My vet recommends Chondrocyte. It is not carried at regular feed stores, but you can order it online. He says Cosequin and Chondrocyte are the only glucosomine supplements that have been tested and shown to have what they say they have. Chondrocyte is much less expensive.
He also says that after the loading dose you can feed it as little as once a week or as often as daily, depending on the horse. Once the supplement is in the joints, you only have to give enough to replace what the is being used up. The only way to figure out how often you have to feed it is trial and error.
Cosequin is pretty much the gold standard in joint supplements for efficacy and quality and guaranteed quantity of ingredients. It's been empirically proven to slow cartilage degeneration. I think it makes a difference for some horses, but not others. Every vet I've worked for/worked with/met has recommended it for athletes and anything with potential arthritic changes (pretty much all horses).
I definitely notice a difference in one of mine when she goes off of it (10 yo TB/WB mare).
I used it for a while, but didn't notice much of a difference. :/ I could tell when he was on Platinum Performance CJ, though. I'm about to try Cavalor ArtiMatrix and see how it goes. I have heard many great things about it, but time will tell.
Another note - it works to prevent/slow down degeneration, so although you may not see your horse get better, it prevents them from getting worse. It's kind of like taking calcium to prevent osteoporosis - you don't really get better from taking the calcium, but it prevents your bones from weakening.
I would surmise that one advantage of the Cosequin oral supp is that the horse gets it daily. Consist level. The injectibles are not too long lasting.
Plus, while I am comfortable giving IM injections, IA is whole 'nother thing.
And injections directly into the joint DO carry some risks of infection and complications.
I've done each and all of the above, and to me, oral supps seems easier and more consistent unless the horse has some specific very problematic joint issue that's still uncomfortable after a few months of being on Cosequin.
I know the original formulation of Cosequin had quite a bit of research behind it and has been proven to be effective. I'm not sure about the newer formulations (Cosequin, ASU etc.) I've had my mare on it since I got her. My dogs &
I also take it. I know I can feel a difference when I run out and miss a week or two and my 13 year old lab can still comfortably jog a 5K so I definitely think its worth the $.
My other suggestion, outside of supplements, would be to talk to your farrier. There may be some things like padding or gel inserts, that can help provide additional protection from wear and tear. There are so many things they do to extend an older horse's jumping career that seem like they would help a younger horse if you thoguht it worth the investment.
I use the Cosequin powder (on horses & dogs). By original I meant "Cosequin" as opposed to Cosequin with MSM or Cosequin ASU. Those may be great but I don't have enough information to comment on them. I didn't do loading doses on my guys since it was preventative, not addressing a current condition. I definitely used the loading dose on me
Since you're obviously very concerned about keeping your horse happy/healthy for the long run, you might also look at your post work routine. May be worth researching long term benefit of Back on Track wraps or ice boots after jumping. Also, I think the biggest thing is weight management. I wouldn't want my jumper overly skinny but I think keeping her lighter than the typical hunter is better for her joints.