Knowing how much of each ingredient a pet food contains is obviously crucial if you want to really understand how good or bad it might be for your pet.
The trouble is, even when the manufacturer gives a full list of ingredient percentages on the label (which they often do not), they may not necessarily reflect what is actually going into your dog.
This is because any percentages given on the ingredients list have to be the so-called 'mixing bowl' percentages which very often do not reflect the final 'as fed' proportions in the finished product.
Mixing bowl composition
The mixing bowl composition reflects the proportions of the ingredients as they are blended prior to final production.
By law, pet food manufacturers must declare the ingredient list in descending order of their mixing bowl proportions, so biggest first, smallest last.
Think of it like a cookbook recipe but with percentages instead of grams or ounces.
As fed proportions
The as fed composition, on the other hand, describes the proportions of the ingredients in the finished product - the actual composition that your dog eats. It is, arguably, a much better guide of the true nature of a food than the mixing bowl composition.
Why are the mixing bowl and as fed compositions different?
Processing and cooking can have a significant effect on the weight of certain ingredients. This is particularly true when dried ingredients are used in wet foods or when wet (or 'fresh') ingredients are used in dry foods.
A good example is grain in wet pet food. The label might say 10% rice but that is the proportion of dried rice prior to cooking. By the time it has been cooked and rehydrated, the final proportion of rice will likely be closer to 30%.
Conversely, if a dry food is made with 40% fresh meat, once it has been cooked and dehydrated it may only make up less than 15% of the final biscuit.
In these situations, the mixing bowl and as fed proportions can be dramatically different and converting one to another is no simple feat. Fortunately, we've come up with an algorithm to estimate the as fed percentages of the main ingredient groups for you - just look for the pie charts on the pet food product pages.