Comparing Pet Food Properly: Dry Matter, Cost Per Day and Labels

Pet food is the largest recurring cost of owning an animal, and it is priced and labelled in ways that make comparison difficult. Two calculations remove most of the confusion.

Cost per day, not price per bag

Take the feeding guide for your animal's weight, find the grams per day, and divide the pack weight by that. Now divide the price by the number of days. That figure is comparable across brands and pack sizes, and it frequently reverses which product looks cheaper.

A denser, more calorie-rich food is fed in smaller amounts, so a higher price per kilogram can still be a lower cost per day.

Dry matter, for comparing wet with dry

The analytical constituents panel gives percentages including water. Wet food is mostly water, so its protein percentage looks far lower than dry food even when the actual nutrition is similar. To compare, subtract the moisture percentage from 100 to get the dry matter, then divide the nutrient percentage by that.

Without this step, comparing a wet and a dry food on their headline protein figures is meaningless.

What the ingredients list tells you

• Order is by weight before cooking. Fresh meat listed first contains a lot of water that is removed during processing, so it may contribute less to the finished food than its position suggests. A named meal is already dehydrated.
• Named versus generic proteins. "Chicken" identifies the species; "meat and animal derivatives" does not. The generic term is not automatically poor quality, but it is less informative and can vary between batches.
• Ingredient splitting. Listing several forms of the same base ingredient separately moves each further down the list. Worth noticing.

Claims that are regulated, and claims that are not

• "Complete" means the food is formulated to be the animal's sole diet. "Complementary" means it is not. This distinction is defined and is the most important word on the pack.
• Flavour wording is governed by minimum content rules that vary by phrasing — "chicken dinner", "with chicken" and "chicken flavour" can mean very different quantities.
• "Premium", "natural", "human grade" — marketing terms with no consistent legal definition in most markets.
• "Grain free" describes what is absent, not what makes a food suitable. It is a choice, not a quality tier.

Changing foods

Transition over a week or more by mixing an increasing proportion of the new food. Sudden changes are the most common cause of digestive upset, and they also make it impossible to tell what caused a reaction.

Buy the smallest size of anything new. Animals refuse foods, and a bulk order of something refused is a total loss.

Storage

Dry food degrades once opened as fats oxidise. Keep it in the original bag, which is designed as a barrier, inside a container rather than tipped loose into one. Buy a quantity your animal will finish within the recommended window rather than the largest bag available.

Before you order

Check the best-before date on discounted stock. Check whether the retailer accepts returns on opened food, which most do not. And if your animal has a diagnosed condition, treat food as a veterinary question rather than a shopping one — prescription diets exist for clinical reasons.