CHAMPAIGN, Ill. — In a groundbreaking new project, scientists used precision fermentation to produce brewed chicken protein and evaluated it for use in pet food. Dogs that consumed the protein in their kibble during a six-month study had beneficial digestive effects, the researchers found.
Scientists at the University of Illinois Urbana-Champaign and Bond Pet Foods, Inc., in Boulder, Colorado, partnered on the project. The study is believed to be the first to use precision fermentation to produce a protein composed of both yeast and chicken protein and assess its safety in pet food. Precision fermentation has been used for nearly half a century to produce ingredients like enzymes for manufacturing cheese, vanilla and vitamin B12.
Bond’s research and development team began by identifying proteins that were highly abundant in the muscle tissue of chickens and then cross-referencing to their DNA sequence. The DNA was inserted into a specific site in the Saccharomyces cerevisiae (brewer’s yeast) genome to express the chicken protein, which was cultivated in large stainless-steel tanks similar to those used in breweries or other industrial fermentation operations.
After the culture medium was removed, the biomass was harvested, heat treated and spray dried to produce the inactivated S. cerevisiae-containing chicken protein, which was formulated into the dog kibble. Healthy adult dogs that consumed the brewed chicken protein during the six-month feeding study had beneficial changes in their fecal metabolites and gut microbiota, with no allergic reactions or adverse changes in blood chemistry or other markers, said Kelly Swanson, a professor and the director of the Division of Nutritional Sciences at the U. of I.
Photo by Fred Zwicky
The findings, published in the journal Frontiers in Veterinary Science, indicated that the brewed chicken protein was safe and nutritious at proportions of up to 40% of the dogs’ food. Dogs that consumed it showed no differences in body weight, physical condition, blood chemistry or other markers compared with those in the control group.
“It was highly digestible and there were some beneficial changes to the dogs’ gut microbes and metabolites,” said Swanson, who was a corresponding author of the study along with Tomas Belloso, the vice president of regulatory affairs at Bond Pet Foods, which funded the work.
“The main goal was to provide foundational protein for pet health, but it looks like there could be a secondary benefit from the soluble, fermentable fibers in the whole cellproduct for the dogs’ large intestines as well,” Belloso said.
S. cerevisiae yeast products have long been used in commercial pet food, oftentimes serving as palatants — ingredients that enhance the aroma and taste of the food, making it more appetizing for pets. In addition to being a rich source of protein, brewer’s dried yeast also provides complex B vitamins, amino acids and minerals, Swanson said.
Yeast products in pet foods have other positive effects as well, such as elevating concentrations of beneficial fecal bacteria and immunoglobulin A, an antibody in the mucosal secretions of the intestines that plays a crucial role in immune functions by neutralizing pathogens and other substances, Swanson and his colleagues found in prior research.
Dog food containing the brewed chicken protein was tested with a study population of 32 healthy adult dogs. During the two-week acclimation phase, all of the dogs ate a control diet, which was based on chicken by-product meal and brewer’s rice, ingredients often used in commercial dog food. Then the dogs were divided into four dietary groups, three of which were randomly assigned to eat a diet containing 15%, 30% or 40% brewed chicken protein while those in the fourth group remained on the control diet.
All four groups’ diets contained similar levels of organic matter, ash, crude protein and fat, the team wrote. Throughout the study, all four groups were fed amounts intended to maintain their body weight in order to avoid any potential physiological effects that might be associated with weight gain.
The team analyzed blood, fecal and urine samples and monitored the dogs’ food consumption, body weight and condition at four and 26 weeks and found no statistical differences among the dogs in the dietary and control groups. All factors remained within healthy ranges and no detrimental effects were observed throughout the study, Swanson said.
Analyses indicated that inclusion of the brewed chicken protein in the dogs’ diets decreased the digestibility of fats somewhat, although they remained highly digestible overall. The brewed protein also shifted some of the dogs’ fecal metabolites and microbiota. Fecal concentrations of the short-chain fatty acids butyrate, propionate and valerate — which reduce inflammation and have other beneficial effects — rose in proportion to the amount of brewed chicken protein in the dogs’ food, the team found.
While the amount of feces and fecal dry matter produced by the dogs in the three treatment groups decreased in inverse proportion to the amount of brewed chicken protein in their diet, their feces were still soft, moist and of acceptable quality, according to the study.
“When we were formulating these diets, we knew there was a lot of soluble fiber in them, and that was one thing I was a little nervous about — if it would cause loose stools or constipation, which is not a nice outcome for pets or their owners. And I was happy to see that the stool quality was not affected,” Swanson said.
Interest in alternative protein sources for pets and humans has been increasing in recent years. With human and pet populations continuing to grow, so are the needs for sustainable, high-quality sources of protein, Swanson said.
“We’re thrilled to see such positive results from the University of Illinois study. It reinforces the promise of brewed chicken protein as a safe, effective and sustainable option for pet nutrition,” Belloso said.
The paper was co-written by U. of I. animal sciences professor Patricia M. Oba, and alumni Julio Moto and Meredith Smola, who was also the first author. Pernilla Audibert, the co-founder and chief technical operations officer at Bond Pet Foods, also was a co-author.