Effect of Fiber Type on Extruded Dog and Cat Foods

To assist weight management, some pet foods are produced with higher fiber content to increase bulking and dilute the energy content of the diet. Miscanthus grass (M) is a novel fibrous ingredient that might have similar functionality to standard fibers used by the pet food industry like cellulose (C), and beet pulp (B). The objective of this study was to determine the effects of dried ground M, relative to C, and B on extrusion processing of dog and cat foods. Both dog and cat diets were made with 10% of each M, C, or B and 90% basal ration. Each diet was split into 3 batches and mixed separately prior to production in a commercial scale single screw extruder (E525, ExtruTech, Sabetha, KS). During production, preconditioner water (PW) and steam (PS), and extruder water (EW) and steam (ES) injections and SME were recorded every 20 minutes. At each time point, 5 kibbles were randomly sampled for diameter and length out of the extruder and, exiting the dryer. From the kibble and die diameters, sectional expansion ratio index (SEI) was calculated (kD²/dD²). Data was analyzed using the GLIMIX procedure of SAS (v. 9.4) and means were separated by significant alpha (5%). For both dog and cat foods, extruder parameters were similar among treatments (cat diets: PW 39.0 kg*h^-1, PS 28.6 kg*h^-1, EW 0 kg*h^-1, ES 18.8 kg*h^-1 SME 96.2 W*kg^-1; dog diets: PW 37.7 kg*h^-1, PS 65.6 kg*h^-1, EW 0.03 kg*h^-1, ES 0.8 kg*h^-1 SME 110.1 W*kg^-1; averages of all treatments). Kibble characteristics (length, diameter, SEI, weight, volume, and density) were similar among all the cat diets. However, dog diets with B had larger (P<0.05) diameter and SEI than M and C. Diets with B tended (P>0.10) to have slightly greater volume than M and greater density than C. These results indicate that M behaved similar to C during extrusion of cat and dog diets and was consistent with the fiber profile between these two ingredients. The small differences that were observed can be adjusted with modest process modifications. In conclusion, the extrusion parameters were not affected by fiber source, and small differences in kibble characteristics can be corrected with modest process adjustments.