i gave each of my Tosas some ester C and joint support up until a year. i use human supplements, and found some C powder, and capsules with Glucosamine, Chondroitin, and MSM. the amount of C i added may have been about 200mg/day and the joint support, half adult dose until 6 months, then full dose after. maybe large and giant breeds sometimes don't produce quite enough C to keep up with the manufacture and maintenance of collagen and all that goes into joints?