Development of a successful spray-dried egg white-based experimental diet for dogs: Effect of heat treatment on diet utilization

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The effect of processing spray-dried egg white (SDEW) was evaluated in two experiments to determine the efficacy of SDEW for use in a semi-purified diet fed to dogs. In previous studies feeding SDEW to growing dogs resulted in poor growth and diarrhea. Therefore to evaluate the possible beneficial effects of heat treating SDEW, four different processing methods were examined: 1) untreated SDEW, 2) extruded SDEW (final product temperature = 105°C), 3) extruded SDEW (final product temperature = 120°C), 4) autoclaved SDEW. Processed SDEW was added to the semi-purified basal diet at 20% of each treatment as the sole source of protein. Diets were fed to ten-weekold Pointer dogs for 14 days which included a 7-day adaptation and 7-day fecal collection period. Dogs fed the untreated SDEW lost weight, while those fed any of the heat-treated SDEWs gained weight. Autoclaved SDEW was more digestible (P<0.05) than untreated or extruded SDEW, although all diets had digestibilities greater than 83%. A protein efficiency ratio (PER) assay was conducted using 8-day-old male chicks to assess protein quality of SDEW. PER values were slightly higher for untreated and autoclaved SDEW than either of the extruded products. Thus, it can be concluded that the weight loss resulting from consumption of untreated SDEW can be prevented by each form of heat treatment evaluated. While autoclaved SDEW had slightly higher digestibility and PER values and lower trypsininhibitor activity than the extruded SDEW, the utilization of the extruded products was still considered adequate. The enhanced utilization of the heat-treated products may have been due to destruction of trypsin-inhibitor during heat processing.