Effects of black soldier fly larvae on the fecal characteristics, skin and coat health markers, immune function, and oral health measures of healthy adult cats

Abstract Black soldier fly larvae (BSFL) is a recently approved alternative protein source for dog and cat foods and treats in the United States, but research in cats remains limited. The objective of this study was to determine the effects of BSFL on the serum chemistry, hematology, skin and coat health markers, fecal characteristics, immune function, and oral health measures of healthy adult cats. Twenty-five adult cats (17 females and 8 males; 6.28 ± 0.27 yr; 4.50 ± 0.18 kg) were used in a completely randomized design. The study was composed of a 21-d baseline period and a 70-d experimental period. During the baseline period, all cats were fed a chicken meal-based control diet (35% of diet). After baseline, cats were assigned to 1 of 2 experimental diets: control diet (n = 12) or a BSFL-containing diet (20% whole BSFL meal and 24% chicken meal; n = 13). At baseline, teeth were cleaned by a veterinarian. Breath samples were analyzed for odor components, salivary pH was measured, and blood samples were collected after baseline cleaning, day 35, and day 70. Feces were scored, fecal samples were collected, skin was assessed, and hair was collected at baseline and day 70. Oral health indicators were assessed by a board-certified veterinarian at day 70. Data were analyzed using the mixed models procedure of SAS, testing for effects of diet (oral microbiota) or diet, time, and diet*time (variables measured over time), with P < 0.05 being significant. Diet*time interactions (P < 0.05) were noted for blood calcium, cholesterol, and triglyceride concentrations and fecal characteristics, metabolite concentrations, and microbiota populations. Some hematologic measures were affected by time, but none were impacted by diet. Cats fed BSFL had lower (P < 0.05) fecal pH, dry matter, and phenol, indole, and branched-chain fatty acid concentrations, and greater (P < 0.05) fecal scores and short-chain fatty acid concentrations. Fecal microbiota populations were affected by BSFL, with alpha diversity, beta diversity, and >20 bacterial genera being different between groups. Immune markers, skin and hair measures, salivary pH, breath odor, and oral microbiota and health measures were unaffected by the diet. In conclusion, a 20% dietary BSFL inclusion had clear effects on the fecal characteristics, metabolites, and microbiota of healthy adult cats, shifting most outcomes in a positive direction. Inclusion of BSFL had mild effects on serum metabolites and did not significantly affect the other variables measured.