The scores
Eukanuba Puppy Medium Breed: B (75/100) — Chicken, chicken by-product meal, corn, chicken fat, wheat. Fish oil for DHA, fructooligosaccharides (FOS) for prebiotic fiber, medium-breed-targeted calcium and phosphorus.
Eukanuba Adult Medium Breed: C (60/100) — Similar corn and wheat grain base, chicken by-product meal for protein, but without the puppy-specific DHA and prebiotic emphasis.
How the ingredients compare
Puppy top 5: Chicken, Chicken By-Product Meal, Corn, Chicken Fat, Wheat
Adult top 5: Similar — chicken-first with chicken by-product meal, corn, and wheat dominating the carb base.
Both formulas use the legacy Procter & Gamble / Mars Petcare formulation template: fresh chicken at position one for wet-weight protein anchor, chicken by-product meal at position two for concentrated protein density, then corn and wheat as the primary carb base. This formulation template is cost-engineered for mass-market retail — it is neither corn-free, grain-free, nor by-product-free, and both Puppy and Adult variants share these constraints. The meaningful differences show up in positions six through fifteen, where Puppy inserts DHA-specific fish oil and FOS prebiotics.
Where the Puppy formula pulls ahead (by 15 points)
Fish oil for DHA (the main reason): Puppy explicitly adds fish oil (position ten) for brain and retinal development during the 0-12 month neurological window. Adult Eukanuba Medium Breed lacks dedicated DHA emphasis. For growing puppies, the DHA inclusion is directly developmentally supportive — and on our rubric, dedicated fish oil inclusion is a meaningful positive signal.
Fructooligosaccharides (FOS) for prebiotic support: FOS (position 15) supports microbiome development during the 0-6 month gut colonization window. Combined with dried plain beet pulp, the gut-support profile is modest but legitimate. Adult Eukanuba doesn't emphasize prebiotics the same way.
Tighter growth-phase AAFCO compliance: Puppy is formulated to AAFCO growth standards (rather than adult maintenance), with calcium, phosphorus, and caloric density specifically aligned to the 0-12 month developmental window. Medium-breed-targeted kibble size and mineral balance are calibrated for medium-breed puppy growth (10-50 lb projected adult weight).
Natural preservatives: Chicken fat is preserved with mixed tocopherols and citric acid rather than BHA/BHT — a reformulation improvement Puppy carries consistently. Shop on Amazon →
Where the Adult formula holds its own
Maintenance-tuned caloric density: Adult Eukanuba Medium Breed caloric profile is lower than Puppy's — appropriate for adult dogs in the 12+ month range. Feeding a puppy formula to an adult dog risks overconditioning and weight gain. The life-stage match matters operationally.
Mainstream retail availability: Eukanuba Adult Medium Breed is the brand's flagship SKU at chain retailers (PetSmart, Petco, Tractor Supply). For brand-loyal households with adult dogs, availability consistency matters.
Same Mars Petcare manufacturing standards: Both variants share Mars's quality control infrastructure, recall-responsiveness history, and AAFCO compliance testing. The brand's consistency across life stages is a stability signal for households that don't want to change brands at the 12-month transition. Shop on Amazon →
The bottom line
For puppies 0-12 months, Eukanuba Puppy Medium Breed is the right choice — fish oil DHA, FOS prebiotics, and AAFCO-tuned growth profile are developmentally tuned. The 15-point score lead over Eukanuba Adult is genuine. For dogs 12+ months, Eukanuba Adult Medium Breed (C/60) delivers the same brand consistency at an adult-appropriate caloric density, though at a score tier meaningfully below the B/78 premium mainstream alternatives (Merrick, Nutro, Wellness, Canidae, Taste of the Wild). If you are on Eukanuba Puppy and considering options at the 12-month transition, upgrading to a premium grain-inclusive adult (Merrick Classic B/80, Nutro Wholesome Essentials B/77, Wellness Complete Health B/82) will deliver materially better ingredient quality than staying on Eukanuba Adult.