PSIII-38 Pepsin-pancreatin protein digestibility of various protein sources intended for pet food

Abstract

Abstract Pet food companies need quality protein ingredients to offer new and different options for pet owners. Evaluating these proteins with animal feeding trials are time consuming and expensive. An in vitro (benchtop) method could provide detailed information about protein quality for novel ingredients. Therefore, the objective of this experiment was to develop a pepsin-pancreatin digestibility assay and determine the appropriate incubation time for enzyme hydrolysis to approximate results from animal studies. Ingredients evaluated were faba beans, navy beans, spray-dried granulated egg, chick pea, pea protein concentrate (72% CP and 50% CP), green field peas, and sunflower meal. One gram of test ingredient was mixed with an HCl-pepsin solution and then incubated for 3 or 6 hours at 37°C before NaOH was added, stopping the pepsin reaction. Phosphate buffer with pancreatin was then added and the tubes were incubated for an additional 18 hours. Samples were then centrifuged, washed, filtered, and dried at 105°C overnight. Residual protein was determined with a modified Kjeldahl assay and was used to calculate protein digestibility. Data were analyzed using the GLIMMIX procedure for mixed models (SAS v 9.4, SAS Institute Inc, Cary, NC). There was no interaction between test ingredient and time (P = 0.63). Incubation time did not influence protein digestibility (P = 0.69). Test ingredient did impact protein digestibility. Spray-dried granulated egg, faba bean, green field pea, and pea protein concentrate (50% CP) did not differ with digestibilities above 97% (P < 0.0001). Navy bean had a digestibility of 93%. The lowest digestibilities were sunflower meal and pea protein concentrate (72% CP). Overall, the crude protein digestibility was higher than expected. This data would suggest other factors, such as the amount and activity of the enzyme used, should be altered to obtain digestibility values that are consistent with reported values from animal studies.