8:30 am - 9:30 am
4-10C Agriculture/Forestry Centre, University of Alberta, Edmonton AB
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Whitney Van Straten. This seminar is open to the general public to attend.
MSc with Drs. Ruurd Zijlstra and Kate Shoveller.
Thesis Topic: Pulse-based Vegan Dog Food: Examination of Digestibility with or without Added Enzymes in Adult Dogs and Ileal Cannulated Pigs as a Model.
Demand for vegan dog foods is growing, yet little research has been conducted concerning the digestibility of these foods for dogs. The pulses and pulse protein concentrates that provide protein in these foods contain anti-nutritional factors (ANF), which may reduce nutrient digestibility. Addition of exogenous enzymes may help increase the digestibility of these foods, however, due to constraints on companion animal research, studies using dogs alone may not be able to accurately determine enzyme effectiveness.
For the present study two diets were formulated: a low protein diet (L) including mainly field pea and lentil flours, and a high protein diet (H) including mainly field pea and lentil protein concentrates. In chapter 2, ileal cannulated pigs were fed these diets either raw (R), extruded (E), extruded with enzyme added before extrusion (E+P), or enzymes added after extrusion (E+A). The enzyme blend included protease, phytase, cellulase and xylanase. Feces and digesta were collected to determine apparent total tract digestibility (ATTD) and standardized ileal digestibility (SID) of the diets. Extrusion alone increased ATTD of gross energy (GE) by 1% and SID total AA by 4% compared to R (P < 0.05). The addition of the enzyme blend after extrusion increased ATTD of crude protein (CP) and GE by 1%, ATTD of ash by 11-19% (P < 0.05), and increased SID of total AA by 2% (P < 0.05) compared to E. However, the addition of the enzyme blend before extrusion resulted in lower ATTD of organic matter (OM), CP, and GE, and lower SID of AA compared to E (P < 0.05), likely due to overheating during processing.
In chapter 3, dogs were fed the same formulations as controls which were extruded without enzymes (C), extruded with enzyme added before extrusion (P), or enzyme added after extrusion (A). Feces were collected to measure ATTD, fecal metabolites and feces consistency. Unlike for pigs, ATTD of OM, CP, crude fat (EE), GE, or ash did not increase for dogs when enzymes were added after extrusion. However, the addition of enzymes after extrusion did increase concentrations of glucose, xylose, propionic and acetic acids in dog feces compared to C (P < 0.05), indicating the enzymes did hydrolyze some of the insoluble fiber in the diets leading to increased bacterial fermentation. The addition of the enzymes after extrusion also resulted in feces with higher moisture content than for C (P < 0.05), causing loose stools for the dogs. Addition of enzymes prior to extrusion resulted in ATTD of CP lower than C (P < 0.05). Although the ATTD values from pigs were greater than from the dogs, their results followed similar trends and comparison by regression analysis resulted in high R2 values for GE, OM and CP (R2 > 0.7).
In conclusion, extrusion and the addition of enzymes after extrusion increased the digestibility of pulse flour and protein concentrate based diets for growing pigs. The addition of enzymes after extrusion did not increase the digestibility of pulse flour and protein concentrate based diets for adult dogs, but did increase the concentrations of fecal metabolites indicating that the enzymes hydrolyzed some insoluble fiber. However, enzyme addition after extrusion also resulted in loose stools. Addition of enzymes before extrusion resulted in lower digestibility of the diets for both pigs and dogs. Overall, the addition of enzyme after extrusion can be used to increase the digestibility of pulse-based diets for growing pigs, and has some effect on dog intestinal microbiome and feces quality. Comparison of digestibility values from the pigs and dogs resulted in high R2 values, indicating that pigs can be used as a model for dog food digestibility studies.