I can't say for sure it was an ill fitting saddle, but many topline issues can arise from an ill fitting saddle. She's been testy getting tacked up, and has been extremely anxious before I mount... She hasn't seemed cold backed or girthy.
Yes, saddle fit is a common problem, but by far not the only one. By the sounds of it, what you describe above IS indeed very 'cold backed' behaviour. Perhaps though you're thinking of it only as collapsing away from you or such & she's not that bad. If she were mine & obviously this unhappy, I wouldn't be riding her. At least until any pain were ruled out. It's possible this 'anxiety' is due to previous remembered pain, not current, or due to previous 'training', but I'd want her to get over that too.
b) it hasn't gotten better with pasture rest, which is the recommendation of many articles .... I simply can't find solid sources for topline wastage.
Re the paddock rest, as with us, depends what's wrong. If you're overworked, you've strained something... or such, then some R&R will likely do wonders. But if you've got something 'out', you have permanent damage, etc, then just resting without addressing the issue can even make matters worse - allow a chronic problem to just progress without treatment.
Re the second bit - finding little info - yeah, unfortunately, like deformed hooves for eg, it's one of those things that are so common as to be thought of as 'normal' & ignored by many. (So good on you for paying attention to it!) Along with the fact that vets, unless specialised, don't generally have a huge amount of knowledge/training about body issues. Just like a GP for humans, a specialist like a physio or a chiro are generally called for for body issues.
Wastage is on both sides. As mentioned, western saddle area. I've seen some horrible Western saddle set ups.
Yeah but just think a Western saddle particularly covers the whole back, so saying the damage is in that area is not really very specific. And doesn't mean that it's necessarily a saddle fit issue. Of course yes, there are many problem saddles, be they western or otherwise that cause probs, but I'd hazard a guess & say that as a kid's horse(presume little kid), she probably wasn't worked long & hard in a badly fitting saddle, so while the saddle could have been *an* issue, it probably wasn't THE issue, or else it probably would have also resolved, or mostly resolved with rest.
She has scars on the corners of her mouth, so I don't doubt it's a bit/past issue, not a saddle issue. As soon as she understands I'm being gentle on her mouth and as soon as I understood she neck reined, things were peachy.
I just think you should be careful about saying 'IT is a bit issue' or such, as just because she has had bit issues too, don't rule out other 'issues'. There may well be multiple issues. And while unyielding hands for eg. can absolutely effect a horse's posture/back also, I'd sus there are back/saddle/whatever other issues too & want them ruled out properly before saying it's just a bit(or such) issue.
about 6 or 7 cups of sweet feed mixed with two scoops MSM, a scoop of glucosomine, 1 scoop SmartMuscle, 1 scoop hoof supplement. She used to get a large scoop of dry beet pulp pellets too, but the vet said that's a no-no
Why the sweets? Is she a 'hard keeper' or such? Obviously not in hard work to require the 'high octane' feed. This sort of feed isn't great for horses anyway. I'm guessing the prob with beet pulp was you were feeding it dry. A lot of people believe it can't be fed dry & causes choke, but that's been found to be false, and fed in small quantities, it's fine. Re supps, look into magnesium - that is one mineral I find very important to supp, for a range of reasons.
Her new saddle fits her like a glove at the moment
That's great, just be aware if it fits her atrophied back now, hope it's quite adjustable & allows for careful padding, or it won't allow room for improvement, won't fit the shape she may change into.