Interpretive Summary: Evaluation of Torula yeast as a protein source in extruded feline diets

By: Dalton A Holt, Charles G Aldrich

In 2021, US$50 billion was spent on pet food and pet treats in the United States alone. Pet diets are largely sourced from animal proteins; however, the sustainability of these diets remains a major concern. Microbial proteins from microorganisms such as yeasts offer a sustainable protein alternative. Torula yeast (TY) is produced specifically for nutritional value and is grown on low-value woody waste materials. In this work, a commercially available TY product was evaluated in extruded feline diets and compared against soybean meal (SM), pea protein (PP), and chicken meal (CM). During diet manufacturing, the TY ingredient facilitated processing and forming of the final product. When comparing preference of dietary treatments, the diet containing the TY was preferred over that of the PP diet and the CM diet but was not different from the SM diet. Nutrient digestibility was similar or greater for TY compared with other protein ingredients, apart from a lower fat digestibility. Cats fed TY produced softer and less formed feces likely attributed to fiber composition. It was concluded here that TY could be safely included into feline diets, but inclusion level may be limited by fecal quality considerations.