
My dog has elbow displasia (UAP), diagnosed at about 5&half months old.
I wouldn't swithc food according to the glucosamine content, just stick to an adult food. Keep his weight down - lean is better than chubby.
I used a liquid glucosamine suppliment at first, it was so brill that pup actually managed without Metacam once the suppliment had worked (was called synflex, think it's been renamed to flexwise now).
I now use a tablet glucosamine, but only as I got given a bulk load that mym mum got a fab deal on!
Glucosamine HCL is more effective (it takes more of the glucosamine sulphate to do the same job as less of the glucosamine HCL). Your vets will probably allready supply glucosamine HCL, but they do tend to be rather expensive when comapred to other places. If using a human suppliment do check the ingredietns are OK for pets soo, some are not and some have contraindications for animals on NSAID (such as metacam).
Cod liver oil suppliments were recomended by the vet, so my dog is also on those.
ETA, Buster has not been opperated on, we've managed the problem with weight control and excersise control.