SmartFlex Ultra is the better joint supplement. It delivers 10,000 mg of glucosamine and 10,000 mg of MSM per scoop — both at full therapeutic threshold. Cosequin ASU delivers 7,200 mg and 5,000 mg. That’s 72% and 50%. On the thing that matters most in a joint supplement — how much active ingredient actually reaches your horse — SmartFlex Ultra wins and it’s not particularly close.
Cosequin ASU has one real advantage: it’s the only product in our database with a full dose of ASU, and its manufacturer (Nutramax) runs the tightest publicly documented quality program we’ve scored. If that matters to you, it’s worth the trade-off. For most horses, it doesn’t outweigh the dose gap.
The Scores
| SmartFlex Ultra | Cosequin ASU | |
|---|---|---|
| Overall | 6.8 | 6.5 |
| Label Transparency | 13 / 15 | 12 / 15 |
| Ingredient Form | 17 / 20 | 15 / 20 |
| Dosing Adequacy | 17 / 20 | 12 / 20 |
| Formula Design | 9 / 15 | 10 / 15 |
| Quality Assurance | 1 / 15 | 6 / 15 |
| Value | 11 / 15 | 10 / 15 |
| Badge | Recommended | Recommended |
| Cost/day | $1.84 | $1.73 |
Label Transparency, Formula Design, and Value are close enough to be a wash. The story is in three dimensions: Dosing Adequacy, Quality Assurance, and Ingredient Form.
10,000 mg vs 7,200 mg — That Gap Is Real
SmartFlex Ultra hits 17/20 on Dosing Adequacy. Cosequin ASU hits 12/20. Five points apart on a 20-point scale. That’s the biggest single-dimension gap in this comparison and it drives the overall result.
Here’s what that looks like in practice. Your horse weighs 500 kg, works four days a week, and you want maintenance-level joint support. The research literature points to 10,000 mg/day of glucosamine as the therapeutic threshold. SmartFlex Ultra delivers exactly that. Cosequin ASU delivers 7,200 mg — about three-quarters of the way there. Is 72% enough? Maybe. Plenty of horses do fine on it. But you’re paying nearly the same daily cost ($1.73 vs $1.84) for 28% less of the primary active. That math doesn’t work in Cosequin’s favor.
MSM tells the same story but worse. SmartFlex Ultra: 10,000 mg, full threshold. Cosequin ASU: 5,000 mg, half dose. If you believe MSM matters for joint support — and the research increasingly says it does — half-dosing it is a real compromise.
One place Cosequin ASU holds its own: chondroitin sulfate at 1,200 mg versus SmartFlex Ultra’s 1,000 mg. Neither product comes close to the 2,500 mg threshold, but Cosequin is marginally less underdosed. And where SmartFlex Ultra includes 100 mg of hyaluronic acid (right at threshold), Cosequin ASU skips HA entirely in favor of ASU at 1,050 mg. That’s a deliberate formula choice, not an oversight — and it’s the subject of the next section.
Cosequin’s Ace: ASU and Quality Control
Cosequin ASU does two things that SmartFlex Ultra doesn’t do at all.
First, ASU. Avocado/soybean unsaponifiables at 1,050 mg — a full therapeutic dose. ASU works differently from glucosamine or MSM. Rather than providing building blocks for cartilage, it appears to inhibit the enzymes that break cartilage down. That’s a complementary mechanism, not a redundant one. No other product in our database delivers ASU at this level. If your vet has specifically recommended ASU for cartilage protection, this is your only scored option.
Second, quality documentation. Cosequin ASU scores 6/15 on Quality Assurance versus SmartFlex Ultra’s 1/15. That’s the widest gap in the other direction. Nutramax uses trademarked ingredient specs — FCHG49 for glucosamine, TRH122 for chondroitin, NMX1000 for MSM — which are essentially batch-level quality fingerprints. They describe 80+ quality checks and state they test for contaminants. SmartPak’s product page has no certification, no COA, no described QC program. SmartPak is a respected brand. But “respected brand” isn’t a verifiable quality claim. Nutramax puts receipts on the table. SmartPak doesn’t.
Does this change the recommendation? For most recreational horse owners, probably not. For someone feeding a competition horse where a contamination flag ends your season, Cosequin’s documentation provides peace of mind that SmartFlex Ultra currently can’t match.
What’s in Each Scoop
| Ingredient | SmartFlex Ultra | Cosequin ASU | Threshold |
|---|---|---|---|
| Glucosamine HCl | 10,000 mg (shellfish) | 7,200 mg | 10,000 mg |
| MSM | 10,000 mg | 5,000 mg | 10,000 mg |
| Chondroitin Sulfate | 1,000 mg (bovine) | 1,200 mg | 2,500 mg |
| Hyaluronic Acid | 100 mg | — | 100 mg |
| ASU | — | 1,050 mg | 1,000 mg |
| Collagen (hydrolyzed) | 1,000 mg | — | 2,000 mg |
| Silica (orthosilicic acid) | 200 mg | — | 250 mg |
| Vitamin C | 500 mg | — | 1,000 mg |
| Boswellia extract | — | 300 mg | 300 mg |
| Manganese | — | 250 mg | 50 mg |
| Serving size | 58 g | 17.5 g | — |
| Cost per day | ~$1.84 | ~$1.73 | — |
Which One for Your Horse
If your horse works regularly and you want the most glucosamine and MSM per dollar in a single product, buy SmartFlex Ultra. Full dose, no stacking needed, $1.84/day. Done.
If your vet has recommended ASU specifically — maybe your horse has early cartilage changes on imaging, or you’re managing a joint that’s been injected and you want ongoing cartilage protection — Cosequin ASU is the only scored product delivering ASU at full dose. You’re trading glucosamine volume for a unique mechanism of action. That’s a reasonable trade for the right horse.
If you compete at rated shows and the idea of an undocumented supplement makes you nervous, Cosequin ASU’s quality paper trail is the strongest in our database. SmartPak is probably fine. Nutramax can prove it.
For everyone else: SmartFlex Ultra. More of what matters, nearly the same price.
Frequently Asked Questions
Can I combine SmartFlex Ultra and Cosequin ASU?
You could, but you’d be paying $3.57/day and doubling up on glucosamine, MSM, and chondroitin for no extra benefit. Smarter approach: use SmartFlex Ultra for the dose, add a standalone ASU supplement if you want that mechanism. Cheaper and no redundancy.
Is 7,200 mg of glucosamine actually not enough?
It might be fine for some horses — particularly lighter horses or those in light work. The 10,000 mg threshold is based on research for a 500 kg horse. A 400 kg horse in light exercise may respond to less. But if you’re paying $1.73/day for 72% of the target dose when $1.84/day gets you 100%, the economics point to SmartFlex Ultra.
Full audit reports: SmartFlex Ultra | Cosequin ASU