Translational Animal Science, 2023, 7, txad032 https://doi.org/10.1093/tas/txad032 Advance access publication 21 March 2023 Companion Animal Nutrition Received June 10, 2022 Accepted March 17, 2023. Evaluation of corn-fermented protein as a dietary ingredient in extruded dog and cat diets Spencer C. Smith  and Charles G. Aldrich 1, Department of Grain Science, Kansas State University, Manhattan, KS 66506, USA 1 Corresponding author: aldrich4@ksu.edu ABSTRACT Most pet foods utilize traditional ingredients like corn, wheat, and soy. These ingredients and other grains, such as distillers dried grains (DDG), have been used by the pet food industry. Corn-fermented protein (CFP) is a nutrient-dense enhancement on DDG but has not been evaluated in pet food. Therefore, it was the objective of this study to determine the effect of CFP in the production of extruded pet diets, and to determine the effect on nutrient utilization (digestibility) and stool consistency in dogs, and palatability in dogs and cats. Experimental diets with treatment protein sources (corn gluten meal [CGM], soybean meal [SBM], and CFP) were produced in triplicate using a single-screw extruder. Processing parameters and kibble samples were collected at timed intervals during diet production. Kibbles were evaluated for physical dimension and texture. No differences (P > 0.05) were observed in any physical dimension or texture parameters evaluated, with exception of radial expansion, which was lower (P < 0.05) for CFP kibble compared to others. The CFP kibble required a smaller (P < 0.05) mass restriction valve opening, to keep similar bulk density among dietary treatments. However, there was no difference (P > 0.05) in specifc mechanical energy among treatments during diet production. Twelve beagles were fed the experimental diets in a 3 × 3 replicated Latin Square design in which four dogs were randomly assigned to each of three treatments for each period. Diets were formulated to be isonitrogenous and were supplemented with titanium dioxide to serve as an external marker in order to estimate apparent total tract digestibility. Dogs were housed individually and fed twice daily, and water was available ad libitum. Feces were collected after feedings. The diet produced with CGM was more digestible (P < 0.05) than CFP and SBM for dry matter, organic matter, crude protein, crude fat, and gross energy. Further, the CFP diet was also less (P < 0.05) digestible than the SBM diet for dry matter and organic matter. Dogs fed the diet containing CFP had higher (P < 0.05) fecal mass than those fed SBM and CGM. The CFP diet also resulted in a higher fecal score (P < 0.05) than those fed diets with the CGM diet, but similar (P > 0.05) to the SBM diet. For palatability assessment, dogs had a preference (P < 0.05) for CGM over SBM or CFP, but cats showed a preference (P < 0.05) for SBM and CFP over CGM. Results indicate that CFP is acceptable for use in dog and cat diets. Further research should be conducted to evaluate the use of these ingredients at lower inclusion levels. Key words: corn-fermented protein, digestibility, distillers dried grains, extrusion, palatability, pet food INTRODUCTION The pet food market is rapidly growing and currently contributes approximately 40% to total sales in the pet in- dustry, more than any other factor (APPA, 2021). While there are many new pet food formats being introduced to the market (e.g., freeze-dried, raw, etc.), dry foods consistently dominate the volume (Pet Food Industry, 2021). Humanization has been a major infuence on market trends in the pet food industry. Today’s “pet parents” want their animals to eat as well as they do and are beginning to seek options in ingredient com- position that refect their own purchases (Boya et al., 2015). According to Pet Food Industry magazine (2015), 55% of pet owners are concerned about the amount of “fllers,” such as grains and meat byproducts, in their pet’s diets. However, de- spite these trends, 81% of dog foods and 85% of cat foods still utilize traditional ingredients like corn, wheat, and soy (Packaged Facts, 2016). Use of plant-based ingredients and coproducts may prove economically benefcial in this rapidly growing market (Silva et al., 2016). While less nutrient-dense than animal proteins, it has been found that there is less var- iation in nutritional content between plant proteins rela- tive to animal protein meals (Clapper et al., 2001). Protein concentrates from corn and soy have been used successfully in pet foods for decades. Improvements in processing tech- nology and coproducts from distilling grains from ethanol production have created new variations in these base proteins. Therefore, new alternatives such as corn-fermented protein (CFP) should be considered. Traditional distillers dried grains with solubles (DDGS) have been utilized by the livestock industry for decades due to their high levels of protein, fat, and fber (Lodge et al., 1997; Batal and Dale, 2006). As a coproduct of ethanol pro- duction, the ingredient is readily available and cost-effective (de Godoy et al., 2009). Additionally, the ingredient is very sustainable. The pet food industry has long been practicing sustainability by utilizing coproducts from plant-derived protein sources, such as soybean meal (SBM), or corn gluten meal (CGM; Alonzo, 2017). While these common coproducts have been utilized by the industry for decades, it would be relevant to look for similar alternatives, such as grain coproducts from distillation. CFP is produced using post-fermentation separation technologies to split protein and yeast from fber prior to drying. This process utilizes a series of screens and centrifuges to separate approximately 20% of total DDGS volume into the new high-protein ingre- dient, while the remaining 80% is sold as DDGS. These CFP © The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Downloaded from https://academic.oup.com/tas/article/7/1/txad032/7081667 by guest on 18 June 2023