Effects of moderate-protein and high-protein diets, including mealworm meal or poultry by-product meal, on immunological variables in healthy adult dogs.

Background: Insect meals are increasingly being used as an ingredient in diets for dogs. However, little is known about their effects on the immune function of the animals. In the present investigation, mealworm meal was included in two complete diets with either a moderate or a high protein concentration (3.47% or 5.45% nitrogen in dry matter). Two diets with comparable protein levels (3.66% and 5.17% nitrogen in dry matter), but based on poultry by-product meal, served as control treatments. The diets were offered to 10 healthy adult beagle dogs, using a randomized crossover design. Each diet was fed for 4 weeks. Fasting blood samples were collected on day 24 of each feeding period for immune cell phenotyping, proliferation and phagocytosis assays, as well as for the measurement of plasma immunoglobulin (Ig) concentrations.

Results: All dogs remained healthy throughout the study. The percentages of CD4⁺ cells in the blood of the dogs were lower, and the percentages of CD8⁺ cells were higher, when the diets with mealworm meal and the high-protein diets were fed. An interaction effect between the dietary protein source and protein level could be detected for the phagocytic activity of blood granulocytes as well as for the plasma concentrations of IgA and IgE.

Conclusions: Both the protein source and protein level had an impact on the immune system of the dogs. The observed immunological changes were, however, not linked to any adverse food reactions, suggesting that the clinical relevance of these findings is likely small. Further studies should evaluate the immunological properties of dietary mealworm meal also in diseased animals, particularly in allergic dogs.