12 hours of fasting, but the way that horses digest their food, they would really need 48 hours to truly fast, and that's obviously not too good for the horse, so there isn't a lot of faith in the accuracy of the results of this test.
2) Regardless of whether a horse has IR (apparently more commonly called EMS, Equine Metabolic Syndrome) or is just fat and lazy, the treatment is more or less the same. There is a prescription thyroid medication (no thanks). And there are dietary changes. Only feed grass hay (already do). Restrict access to green pasture (already do). No grain (nope, not since she was a baby). Low starch feeds. There are commercial low starch pellets. $23 per bag, cripes! No thanks.
Soo.... short of getting other vets' opinions, I think I'm pretty much on my own with this. It's hard for me to totally understand, not really totally understanding all about insulin, but I'm going to be experimenting with some feed changes based on some research I've read about and see if I can't get some weight off the girl and pep up the energy a bit.
It's not that I care particularly if she's a bit on the round side, but IR/EMS often leads to laminitis in a chronically overweight horse, and trust me I've had quite enough experience with that. One of three things will happen if a horse get laminitis: they get over and are fine, until it happens again; they don't recover enough to be sound, and are chronically lame and forever a pasture decoration like Gwen; they die like Thunder did.
I don't think I can really "assume" that she has IR/EMS, but I would not be surprised at all, she seems to fit the bill pretty well. So I need to get it under control. I will go to the feed store next week and see what sort of low carb, low sugar, high fiber stuff they have that doesn't cost an arm and a leg. If anyone has experience with an IR/EMS horse please let me know, I'm totally open to any and all suggestions, but would prefer to manage this with diet/exercise and not medication.