The Functional Properties and Digestibility of Round and Wrinkled Pea Flour in Swine

Round and wrinkled peas are both a source of starch, but their starches differ in the proportion of amylose and amylopectin. Wrinkled peas have a higher proportion of amylose due to the deficiency of the starch branching enzyme I (SBEI). In contrast, round peas have a lower proportion of amylose and higher total starch content. A higher proportion of amylose content may result in decreased starch digestibility and increase hindgut fermentation, potentially altering the availability of energy. Extrusion is a processing method that causes the starch granule to swell and become gelatinized, thereby altering its structure and digestibility. This thesis evaluated the effect of extrusion and the amylose to amylopectin ratio of round or wrinkled peas on starch digestibility, gut microbial characteristics and glycemic response in pigs. Starch digestibility, short-chain fatty acid content, and microbial diversity was determined in pigs fed round (RPF) or wrinkled pea flour (WPF) that were either unprocessed or extruded using barrows fitted with an ileal cannula, enabling the assessment at both ileal and total tract level. Ileal starch digestibility in pigs fed RPF was increased compared to WPF (P < 0.05). Conversely, pigs fed RPF had the lowest total tract digestibility of starch compared to other three treatments (P < 0.05). There was no effect of extrusion on ileal or total tract digestibility of starch (P > 0.05). There was no effect of treatment on SCFA production in the ileal digesta (P > 0.05). However, regardless of pea type, extrusion resulted in decreased acetic and isobutyric acid concentration in feces, while valeric and hexanoic acid concentrations increased in pigs fed WPF compared to those fed RPF (P < 0.05). The Shannon index, measure of microbial diversity within a sample, revealed that WPF-E fed to pigs decreased microbial diversity compared to those fed RPF-E (P < 0.05) in ileal samples. There was no significant difference in Shannon index among treatments from fecal samples. In the second experiment, glycemic response in response to a bolus of either ground round (RP) or wrinkled peas (WP) that were either unprocessed or extruded indicated extrusion of either RP or WP affected time to peak (TP) and peak height (PH), with pea type having no effect. Extruded peas led to a quicker rise to maximum blood glucose levels following a bolus given to pigs compared to non-extruded peas (48.7 vs 77.8 min; P < 0.05). Additionally, pigs given a bolus of extruded RP or WP had higher concentration of blood glucose compared to non-extruded peas (8.2 vs 7.1 mg/L; P < 0.05). In summary, ileal digestibility in the first experiment indicating RPF with lower amylose content resulted in increased starch digestibility. However, this effect was not observed in the second experiment, where higher glucose release into the bloodstream was expected. This discrepancy may be attributed to a number of factors, including differences in physiological process, feed matrix vs. purified ingredient or the delivery method of starch to the pigs.