I really would be a little more cautious with all that you're putting in this mix. I'm sure we all supplement our oldies with Ensure, but when you start mixing and matching supplements you can do more harm than good if you don't pay attention.
As per RatGuide, the recommended dosages for Glucosamine/Chondroitin is 1/6 to 1/4 tablet containing 250mg/200mg or 40mg/kg a day. The Elations drink contains 1500mg of Glucosamine and 1200mg of Chondroitin. At those ranges, a 600g rat shouldn't be getting more than .02 - .03cc once a day. There's also a concern for over supplementing. Both Boost and the Elations drink contain a good amount of Calcium. You can overdose on this, and it can cause major organ dysfunction. Overdosing on Calcium can cause renal [kidney] failure, especially in older patients.
Also, Ibuprofen is a medication to be used to
treat pain, not to treat the idea of pain. You can cause a very serious resistance to the analgesic and anti inflammatory effects, so that when they really do need it the proper dosage won't help them any. It can cause excess bleeding, stomach problems, can cause death in renal patients, and can also mask the symptoms of an infection. Even with the lower concentration of Children's Ibuprofen, a 600gram rat would still only be getting .30cc per dose for pain relief. A single teaspoon is 5mls, so your mix contains well over the recommended amounts.
I would strongly suggest you rethink this mix and giving it to your rats. If you wish to supplement, then by all means you should. Just do it with the proper information so you can really help your rats.
Article on Glucosamine/Chondroiton supplements
Article on Ibuprofen