You are at the local pet food store shopping for a new diet for your dog or cat - one that your pet will enjoy and eagerly anticipate at mealtimes; a diet that is nutritionally adequate and will contribute to optimal health and longevity. But when you inspect a diet from the shelf, you notice by-products in the ingredients list.
“By-products” are often criticized in popular media, leading to erroneous assumptions about the quality of diets containing these ingredients. Based on their media portrayal, you may question what by-products are in the first place, and what role they play in your pet’s diet.
What is a by-product?
As defined by the Association of American Feed Control Officials (AAFCO), an organization that publishes pet food labelling and laboratory standards, by-products are “secondary products produced in addition to the principal product”.
In commercial pet foods, by-products are typically animal ingredients such as liver, spleen, and kidneys (organ meats). According to the official AAFCO definition, by-products “do not include hair, horns, teeth and hooves”. Whey protein, a by-product of cheese production, and plant-based by-products such as cornmeal and beet pulp, are also found in pet foods - and in the homes of most consumers.
By-products found in pet foods are items that are not commonly consumed by humans in North America, but they are considered highly desirable in other cultures. Offal, black pudding, and haggis are dishes regularly consumed by humans and fit into the category of animal by-products.
What nutritional benefits do by-products provide?
By-products are a rich source of essential nutrients like protein, fat, vitamins, and minerals. These nutrients play critical roles in the body, supplying the body with energy (calories), providing essential amino acids for development and maintenance of lean body tissue, and supporting the immune system. In fact, many by-products (e.g., liver) are more nutrient-dense than skeletal meats (ie chicken breast or steak)that are typically preferred by North Americans.
"By-products are a rich source of essential nutrients like protein, fat, vitamins, and minerals."
An essential nutrient is one that cannot be synthesized by the animal and must therefore be provided in the diet. Animals (including humans) have requirements for nutrients, not ingredients. Thus, it is more important to consider the nutrients that by-products provide, rather than focusing solely on the ingredient names. Furthermore, the overall quality of ingredients can vary, so the nutritional value of a pet food cannot be measured by the ingredient list on the label.
What are the environmental implications of using by-products in pet feed?
Using by-products in pet food helps reduce waste and improves environmental sustainability by using a greater proportion of the animal for nutritional value. Using only skeletal meats for human and animal consumption creates waste and results in increased demands on livestock populations.
By-products provide an important and concentrated source of essential nutrients to meet our pets’ metabolic needs.
Should I feed my pet a diet that contains by-products?
A diet recommendation for any pet should be based on a combination of factors, including medical history, dietary history, and physical examination findings from your veterinary care team.
Ultimately, the goal is to feed our pets a good quality, complete, and balanced source of nutrition that is species-specific and life-stage appropriate. This goal can be met with or without the inclusion of by-products, provided that the essential nutrients are present in the required amounts and proportions.
By-products can provide an accessible source of essential nutrients, so there are no health advantages gained by avoiding them. Talk to your veterinary care team to collaborate on a nutritional plan for your individual pet.
