Why does my vet keep recommending the same brands?

The short answer

Your vet isn't getting kickbacks. They're applying a set of manufacturer evaluation criteria published by the World Small Animal Veterinary Association (WSAVA), and only a handful of companies consistently pass all six questions. Brands like Hill's Science Diet, Purina Pro Plan, and Royal Canin invest heavily in full-time veterinary nutritionists, rigorous feeding trials, and published research. That's what separates them in the eyes of evidence-based veterinary nutrition.

This doesn't mean no other brand is worth feeding. It means the criteria exist, and any company, large or small, can meet them. Here's what those criteria actually are.

The WSAVA's six questions

The WSAVA Global Nutrition Committee developed a straightforward framework for evaluating pet food manufacturers. These aren't pass-fail ratings of individual products. They're questions about the company behind the food. The logic is simple: good processes produce more consistently good food than good marketing copy does.

The six questions are:

1. Does the company employ a full-time, qualified nutritionist? A board-certified veterinary nutritionist (DACVN) or someone with a PhD in animal nutrition, employed full-time (not contracted per-project).
2. Does a qualified nutritionist formulate the diets? Formulation should involve someone with deep credential-backed nutrition expertise, not just a general food scientist.
3. Where are the foods manufactured? Is production in-house or outsourced? Manufacturers with their own facilities have tighter quality control.
4. What quality control measures are used? This includes pre-production testing of raw ingredients, in-process testing, and finished product testing.
5. Can the company provide any requested nutrient value for their products? Transparency here matters. A company that can't or won't share nutrient data is a concern.
6. Has research been conducted on the product? This includes feeding trials, digestibility studies, and peer-reviewed publications.

Why feeding trials matter so much

The AAFCO nutritional adequacy statement on every bag tells you whether a food meets nutrient minimums, but it doesn't tell you how. There are two methods: formulation and feeding trials. Formulation means the recipe was calculated to meet standards. Feeding trials mean actual animals ate the food for a minimum duration and were monitored for health outcomes.

Feeding trials catch things formulation can't. A food can look nutritionally complete on paper while containing nutrients in forms the animal can't absorb, or in combinations that cause problems over time. Feeding trials are more expensive and time-consuming, which is why many smaller brands rely on formulation alone. Brands that conduct feeding trials are held to a meaningfully higher standard.

Look for the phrase "animal feeding tests" on the AAFCO statement. That indicates a feeding trial was used. "Formulated to meet" indicates calculation only.

What vets are actually seeing

Veterinary nutritionists have direct access to manufacturer data. They can call the company, ask for the nutrient profile of a specific product, and get a real answer. For most smaller brands, that call doesn't go anywhere useful. For brands like Purina and Hill's, there are dedicated nutrition hotlines staffed by credentialed professionals.

Vets also see the outcomes. When a patient comes in with dilated cardiomyopathy linked to a specific diet, or when a cat on a boutique food develops a taurine deficiency, those cases inform recommendations. The recommendation to stick with WSAVA-criteria-passing brands isn't born from brand loyalty. It comes from pattern recognition over clinical experience.

Does this mean other brands are lower quality?

Not necessarily. There are smaller, independent brands that invest in nutritionists, publish research, and produce high-quality food. The WSAVA criteria don't favor large companies by design. They favor transparency and rigor. A small company that employs a full-time DACVN and conducts feeding trials would satisfy the criteria just as well as a multinational.

What the criteria do filter out are brands that rely primarily on marketing, trend ingredients, or curated ingredient lists without the nutritional infrastructure to back them up. That's not about size. That's about priorities.

If you're evaluating a brand outside the commonly recommended ones, try contacting the company directly and asking the six WSAVA questions. How they respond tells you a great deal.

A note on cost and accessibility

Hill's, Purina Pro Plan, and Royal Canin are not cheap, but they're also not the most expensive foods on the shelf. In many cases, less expensive foods from these manufacturers outperform pricier boutique options on the criteria that actually matter to nutrition. Price is not a proxy for quality. WSAVA-aligned criteria are.

If cost is a genuine barrier, Purina Pro Plan in particular offers a range of price points and is one of the most extensively researched brands available. Your vet's recommendation isn't aimed at upselling. It's aimed at reducing uncertainty about what your pet is eating.

Content based on WSAVA Global Nutrition Committee guidelines and NAVC Pet Nutrition Coach Certification coursework.

KibbleLab Explains articles are educational, and are not veterinary advice. Before starting an elimination diet, a weight plan, or any major diet change, talk to your veterinarian.