I was unaware Taurine had to do with musculature, but I’m definitely no expert on dog nutrition. I do know that high protein diets are the best for getting a dog back up to a healthy weight and building muscle. As far as maintaining them, though, will she have a normal level of activity? You don’t really need high protein or anything like that just to maintain – you just need a normal rounded diet and plenty of exercise to keep her in shape. Humane societies don’t typically receive much aid from THE Humane Society, so they can’t afford top shelf dog food – they take what they can get in donations. They probably only sent you with it so you could switch her to a new food slowly instead of all at once, which would give her tummy upset.
Unless she is underweight or in poor condition, I wouldn’t feed high protein. She’s just going to pack it on in weight if she isn’t working harder to burn it.