Short answer:  Kirkland’s is better. But by how much? I think it’s “better” enough to be my pick between the two.

I want my middle aged dog to be the healthiest, given what you know about the two diets, which diet should provide statistically better nutrition for my dog?

If you make me choose only between Sam’s and Kirkland, I’d rank them:

🥇 Kirkland — slight preference
The 0.40% omega-3 vs 0.20% is meaningful to me for a middle-aged dog, and I like the salmon oil/fish-derived lipid profile, 180 IU/kg vitamin E, slightly higher taurine, and broader fermentable-fiber/prebiotic system. I would not choose Sam’s merely because its glucosamine is 400 mg/kg—the amount consumed is modest compared with therapeutic joint supplementation. And its 40× larger probiotic CFU guarantee looks spectacular on paper, but CFU count alone doesn’t establish superior clinical benefit.

🥈 Member’s Mark — still a reasonable complete diet on its label
I like the explicitly guaranteed Ca/P, glucosamine/chondroitin and the substantial B. coagulans guarantee. But peas and chickpeas appear very prominently, which makes me less enthusiastic about it as a lifelong default diet when there’s no reason the dog needs grain-free.

Me: “Show me everything to know about ingredients and guaranteed analysis on Maker’s Mark Sam’s Grain Free dog food Salmon and Sweet Potato”

Bob:

Doc — I found it. I think you mean Member’s Mark Grain Free Salmon & Sweet Potato, the Sam’s Club house-brand food. Sam’s current listing gives us an unusually detailed ingredient list and guaranteed analysis, so there’s quite a bit we can say about it. Samsclub.com

Member’s Mark Grain Free Salmon & Sweet Potato — Sam’s Club

What’s actually in it

The current ingredient list is:

Salmon (source of DHA), menhaden fish meal (source of glucosamine and chondroitin sulfate), sweet potatoes, dried whole peas, chickpeas, canola oil (preserved with mixed tocopherols), brewers dried yeast, dried yeast, dehydrated alfalfa meal, natural flavor, dicalcium phosphate, inulin, dried tomato pomace, vitamins, potassium chloride, salt, dried carrots, minerals, dried kelp, choline chloride, taurine, citric acid, mixed tocopherols, dried Bacillus coagulans fermentation product, rosemary extract. Samsclub.com

That’s important because this appears to be a newer formulation. I found older third-party ingredient listings that differ substantially—including one with chicken fat—so I would use the current Sam’s Club formulation above when evaluating a bag being sold now. Trash Panda

And remember that ingredients are listed by weight before processing, not by their nutritional contribution to the finished kibble. Fresh salmon contains a lot of water, whereas menhaden fish meal is already concentrated. So “#1 ingredient salmon” doesn’t necessarily mean salmon provides more finished-product protein than everything else combined. AAFCO

Guaranteed analysis

Those are as-fed guarantees, and minimums aren’t necessarily the actual average nutrient concentrations. That’s a distinction worth making—the food may contain appreciably more than 28% protein or 14% fat. AAFCO explains that guarantees are deliberately set as minimums or maximums to account for normal batch variation. Samsclub.com

On a dry-matter basis, using the maximum 10% moisture figure, those first numbers work out to approximately:

Protein ≥31.1% DM; fat ≥15.6% DM; fiber ≤4.4% DM; calcium ≥1.33% DM; phosphorus ≥1.11% DM.

The minimum stated Ca:P ratio is 1.2:1, which looks quite reasonable.

A secondary source reports 3,470 kcal/kg, 1,574 kcal/lb and about 342 kcal/cup. I would regard those calorie figures as somewhat less authoritative than the Sam’s Club label information because I don’t see the calorie statement reproduced on Sam’s current product page. KibbleLab

Protein sources — this is where it gets interesting

The first two ingredients are genuinely good animal-protein ingredients:

Salmon supplies fish protein, fat and DHA, while menhaden fish meal is a concentrated fish-protein/mineral ingredient and contributes omega-3 fatty acids. Fish meal being second is actually more nutritionally significant to me than the marketing claim that fresh salmon is first.

But then ingredients 4 and 5 are:

dried whole peas + chickpeas.

Both contribute carbohydrate, fiber and protein. Consequently, you cannot look at the 28% crude protein guarantee and conclude that it’s 28% fish-derived protein. Some unknown proportion comes from legumes, yeast and alfalfa.

That’s not necessarily bad, but it’s an important distinction if you’re evaluating this as a “salmon-based high-protein food.”

Carbohydrate

The manufacturer doesn’t guarantee ash, so we can’t calculate carbohydrate accurately from the label.

Using nitrogen-free extract:

Carbohydrate ≈ 100 − protein − fat − moisture − fiber − ash.

We know everything except ash.

If the finished food were, for example, roughly 7–9% ash, we’d estimate carbohydrate at approximately 35–37% as fed, or roughly 39–41% of dry matter.

That’s only an estimate—not a label value. The ingredients make it obvious that this is still a fairly substantial carbohydrate diet: sweet potato + peas + chickpeas comprise three of the first five ingredients.

The fat profile

This is pretty decent:

14% minimum crude fat isn’t excessively high for an ordinary kibble.

There’s 1.8% minimum omega-6 and 0.20% minimum omega-3, giving a maximum implied omega-6:omega-3 ratio around 9:1 based on those minimum guarantees—but because both are minimums, you can’t calculate the true ratio from the guaranteed analysis.

I like seeing a specific DHA guarantee of ≥0.05% rather than just vague “contains omega-3” marketing.

One thing I’d note: canola oil is ingredient #6. So the fatty-acid profile isn’t simply “fish oil because it’s salmon food.” Some substantial lipid contribution may be plant-derived.

Joint claims

The food guarantees:

Glucosamine 400 mg/kg
Chondroitin sulfate 400 mg/kg

Those numbers sound impressive on a bag, but they are nutritional amounts, not what I’d consider therapeutic joint-supplement dosing.

At ~342 kcal/cup, a 60-lb dog eating around three cups gets roughly 300-ish grams of food depending on kibble density, which would supply only about 120 mg each of glucosamine and chondroitin if the food is at the guaranteed minimum.

So I’d call those nice extras, not a substitute for a therapeutic joint product.

Digestive ingredients

There are several things here that I actually like:

Inulin — soluble/prebiotic fiber.

Dried tomato pomace — fiber source with some fermentable components.

Brewers dried yeast / dried yeast — protein and potential functional components, although the exact nutritional contribution isn’t specified.

Bacillus coagulans — actual guaranteed probiotic at 80 million CFU/lb.

That probiotic number is modest compared with therapeutic veterinary probiotics, but at least they’re guaranteeing an organism and viable count, rather than simply putting “probiotics!” on the front of the bag.

Taurine

This one is particularly interesting because of the formulation:

Taurine ≥0.10% = ≥1,000 mg/kg food.

That’s a meaningful inclusion.

However—and this is important—adding taurine doesn’t automatically eliminate the diet-associated DCM question. Most dogs reported with diet-associated DCM haven’t simply been taurine deficient, and some dogs with normal taurine concentrations have improved after dietary change. Tufts University Sites

The thing that gives me pause: peas + chickpeas

This is the biggest issue I see with this formula.

It’s explicitly grain-free, with:

#3 sweet potato
#4 dried whole peas
#5 chickpeas

That’s exactly the general formulation pattern that has attracted attention in diet-associated/non-hereditary DCM research.

That does not mean “peas cause DCM” or that this food has been demonstrated to cause DCM. FDA specifically says it has not established that legumes are inherently dangerous and has not established a definitive causal relationship. But most diets associated with reported non-hereditary DCM cases have had pulses such as peas/lentils/chickpeas high in the ingredient list. U.S. Food and Drug Administration

And the June 2026 update from Tufts’ veterinary nutrition group says diet-associated DCM remains an active concern, particularly involving nontraditional diets containing pulses. Tufts University Sites

So for me, that’s the elephant in the kibble bag.

Unless I specifically needed grain-free feeding for an individual dog, I don’t see a nutritional advantage to removing grain and replacing it with a substantial pea/chickpea fraction.

Is it really “limited ingredient”?

Sam’s calls it a Limited Ingredient Diet. Samsclub.com

I’d qualify that.

Its major animal protein sources are unusually straightforward—salmon and menhaden fish meal—and the current formula does not list chicken, chicken meal or chicken fat. That’s potentially useful for a dog in which you’re simply trying to avoid poultry.

But this isn’t what I’d use as a true veterinary elimination diet for diagnosing food allergy. There’s natural flavor, multiple plant proteins, yeast ingredients, and the company specifically warns that it’s manufactured in a facility processing foods containing other ingredients and that trace amounts can occur. Samsclub.com

So:

Poultry-free commercial diet? Yes, according to the current formulation.
Diagnostic elimination diet? No.

Nutritional adequacy

This is a strong point.

Sam’s states that it’s formulated to meet AAFCO Dog Food Nutrient Profiles for all life stages, including growth of large-size dogs (70 lb or more as an adult). Samsclub.com

That’s more demanding than an adult-maintenance-only claim.

Notice the word “formulated,” though. The statement presented by Sam’s says formulated to meet the nutrient profiles; it does not say the food passed an AAFCO feeding trial. Those aren’t equivalent claims.

Other little things worth noticing

There are no added corn, soy or wheat, and no artificial flavors or colors according to Sam’s. The preservatives are primarily mixed tocopherols, citric acid and rosemary extract rather than synthetic antioxidant preservatives such as BHA/BHT. Samsclub.com

The mineral package includes several amino-acid complexes—zinc, iron, copper and manganese—in addition to conventional mineral salts. That’s a perfectly respectable approach to trace-mineral supplementation.

It also contains dried kelp, although there’s no iodine guarantee beyond the presence of calcium iodate in the mineral mix, so I wouldn’t infer any clinically meaningful thyroid benefit from the kelp.

And “natural flavor” is deliberately nonspecific. The ingredient list doesn’t tell us exactly what that flavor source is.

My veterinary read of the formula

On the conventional label metrics, this is a surprisingly respectable $38/30-lb food. You’ve got salmon + named fish meal at #1 and #2, 28/14 protein/fat, DHA, taurine, calcium and phosphorus guarantees, omega-3/6 guarantees, a probiotic guarantee, and an all-life-stages/large-breed-growth AAFCO formulation statement. At Sam’s current listed $37.98 for 30 lb ($1.27/lb), there’s a lot of nutrition on paper for the money. Samsclub.com

The one thing that stops me from saying “hell yes, that’s an excellent everyday food” is the grain-free architecture. Sweet potato → peas → chickpeas that high on the ingredient deck is precisely the formulation choice I don’t see a compelling reason to make for the average healthy dog given what we currently know—and don’t know—about diet-associated DCM.

So if you asked me, “Is there anything crappy or obviously nutritionally deficient about this food?” I’d say no.

If you asked me, “Would you choose it over an otherwise comparable salmon diet containing rice/oats instead of a large pulse load?” I’d choose the grain-inclusive diet, assuming there’s no particular medical reason not to.

There’s actually a GREAT 60-second video hiding here: “This $38 Sam’s Club dog food looks shockingly good on the label. So why wouldn’t I automatically recommend it?” The peas/chickpeas/DCM wrinkle gives you a terrific reveal.

Absolutely, Doc. One quick naming correction: I believe you mean Member’s Mark (Sam’s Club), not Maker’s Mark—Maker’s Mark would make feeding time considerably more exciting. 😄

I pulled the current U.S. product information from Sam’s Club and Costco because both formulas have changed over time. This comparison is for Member’s Mark Grain Free Salmon & Sweet Potato versus the current Kirkland Signature Nature’s Domain Salmon & Sweet Potato. Samsclub.com

Side-by-side

Those are label guarantees—not necessarily the foods’ actual analyzed concentrations. Samsclub.com

The fiber difference is more interesting than the 4% vs. 4%

Both guarantee ≤4% crude fiber, but that doesn’t tell us soluble versus insoluble fiber.

Member’s Mark contains inulin, which is a soluble, fermentable prebiotic fiber. It also contains dried tomato pomace and alfalfa, which contribute additional mixed/mostly insoluble fiber. The label specifically promotes prebiotic fiber. Samsclub.com

Kirkland contains dried chicory root, a natural source of inulin/fructans and therefore a soluble fermentable prebiotic fiber. It also contains dried beet pulp, which is particularly interesting nutritionally because it supplies a mixture of fermentable and less-fermentable fiber. Peas and flaxseed add additional fiber. Costco specifically identifies dried chicory root as its natural prebiotic. Costco

So neither manufacturer gives us an actual soluble-fiber percentage. We can’t legitimately say, for example, “Sam’s has 2% soluble fiber and Kirkland has 1%.” But ingredient-wise:

Sam’s: inulin is the obvious dedicated soluble/prebiotic fiber.

Costco: chicory root + beet pulp give it a somewhat broader-looking fermentable-fiber system.

Glucosamine/chondroitin: big difference

This one favors Member’s Mark on the label.

Its menhaden fish meal is specifically identified as the source of glucosamine and chondroitin sulfate, and Sam’s actually guarantees:

Glucosamine ≥400 mg/kg
Chondroitin sulfate ≥400 mg/kg Samsclub.com

Kirkland’s current formula contains salmon meal and fish meal, which can naturally contribute glucosamine/chondroitin, but neither glucosamine nor chondroitin is listed in its guaranteed analysis. Costco therefore makes no quantitative guarantee that lets us compare it to the 400/400 mg/kg Sam’s numbers. Costco

For perspective, Sam’s 400 mg/kg means 40 mg per 100 g of food. That’s a nice nutritional inclusion, though it’s nowhere near what I’d consider a therapeutic joint-supplement dose for a large arthritic dog.

Probiotics — these are VERY different

This may be the most striking formulation difference.

Member’s Mark uses one organism:

Bacillus coagulans — ≥80,000,000 CFU/lb

That’s a spore-forming organism, which makes a lot of sense technologically in an extruded kibble because Bacillus spores are comparatively resistant to manufacturing and storage conditions. Samsclub.com

Kirkland uses five organisms:

Lactobacillus plantarum, Bacillus subtilis, Lactobacillus acidophilus, Enterococcus faecium and Bifidobacterium animalis.

But the total guarantee is only:

≥2,000,000 CFU/lb total. Costco

So this is a funny comparison:

Sam’s = one strain/species, 80 million CFU/lb.
Costco = five organisms, 2 million CFU/lb total.

On the guaranteed numbers, Member’s Mark provides 40× the CFU/lb.

That does not automatically mean “40× better probiotic effect”—strain, viability, dose at consumption, and demonstrated clinical effect matter—but quantitatively it’s a huge difference.

Vitamin/mineral mix

Here’s where the formulas diverge more subtly.

Member’s Mark vitamin premix:
Vitamin E, niacin, calcium pantothenate, vitamin A, riboflavin, thiamine, pyridoxine/B6, folic acid and B12. It also contains choline chloride separately. Samsclub.com

Kirkland vitamin additions:
Vitamin E, thiamine, vitamin A, biotin, niacin, calcium pantothenate, pyridoxine/B6, B12, riboflavin, vitamin D3, and folic acid, plus choline chloride. Costco

The ingredient declaration therefore looks more explicit/complete on Kirkland for biotin and D3, although absence from the Member’s Mark vitamin-premix parenthetical doesn’t by itself prove that the finished diet lacks nutritionally adequate amounts. Both are formulated as complete diets rather than vitamin supplements.

The mineral strategies are similar but not identical. Both use a mixture of inorganic minerals and more bioavailable organic/chelated forms. Sam’s lists zinc, iron, copper and manganese amino-acid complexes; Kirkland lists iron, zinc, copper and manganese proteinates along with conventional mineral salts. Samsclub.com

The actual ingredient decks

The front ends of the formulas are quite different:

Member’s Mark:
Salmon → menhaden fish meal → sweet potatoes → whole peas → chickpeas → canola oil → brewer’s dried yeast → dried yeast → alfalfa → natural flavor → dicalcium phosphate → inulin → tomato pomace… Samsclub.com

Kirkland:
Salmon → salmon meal → sweet potatoes → potatoes → peas → fish meal → canola oil → pea flour → beet pulp → natural flavor → flaxseed → salmon oil… Costco

That produces a couple of meaningful distinctions.

Sam’s is more legume-heavy: peas + chickpeas fairly high on the deck.

Kirkland is more potato-heavy: sweet potato + potato, followed by peas and later pea flour.

Kirkland also explicitly adds salmon oil, flaxseed and fish meal, which fits nicely with its substantially higher guaranteed omega-3 concentration.

And that shows up on the label:

Omega-3: Kirkland 0.40% vs Sam’s 0.20% — double.

Omega-6 is also higher: 2.6% vs 1.8%. Costco

Antioxidant/plant extras

Kirkland has the more conspicuous “fruit and botanical” tail: blueberries, raspberries, tomatoes, chicory root and yucca.

Member’s Mark has carrots, tomato pomace, kelp and rosemary extract, along with alfalfa.

I wouldn’t put enormous nutritional weight on blueberries appearing that far down an ingredient list, but they are genuine formulation differences.

My read of the two formulas

They’re surprisingly close in the basic macronutrients, but they’re not clones.

Member’s Mark has the advantage if you’re specifically looking at: higher protein (28 vs 27%), guaranteed calcium/phosphorus, guaranteed glucosamine + chondroitin, and a dramatically higher labeled probiotic CFU count.

Kirkland has the advantage if you’re looking at: slightly higher fat, 2× the guaranteed omega-3, higher omega-6, higher vitamin E, higher selenium, slightly higher taurine, a five-organism probiotic blend, salmon oil + flaxseed, and what I think is the more interesting mixed prebiotic/fermentable-fiber setup with chicory root + beet pulp.

One thing I’d not conclude is that Kirkland “doesn’t contain glucosamine” just because it isn’t guaranteed. Fish meals naturally contain some. The accurate statement is that Sam’s guarantees 400 mg/kg glucosamine and 400 mg/kg chondroitin; Costco provides no labeled quantitative guarantee.

Likewise, both say 4% crude fiber, but neither publishes enough information to quantitatively compare soluble fiber.

If I were choosing between the two strictly from these labels for a normal healthy dog, Kirkland’s omega-3/fatty-acid profile catches my eye; Member’s Mark’s 80-million-CFU Bacillus coagulans guarantee and explicit glucosamine/chondroitin guarantees catch my eye in the other direction. They’re much less identical than the Salmon & Sweet Potato branding makes them sound.

Member’s Mark Salmon & Sweet Potato — Sam’s Club
Kirkland Nature’s Domain Salmon & Sweet Potato — Costco

Compare on Glucosamine Claims:

Member’s Mark, Doc—pretty clearly, based on what the labels actually guarantee.

Member’s Mark Salmon & Sweet Potato guarantees 400 mg/kg glucosamine + 400 mg/kg chondroitin sulfate. Samsclub.com

The current Kirkland Nature’s Domain Salmon & Sweet Potato formula doesn’t guarantee either glucosamine or chondroitin at all. Its guaranteed analysis lists protein, fat, fiber, DHA, omegas, taurine, minerals, vitamin E and probiotics, but no glucosamine/chondroitin. Costco

So:

One important wrinkle: 400 mg/kg isn’t a huge therapeutic dose. At roughly 342 kcal/cup, a middle-sized dog eating, say, 300 g/day would receive only about 120 mg glucosamine + 120 mg chondroitin/day from Member’s Mark. So I regard this as a nice nutritional extra, rather than a substitute for a properly dosed joint product when we’re actually treating OA.

But strictly answering “which food gives me the better glucosamine/chondroitin package?” — Member’s Mark wins easily.

Compare on Probiotic Claims:

Both do, Doc — but Member’s Mark is more purely a “soil-based probiotic” approach.

The key is Bacillus species. These are spore-forming organisms, commonly grouped under the marketing term soil-based organisms (SBOs).

• Member’s Mark: Bacillus coagulans — 80 million CFU/lb. This is essentially its probiotic strategy: a high-count, spore-forming/SBO-type probiotic.
• Kirkland Nature’s Domain: contains Bacillus subtilis, so yes, it also contains an SBO-type probiotic. But it combines it with Lactobacillus plantarum, L. acidophilus, Enterococcus faecium, and Bifidobacterium animalis. The entire five-organism mixture is guaranteed at 2 million CFU/lb, and Costco doesn’t disclose how much of that is B. subtilis. Costco

So if what you’re specifically looking for is a substantial dose of a spore-forming/“soil-based” probiotic, I’d pick Member’s Mark. Its B. coagulans at 80 million CFU/lb is a much more deliberate SBO-style inclusion than Kirkland’s small mixed-probiotic package.

And that’s actually another point that makes Member’s Mark more interesting than I initially gave it credit for in our overall comparison: 400 mg/kg glucosamine + 400 mg/kg chondroitin AND the high-dose spore-forming probiotic are two legitimate advantages for a middle-aged dog.

Compare on Fiber / Soluble Fiber

Yes, Doc. On soluble/fermentable fiber specifically, I favor Kirkland. But there’s an important limitation: neither manufacturer publishes an actual soluble-fiber percentage, so we have to compare the fiber sources rather than pretend we have numbers that aren’t available.

Why I give Kirkland the edge

Member’s Mark has inulin, which is a very good fermentable soluble fiber/prebiotic. It selectively feeds intestinal bacteria and can increase production of short-chain fatty acids. Its tomato pomace also supplies a mixture of fiber types. The formula additionally contains peas, chickpeas and alfalfa. Samsclub.com

Kirkland has dried chicory root, which is itself an excellent source of inulin-type fructans, so it already gives you essentially the same category of highly fermentable prebiotic fiber. Costco specifically identifies the chicory-root fiber as its prebiotic for supporting intestinal bacteria. Costco

But Kirkland then adds something Member’s Mark doesn’t have:

Beet pulp

That’s why I’d favor Kirkland’s fiber system.

Beet pulp is a moderately fermentable mixed fiber. It provides a different fermentation profile than highly fermentable inulin/chicory alone. In practical canine nutrition, I like that combination because you’re getting something closer to:

chicory/inulin → highly fermentable prebiotic substrate

plus

beet pulp → moderately fermentable fiber

plus

pea/flax fiber → additional mixed/less-fermentable fiber

Kirkland’s ingredient list confirms dried beet pulp fairly high in the formula—9th ingredient—whereas dried chicory root appears much farther down. Costco

Member’s Mark has inulin as ingredient #12, followed by dried tomato pomace. Samsclub.com

So for your middle-aged dog…

If we’re keeping score on the categories we’ve discussed:

Glucosamine/chondroitin → Member’s Mark 🏆

Spore-forming/”soil-based” probiotic quantity → Member’s Mark 🏆

Omega-3 concentration → Kirkland 🏆

Soluble/fermentable fiber system → Kirkland 🏆

And on that last one, I wouldn’t say Kirkland necessarily has more soluble fiber—we don’t have the analytical data to establish that. I’d say Kirkland has the fiber formulation I prefer, principally because chicory root + beet pulp gives a nice combination of highly fermentable prebiotic and moderately fermentable fiber.

That distinction matters: 4% crude fiber tells us almost nothing about the physiologic behavior of that fiber. Two foods can both say 4% and behave quite differently in the colon.