Hi, while you've probably found an affordable source of glucosamine for your collie by now, I'll just post my bit here in case folks, also considering similar dietary supplements that might help with canine arthritis, want to compare.
First of all, I heard that glucosamine is supposed to work better when combined with chondroitin, so I've bought them together:
GNC brand - google URL (good range in larger Mannings stores in HK)
Glucosamine (250mg) & Chondroitin (200mg)
[both sulphate forms] 90 softgel capsules
Normal price HK$299.90; current sale $285.90
If just the gluco, then:
Glucosamine [sulphate] (550mg)
30 softgel caps
Normal price HK$88.90; current sale $79.90
Glucosamine [sulphate], PLUS Herbs & Nutrients
[Devil's Claw, Yucca (anti-inflam.), selenium, magnesium, etc]
60 softgel caps
Normal price HK$229.90; current sale $199.90
I've got GNC member card, so get 20% discount off supplements every month (on only the first few days tho). Plus, I get an extra 5% off as well coz of Apita credit card. (That's why I prefer getting my fish oils, gluco+chond, etc, from that dept store with a mini-GNC counter, too!)
Several PET shops here also sell gluco etc, but, personally, I think that, perhaps, "human grade" is an insy bit better... (dunno). Anyways, I've checked, asked around: generally, prices aren't that much different, UNLESS, of course, you order online in bulk from "recognised brands" with mail-order service.
BTW, I'm sure - from your own research - you've gathered that the acceptable daily dosage depends on the weight of your dog. Don't follow usual bottle recommendations. (Consult vet if in any way unsure.)
Wish you & ya furry friend the best