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Use of Grain Sorghum as the Primary Grain Ingredient in Premium Extruded Foods Designed for Cats
E. MAICHEL (1), J. Santana dos Reis (2), A. Cavalieri Carciofi (3), S. Alavi (4), A. Brar (1) (1) Kansas State University, Manhattan, KS, U.S.A.; (2) Student, , Brazil; (3) , Department of Veterinary Clinic and Surgery, College of Agrarian and Veterinarian Sciences, São Paulo State University (UNESP), , Brazil; (4) Department of Grain Science, Kansas State University, , U.S.A..

Grain sorghum is rarely used for pet foods due to the lack of scientific data on the nutritional quality and acceptability of sorghum-based products. Some previous studies showed that sorghum could provide nutritional benefits related to slower digestibility of starch or lower glycemic response, which can aid in premium products targeted towards obese, diabetic and geriatric pets.  The aim of this study was to evaluate the effect of particle size on the extrusion of sorghum-based diets for cats. Two types of sorghum (White and Red) milled at three particle sizes (0.5 and 1.0 mm) were incorporated in a premium dog food formulation and compared to a rice-based dog food formulation. Formulas were extruded to achieve processing at two specific thermal energy: specific mechanical energy ratios (STE: SME), using different combinations of screw speed and preconditioning temperature (high STE:SME at 300RPM/ 85-90°C and low STE: SME at 400RPM/75-80°C).  Water and steam flow in the preconditioner was varied to achieve the desired pre-conditioner temperature. The mean in-barrel moisture was 26% (wb). Thermodynamic analysis of the process was conducted to determine the thermal and mechanical energy input and energy losses. Bulk density and hardness of dry expanded cat food increased with particle size. The diets extruded at low STE: SME had higher bulk density and also hardness. Starch gelatinization increased as the particle size decreased. Process conditions did not influence the starch gelatinization. Results indicated that sorghum can be an effective alternative to rice as a carbohydrate source in extruded pet foods.