Study highlights benefits of extrusion on protein quality in grain-free pet foods

USA – A recent study published in Animal Feed Science and Technology has revealed that thermal screw extrusion significantly enhances the protein quality of grain-free pet foods, whether they include animal- or plant-based protein ingredients. 

The research, conducted by a team from the Department of Animal Sciences at the University of Illinois at Urbana-Champaign, ADM, and Wenger Manufacturing Inc., found that extrusion increases amino acid digestibility without compromising the natural or synthetic taurine content in canine diets.

Traditionally, the pet food industry has relied on animal protein as the primary source of nutrition. However, the diversification of market needs has led to the incorporation of alternative protein sources, including plant proteins. 

These alternative sources have proven to meet pets’ nutritional requirements, as indicated by in vivo digestibility studies.

The study focused on pulses, such as yellow peas, green lentils, and garbanzo beans, which have become popular following the US Food and Drug Administration (FDA) report on dilated cardiomyopathy 2018. 

Although no definitive link has been established between grain-free diets and the condition, the report has spurred further research into these alternative ingredients’ nutrient profiles and digestibility.

The researchers formulated eight grain-free diets to evaluate the impact of extrusion on amino acid digestibility and protein quality. The diets included various combinations of chicken byproduct meal, chicken slurry, yellow pea, green lentil, garbanzo bean, and taurine. 

They used two types of extruders—single-screw and twin-screw—and analyzed diet samples at three stages: raw ingredients, post-preconditioning, and post-extrusion.

The study found that despite the chemically similar diets, those containing yellow peas and green lentils had lower methionine content. However, extrusion did not negatively affect taurine levels in any diet. 

Preconditioning and extrusion significantly improved amino acid digestibility and Digestible Indispensable Amino Acid Score (DIAAS)-like values across most diets.

The results indicate that the heat and mechanical shear involved in extrusion does not degrade amino acids, including taurine, which is crucial given its association with dilated cardiomyopathy. 

The researchers emphasized that grain-free diet formulations could achieve high protein quality in canine diets, with extrusion processing playing a crucial role in enhancing amino acid digestibility.

“The amino acid profiles, including taurine concentration, within the same formula remained constant throughout the processing procedures. This could be an indicator that the heat and mechanical shear from extrusion did not degrade the amino acids, including taurine which has been associated with dilated cardiomyopathy, in the grain-free diets,” the researchers noted.

While the study affirmed that all test diets met the Association of American Feed Control Officials (AAFCO) guidelines, the researchers recommended adding tryptophan and methionine to enhance protein quality further.

The study concludes that thermal screw extrusion is a beneficial process for improving the nutritional quality of grain-free pet foods, ensuring that both animal- and plant-based protein ingredients provide optimal nutrition for pets.

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