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The aim of this study was to evaluate the effects of specific thermal energy (STE) application at the extrusion preconditioning stage on the processing parameters, starch gelatinization, kibble macrostructure, nutrient digestibility, feces characteristics, and palatability of a dog food formulation. Two experiments were conducted, and both used the same dog food recipe. In the first experiment, six amounts of STE were applied by changing steam infusion in the preconditioner to obtain the following discharge mass temperatures: 45°C, 55°C, 65°C, 75°C, 85°C, and 95°C. After evaluating the processing and kibble characteristics, the diets were fed to 36 dogs (six dogs per diet), and nutrient digestibility was determined by total feces collection. Palatability comparisons were carried out with 36 dogs using the two-pan method. Results were analyzed by analysis of variance (ANOVA), and means evaluated by polynomial contrasts according to the STE application (P < 0.05). In the second experiment, three treatments were produced. The extruder was operated with preconditioner mass temperature of 45°C, and the amperage documented. On the sequence, the preconditioner mass temperature was increased to 95°C, and the reduction on amperage was recorded. The extruder feed rate was them increased until a motor amperage equivalent to that of treatment 45°C was observed but keeping constant preconditioner mass temperature at 95°C. Processing and kibble characteristics were evaluated. Results were analyzed by ANOVA with means separated by Tukey's test (P < 0.05). In experiment one, a quadratic reduction of specific mechanical energy (SME) implementation with increasing STE was verified (P = 0.004), with a linear increase in total specific energy application to mass (P < 0.001). Regarding the relationship of starch gelatinization with increasing STE, a quadratic increase after preconditioning and a linear increase in kibbles after drying were verified (P < 0.001). Kibble expansion increased (bulk density, expansion rate, specific length), and hardness decreased with increasing STE (P < 0.001). Apparent nutrient digestibility and food palatability did not change according to STE application. Feces dry matter increased (P = 0.003), but pH and fermentation product content did not change. In experiment two, increasing STE was able to substantially elevate the mass production of the extrusion system while keeping the

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SummaryHairball formation may induce vomiting and intestinal obstruction in predisposed cats. Some insoluble fibres as sugarcane fibre and cellulose can prevent hairball formation. The aim of this study was to evaluate the effect of beet pulp consumption, a moderate soluble and fermentable fibre source, on faecal trichobezoars excretion in adult shorthaired cats fed kibble diets. Eighteen mixed-breed shorthaired cats and three extruded diets were used as follows: a basal diet without added fibre source (PB0-8.8% dietary fibre); BP8-8% inclusion of beet pulp (17.5% of dietary fibre); BP16-16% inclusion of beet pulp (23.8% of dietary fibre). The cats were fed during 31 days and faeces quantitatively collected during three periods of 3 days each (from days 3-5; 15-17; 26-28). Gastrointestinal transit time was determined in the last 3 days of study (from days 29-31). The trichobezoars were separated from faeces, collected, dried and washed in ether for complete removal of all faecal material. The results were submitted to repeated-measure analysis of variance and means evaluated by polynomial contrast (p < 0.05). Beet pulp increased faecal production (p < 0.001) and reduced gastrointestinal transit time (p = 0.003). No alterations were found on trichobezoar faecal excretion, both as considered in number per cat per day of mg per cat per day (p > 0.05). Beet pulp intake did not reduce the number or the size of hairballs eliminated via faeces of shorthaired cats.