Protein quality and complementarity of mealworm ingredients for pet food

In a global pet food market valued at nearly 100 billion USD annually¹, and growing at a rate of 5% per annum, increasing humanization of pets and awareness of their health issues is driving a demand for pet food of increasingly high quality². Using DIAAS-like scores to assess the protein quality of pet food ingredients has revealed that Sprÿng’s mealworm-based ingredients are on a par with more conventional premium ingredients.

Measuring protein quality

An important measure of the nutritional value of a food ingredient is its protein quality. This is an evaluation of the extent to which the ingredient can deliver indispensable amino acids (IAAs). Moreover, the requisite quantity of each IAA is dependent on life stage, with growing animals having different needs than adults.

Importantly, it is not sufficient to know that an ingredient simply contains an IAA: it must contain it in a form that can be digested. Digestibility varies between protein sources, and can be compromised by the way an ingredient has been processed, or the co-presence of so-called “anti-nutritional factors” that actively hamper digestion.

“Digestible Indispensable Amino Acid Score” as a measure of protein quality

A useful indicator of the protein quality of an ingredient, in human foods, is the “Digestible Indispensable Amino Acid Score” (DIAAS) — and increasingly, an analogous “DIAAS-like” score is being used to rate pet food ingredients. The ileal digestibility of each IAA in the ingredient is expressed as a percentage of reference dietary requirements for adult and growing animals, as compiled by regulatory bodies such as AAFCO (The Association of American Feed Control Officials).

If every IAA in an ingredient achieves a value above 100% (i.e. greater than the reference value), then the ingredient is considered to be a complete protein source. Otherwise, the ingredient is given a DIAAS-like score corresponding to the value of the lowest-scoring IAA — known as the limiting amino acid (LAA). The LAA in question must be supplemented elsewhere in the diet.

Performance of traditional pet food ingredients

A recent comparative study³ has compiled existing data for various pet foods and used it to calculate the DIAAS-like scores for the ingredients. Currently, two of the most frequently-used protein sources in pet food are corn and chicken: whole corn and corn gluten meal together account for 21% of pet food ingredients, while chicken meat and chicken meals account for another 13%⁴.

Using the AAFCO references, of five corn gluten meal sources reported, the average DIAAS-like score for adult dogs was found to be 40% [range 34-45], and for puppies 37% [34-39]; and of seven whole corn sources, the average scores were 62% [55-75] and 56% [46-65] for adults and puppies respectively. For chicken ingredients, the DIAAS-like scores are quite variable: of three chicken meat sources and five chicken meal sources reported, one of each scored percentages in the 80s, with the remainder scoring lower, in the 50s or 60s. 

The same study found that some of the best-performing animal and plant protein sources are rice, with an average score (for adult dogs) of 93%; salmon meat, at 91%; beef loin, at 89%; and fish meal, averaging 85.5%. These are thus examples of the high protein quality ingredients for which consumer demand is increasing — but they currently represent a much smaller share of the pet food market than corn and chicken, accounting for only 3%, 0.6%, 2% and 0.4% of the market respectively⁵. In general, scores for puppies are lower across the board; among the highest scores were beef loin (81%) and fish meal (range 69-82%).

Mealworm protein is on a par with the highest quality ingredients

No insect ingredients featured in this comparative study; however, another recent study⁶ has directly measured DIAAS-like scores for three of Sprÿng’s mealworm-based ingredients: two defatted meals and one whole meal. All three of these ingredients scored highly for both adult dogs (72%, 79%, 96%) and puppies (83%, 83%, 87%). These scores are comparable to the highest quality animal proteins (beef, pork, salmon), and higher than poultry and most common plant proteins.

Indeed, with its score of 96%, one of Sprÿng’s defatted mealworm meals was one of the very highest scorers for adult dogs; and with reference to pups, all three mealworm ingredients scored higher than most of the animal and plant ingredients for which scores are available. The same study also calculated DIAAS-like values for cats: with reference to adult cats, all three were found to be complete protein sources. (For kittens, the scores were somewhat lower, at 64.1-77.6%, but comparable to available values for traditional animal proteins.⁷)

Limiting amino acid and complementarity of protein sources

For all three mealworm ingredients, the LAA for adult dogs was methionine, and for puppies threonine. These are the same amino acids that are limiting for more traditional animal protein sources in pet foods — consequently, any required supplements are already standard within the industry. Furthermore, for all three mealworm ingredients, with reference to adult dogs, methionine was the only amino acid to achieve a score less than 100% – meaning that once the standard methionine supplement has been added, the protein source becomes complete.

Hence, there is no technical barrier to the use of mealworm protein as a pet food ingredient. It is also interesting to note that the LAA for corn — currently the most common pet food ingredient — is not methionine, but either lysine or tryptophan. Thus, there is a complementarity between corn and mealworm proteins: when combined in the appropriate proportions, they become a complete protein source, obviating the need for any supplement.

Conclusion

From a nutritional standpoint, then, there is excellent reason to embrace mealworm as a protein of choice for our pets, either on its own or in combination with other ingredients. From a practical standpoint, Sprÿng’s mealworm meals are consistent in composition, and can easily be combined with other ingredients, opening the door to blended products that take advantage of the complementarity between mealworm protein and plant sources such as corn.

Moreover, by supplementing, say, a chicken or lamb meal-based pet food with mealworm ingredients, we are not only improving the nutritional quality of the food, but also reducing our reliance on poultry and livestock farming. So while our goal at Sprÿng is to provide the highest quality diet possible for our beloved companion animals, our pet foods also offer added value for the environment.

1. https://www.grandviewresearch.com/industry-analysis/pet-food-industry
2. https://www.grandviewresearch.com/industry-analysis/pet-care-market/toc
3. Templeman et al. (2022) J. Animal Sci. 100. doi: 10.1093/jas/skac279
4. https://ifeeder.org/pet-food-report/
5. https://ifeeder.org/pet-food-report/
6. Smola et al. (2023) J. Animal Sci. 101. doi: 10.1093/jas/skad012
7. Oba et al. (2019) J. Anim. Sci. 97. doi: 10.1093/jas/sky461