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Brand Comparison · 2026

Kirkland Signature vs Purina Pro Plan

Kirkland Signature (Costco's private-label dry food, reportedly made by Diamond Pet Foods, which meets 2 of WSAVA's 5 questions) and Purina Pro Plan (meets all 5 of WSAVA's manufacturer questions, with Sport Performance and Bright Mind lines, at a lower price than Hill's Science Diet or Royal Canin) compared head-to-head on WSAVA manufacturer-quality criteria, AAFCO substantiation, monthly cost, and which dog each is best for in 2026. Purina Pro Plan meets 5 of 5 WSAVA criteria. Kirkland Signature is roughly 65% less than Purina Pro Plan.

The verdict

Purina Pro Plan costs $40-75/month and meets all 5 WSAVA questions with AAFCO feeding tests. Kirkland Signature costs about $20 a month and meets 2 of 5. The $20 to $55 difference buys named nutrition staff at Nestlé Purina, the largest owned manufacturing footprint in pet food, and specialty lines such as Sport Performance. Kirkland Signature's label says "formulated to meet" AAFCO profiles, and Costco does not name its manufacturer.

Kirkland Signature works for a healthy adult when the Costco price decides it and you will confirm the manufacturer yourself. Purina Pro Plan is the better fit for working dogs, seniors and owners who want trial-backed substantiation. Purina ONE also meets all 5 and costs $30-35, so it sits between the two on price. Medical needs go to your veterinarian.

Key differences at a glance

Quick comparison

DimensionKirkland SignaturePurina Pro Plan
Parent companyCostco (reportedly made by Diamond Pet Foods)Nestlé Purina
CategoryMass-market dry kibblePremium dry kibble
WSAVA criteria met2 of 55 of 5
AAFCO substantiationFormulation onlyFeeding trials
Full-time veterinary nutritionistPartialYes
Credentialed formulatorPartialYes
AAFCO feeding trialsNoYes
Owns manufacturing plantsYesYes
Quality control programYesYes
Typical monthly cost (50 lb dog)$20 / month$40 – $75 / month

Costco (reportedly made by Diamond Pet Foods)

Kirkland Signature

Costco's private-label dry food, reportedly made by Diamond Pet Foods, which meets 2 of WSAVA's 5 questions.

Strengths

  • Low price, about $1 a pound for the 25 lb bag, or roughly $20 a month for a 50 lb dog
  • Diamond, the reported maker, publishes a test-and-hold program with certified-lab testing
  • Diamond operates seven US manufacturing facilities and is family-owned

Watch-outs

  • Costco's product page names no manufacturer. Costco's 2025 pet FAQ said Diamond makes the dry foods, but the bag's own maker line was not checked
  • Label says "formulated to meet" AAFCO profiles rather than citing feeding trials
  • No named nutritionist or formulator. Diamond describes only unnamed experts
  • Costco's Nature's Domain grain-free line was named in 29 reports in the FDA's 2019 DCM update. The FDA did not establish that any food caused the disease

Best for: Costco members who want a low-cost dry food and will check the bag's manufacturer line themselves.

Avoid if: You want a named, credentialed nutrition team or feeding-trial substantiation behind the food.

Visit Kirkland Signature ↗

Nestlé Purina

Purina Pro Plan

Meets all 5 of WSAVA's manufacturer questions, with Sport Performance and Bright Mind lines, at a lower price than Hill's Science Diet or Royal Canin.

Strengths

  • Roughly 25-40% cheaper than Hill's at comparable spec
  • Largest owned manufacturing footprint in pet food globally
  • Bright Mind senior cognitive line has peer-reviewed support
  • Sport Performance line designed for working dogs

Watch-outs

  • Mass-market positioning leads to incorrect 'lower quality' perception
  • Easy to confuse with other Purina lines on the shelf, which differ in formulas and price

Best for: Healthy adult dogs without specific medical conditions; budget-conscious owners who still want full WSAVA-compliant quality.

Avoid if: You specifically need a breed-tailored formulation only Royal Canin provides.

Visit Purina Pro Plan ↗

Which is better for your dog?

The right pick depends on your individual dog. Kirkland Signature is the better choice when: Costco members who want a low-cost dry food and will check the bag's manufacturer line themselves. Purina Pro Plan is the better choice when: Healthy adult dogs without specific medical conditions; budget-conscious owners who still want full WSAVA-compliant quality.

On cost, Kirkland Signature is roughly 65% less than Purina Pro Plan at the midpoint of typical premium spec for a 50 lb adult dog. On WSAVA manufacturer-quality criteria, Purina Pro Plan meets 5 of 5 vs 2 of 5 for Kirkland Signature.

Checking one brand rather than the pair? See is Kirkland Signature WSAVA-approved or is Purina Pro Plan WSAVA-approved.

Where to buy

Made your pick?

Check current pricing on whichever brand fits your dog. Prices and promotions change frequently, so it is worth comparing both before you commit to a bag or a subscription.

Shop Purina Pro Plan on Chewy →

Disclosure: these are affiliate links and IntelliBowl may earn a commission at no extra cost to you. Commission does not influence the comparison above. See our methodology.

Personalized recommendation

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Compare these brands against others

Methodology: WSAVA criteria reflect each brand's publicly documented manufacturer-quality practices as of October 2026, scored against the WSAVA Global Nutrition Committee's 5-question rubric. AAFCO substantiation reflects the dominant method used across the brand's main retail product line. Monthly cost reflects typical US 2026 retail for a 50 lb adult dog at premium spec, before autoship discounts. Recommendations are editorial and not influenced by affiliate relationships. See our recommendation methodology for IntelliBowl's quiz-engine ranking logic.