If you do need to have your Bs go on thyroid, get it from Omaha Vaccine. It's very cheap at about .02/tab compared to the vet at $1/tablet. That's where I got mine. They will need your vets OK for the prescription. www.omahavaccine.com
Both my german shepherd mix (spayed) and B (neutered) were on soloxine for many years. I got it very reasonably priced from my vet–it wasn't $1/tablet--are you sure it was that expensive? Tyler and Zoey had their thyroids tested, and both are in normal range at this time. My other two were probably middle aged when they had to start thyroid pills. I never used a generic--only soloxine--and it seemed to work fine--I'd get their thyroids tested periodically--but the dose never needed to be adjusted for them.