Study finds brewed chicken protein safe and highly digestible for dogs at up to 40% of diet

A new peer-reviewed study has concluded that brewed chicken protein (BCP), produced through precision fermentation using Saccharomyces cerevisiae engineered to express a chicken protein, is safe for healthy adult dogs when included at levels up to 40% of their diet.

Published in Frontiers in Animal Science, the research was conducted by Meredith A. Smola, Patrícia M. Oba, Julio C. Mioto, and Kelly S. Swanson from the University of Illinois Urbana-Champaign, alongside Pernilla Audibert and Tomas Belloso from Bond Pet Foods, Inc.

The authors say the findings could support the use of precision-fermented proteins as a sustainable alternative to conventional animal ingredients in pet foods.

With global human and pet populations projected to rise sharply, demand for protein is set to increase. The study notes that the pet population already stands at around one billion worldwide, with US dog numbers expected to climb from 85 million to over 100 million by 2030. Producing enough high-quality protein from traditional livestock sources raises environmental concerns, including land degradation, greenhouse gas emissions, and biodiversity loss.

Chicken is among the most widely used proteins in companion animal diets, prized for its palatability and amino acid profile. But, as the authors point out, intensive poultry farming also brings challenges such as waste management, air quality issues, and disease risk. Precision fermentation offers an alternative by producing animal-identical proteins without raising or slaughtering animals, dramatically reducing environmental impacts.

The BCP tested in this study was produced by inserting a codon-optimized DNA sequence for a chicken muscle protein into the genome of S. cerevisiae. The yeast was then fermented under controlled conditions, heat-treated, and spray-dried into a final ingredient containing at least 50% crude protein, with more than 10% of that from chicken protein. The product also contained dietary fiber from the yeast cell walls, including β-glucans and mannanoligosaccharides.

Thirty-two healthy adult beagle dogs were randomly assigned to one of four diets: a control with 0% BCP, or diets with 15%, 30%, or 40% BCP inclusion. All diets were formulated to meet AAFCO nutrient profiles for adult maintenance. Dogs were fed for 26 weeks, with measurements taken for body weight, body condition score, food intake, serum chemistry, hematology, urinalysis, fecal output and quality, nutrient digestibility, and gastrointestinal microbiota.

A separate two-day palatability test with 20 adult dogs compared a standard dry diet coated with 1% BCP against the same diet without BCP.

Over the six-month period, no detrimental effects were observed in any health parameters. Dogs maintained stable body weight and body condition, and there were no consistent changes in serum chemistry, hematology, or urinalysis outside of normal reference ranges.

Minor differences in certain blood measures were recorded at specific time points, such as higher serum IgE concentrations in the high-BCP group at week four, but these were not sustained and showed no signs of allergic reaction.

The authors write: “The lack of change to food intake, body weight, serum chemistry, and hematology over six months of feeding suggests that the inclusion of BCP of up to 40% of the diet for adult dogs is safe” (Smola et al., 2025).

Digestibility trials showed that diets with higher BCP inclusion had greater apparent total tract digestibility (ATTD) of dry matter, organic matter, and crude protein compared to the control diet. Protein digestibility exceeded 80% across all diets.

Conversely, fat digestibility decreased slightly with higher BCP inclusion, a trend the authors note has also been observed in other yeast-based protein studies. They attribute this to the presence of phospholipids, sterols, and soluble fibers in yeast cell walls, which can affect lipid absorption.

Fecal output, both in wet and dry weight, decreased as BCP levels increased, while fecal consistency scores remained within the “acceptable” range of formed, moist stools.

BCP inclusion led to measurable shifts in fecal microbiota composition and fermentation by-products. Dogs on higher BCP diets had lower relative abundances of Fusobacteriota and Proteobacteria – often associated with proteolytic fermentation – and higher levels of Actinobacteriota and Firmicutes, groups linked to fiber fermentation.

The relative abundance of beneficial genera such as Prevotella and Erysipelatoclostridium increased with BCP inclusion, while potential pathogens or proteolytic bacteria such as Clostridium and Fusobacterium decreased.

Fecal metabolite analysis showed lower concentrations of ammonia, indole, and phenol derivatives – compounds associated with protein fermentation and undesirable odors – in BCP diets. Some short-chain fatty acids, notably propionate and valerate, increased at higher BCP levels, which the authors note may indicate beneficial shifts toward saccharolytic fermentation.

In the palatability trial, dogs strongly preferred the BCP-coated diet, consuming it first in 32 out of 40 offerings and showing a nearly 3:1 consumption ratio over the control.

The researchers highlight that brewed proteins like BCP could help reduce reliance on conventional animal agriculture, offering a more predictable supply chain, reduced exposure to disease-related supply disruptions, and significant environmental benefits through lower water, land, and greenhouse gas footprints.

They also note that because BCP production is independent of seasonal and geographical constraints, it allows for precise formulation with consistent nutrient profiles, something that can vary in traditional by-products.

The study concludes that BCP is “an effective source of protein that is safe for use in adult dog foods at an inclusion level of up to 40%” (Smola et al., 2025). The ingredient’s high digestibility, reduced fecal output, and favorable effects on gut microbiota suggest potential additional benefits for gastrointestinal health.

The authors recommend further research to assess its safety and efficacy in dogs and cats at other life stages, as well as to explore any long-term functional benefits linked to the observed microbiome changes.