I highly recommend a new & extremely good, helpful, comprehensive book on laminitis/founder & rehabbing horses from it; "The Pony That Did Not Die" by Andrew & Nicky Bowe available at Mayfield Barehoof Care Centre Home Page
Also if you haven't yet, Home
& Katy Watts | Safergrass.org
I have a mare who may have cushings disease, EMS, and possibly both but won't know for sure until I have test results.
If you haven't had her tested yet, I personally probably wouldn't, just assume she is IR. When her feet are healthy I might get her tested, but esp if the horse is already suffering, the tests can cause an 'attack'.
In the meantime, it was found recently during a lameness exam that she has very slight rotation
Was she xrayed? If you would like any hoof specific advice about her, posting hoof pics & the xrays would be good. See below for a like for critique pic tips.
I had her back to the vet and she's foundering though vet doesn't believe its acute founder. Vet wants her muzzle on 24/7.
What happened when she 'foundered' suddenly if it wasn't an acute attack?
Grazing muzzles are fantastic.... when they work. As someone said, not designed to be left on 24/7 as they can rub. Sheepskin padding can eliminate that, but need regular checking at least. Some horses somehow(it's always behind your back!) manage to get muzzles off or wreck them, and some horses find them very hard to eat(I've cut bigger holes in the bottom to fix that sometimes) & get depressed. So I'd keep trying, have a play around with it, try part time, etc, but it may not be the best answer for her.
Certainly I'd restrict her access to the hay in the barn. You could put a small holed net over the hay, so they still have free access but can only eat small amounts, not gorge on it. People commonly think of grass hay as much better for a 'lami prone' horse than grass, but it only loses it's sugars while growing & retains them when cut & dried, so depending on type, when it was cut, stage of growth, etc, it could even be richer than the grass. Feeding hay that's tested low NSC is best, or failing that, soaking & draining before feeding to leach out some of the sugars.
suggested that she can be put in the round pen of which the grass has been cut and would soon be a dry lot with her in it and able to graze freely of which the vet confirmed.
If a grazing muzzle doesn't work for her, yes, you'll have to keep her off the grass. Or for the time being & that much grass anyway. I'm guessing the other horse is overweight & could do with a diet too, if it's only them on 5 acres, so may be the ideal situation to look at setting up a track or loop paddock - use tread in posts & electric fencing to create a cheap, movable internal fence around the 5 acres, greatly restricting grazing but motivating more movement too. Move the fence to 'rotate' areas of grazing.
as if many horses cannot be allowed to freely graze on large areas of pasture
Horses are built for little, near constant amounts of poor grade(compared to 'normal' domestic feed) roughage, not unlimited, rich, cattle fattening starchy 'improved' pasture, let alone our improved cereal grains. That is why laminitis is so common. The biggest causes by far of laminitis are insulin resistance, like type 2 diabetes, relates to calorie intake greatly exceeding energy needs/exercise,, and hind gut acidosis, relating to large amounts of starch hitting the hind gut from too rich/large feeds.
I already took Jasmine off grain some time ago (and she never has had alfalfa as she's reactive anyway), though have had to work hard to keep the BO from feeling sorry and giving her some at feed time
Sounds like you have to be strong with BO & perhaps threatening vet bills as Walkin suggested might make an impression.
What is her body condition now(pics)? What is her diet now, including supps? Mixing them with a handful of soy hulls, copra or beet pulp would be an option. I'd look into magnesium if you're not giving it. Google 'Magnesium4Horses' for one good article.
The vet warned me on this trip that another bout could put her into navicular and then just borrowed time after that.
That strikes me as a strange comment and I wouldn't worry about that particularly. Did he say 'borrowed time' because he's one of these that thinks 'navicular syndrome' is incurable? That's not the case either.
I've read a lot about the founder/laminitis but not a lot of info yet I've found about management.
Really? The book & sites above will help you there. IME it's all about management.
I did buy the temp-a-sure strips but found that you super glue them on and there's no instruction about how long to leave them on or when/how to remove them. Not crazy about super glue on my horse's hooves.
Superglue was originally designed for skin/hospital use. I wouldn't worry about a bit on the hoof. Aren't they for monitoring, so you'd leave them on while the horse is likely to have a problem? At any rate, unless she's been standing in hot sun, you should be able to feel that her feet are too hot or OK without a thermometer. Ask the vet for some different spots to feel her pulse too, as the digital pulse is hard to feel when the horse isn't laminitic, so you can get an idea of what 'normal' feels like elsewhere where it's easier. But hopefully you can manage your girl well enough that you won't have to worry about confirmation of 'attack'(which comes with other symptoms anyway) - you'll be able to avoid it.