Protein production through precision fermentation is an attractive option to reduce animal use in food production. This study focused on the safety and digestibility of food containing a test ingredient, brewed lamb protein (Saccharomyces cerevisiae expressing a lamb protein), at inclusion levels of 0% (control), 15%, 30%, or 40% were evaluated over 182 days in 40 dogs. No significant differences in body weight, body condition score, body composition, physical examination, food intake, or urinary parameters were observed among groups. Hematological and serum biochemical parameters were within reference ranges and were largely similar among groups. Levels of chloride, cholesterol, and homocysteine were significantly lower at some time points in dogs fed the test ingredient foods compared with the control food, but all remained within reference ranges. Whole blood taurine levels indicated no deficiency. Alanine aminotransferase levels were above the normal range at Day 177 in dogs in the control and 15% test ingredient groups. Fecal score was slightly decreased in dogs fed the 30% or 40% test ingredient foods, and fecal pH was decreased in dogs fed any of the test ingredient foods. Digestibility of most parameters was similar among foods, but apparent fat digestibility was significantly lower in foods with the test ingredient. Overall, these results indicate that the test ingredient is safe for use in dog food.

Introduction: Producing enough protein continues to be a challenge, but alternatives may provide economic and ecological relief. Sufficient testing is necessary to confirm safety and evaluate nutritional value. Our objective was to evaluate the safety, efficacy, gastrointestinal tolerance, and apparent total tract digestibility (ATTD) of brewed chicken protein (BCP; Saccharomyces cerevisiae expressing a chicken protein).Methods: Thirty-two healthy adult dogs (BW = 9.68 ± 1.18 kg; age = 4.16 ± 1.85 yr) were used in a completely randomized design (n = 8/treatment). After a 2-wk acclimation phase, baseline measurements were collected and dogs were allotted to the following treatments and fed for 26 wk: control diet (0% BCP; Control), 15% BCP (Low), 30% BCP (Medium), or 40% BCP (High). Palatability was assessed by comparing dry diets coated with 0% (control) vs. 1% BCP in 20 adult dogs. Data were analyzed using the Mixed Models procedure of SAS 9.4, with p < 0.05 being significant and trends accepted at p < 0.10.Results: Consumption of BCP did not affect food intake, BW, physical parameters, serum chemistry, hematology, and urinalysis. The dry matter, organic matter, and crude protein ATTD were greater (p < 0.05) for High, while the fat ATTD was greater (p < 0.05) for Control. Fecal output was lower (p < 0.0001) and fecal dry matter was lower (p < 0.001) for dogs fed High. Fecal acetate concentrations were lower (p < 0.05) and propionate concentrations tended to be higher (p = 0.06) in dogs fed BCP. Fecal isobutyrate, isovalerate, indole, total phenol and indole, and ammonia concentrations were lower (p < 0.001) and fecal valerate concentrations were higher (p < 0.0001) in dogs fed BCP. Fecal bacterial alpha diversity was lower (p < 0.05) in dogs fed BCP. For beta diversity, dogs fed Control were different than those fed BCP. Over 20 fecal bacterial genera were affected by BCP consumption. Palatability of BCP was high (p < 0.05; 2.93:1 consumption ratio).Conclusion: These results indicate that the BCP ingredient tested is an effective source of protein that is safe for use in adult dog foods at an inclusion level of up to 40%. No detrimental effects were observed, and notable changes to nutrient digestibility and fecal characteristics, metabolites, and microbiota populations suggest potential benefits on gastrointestinal health.