Extrusion of Peas (Pisum sativum L.): Effects on the Apparent Metabolisable Energy and Ileal Nutrient Digestibility of Broilers

Problem statement: The potential feeding values of grain legumes, such as peas (Pisum sativum), are limited because of the presence of anti-nutritional factors. In particular, protease inhibitors are of interest, but these can be readily destroyed by thermal treatments. In the present study, the influence of extrusion on the chemical composition and nutritive value of peas was evaluated. Approach: Two extrudates were produced by extruding the peas at two moisture levels (19 and 22%) and one temperature (140°C). Four treatment diets consisting of a corn-soy basal diet and three test diets containing raw and the two extruded pea meals were formulated and assayed in digestibility and balance trials using broiler chickens. The test diets were formulated by substituting the raw and extruded pea meals for 25% (w/w) of the basal diet. Ileal nutrient digestibility was calculated using titanium oxide as an indigestible indicator and the apparent metabolisable energy was determined using the classical total excreta collection method. Results: Extrusion had no effect (P>0.05) on the contents of crude protein and starch. Soluble non-starch polysaccharide contents were increased (P<0.05) and the contents of total and insoluble non-starch polysaccharide were lowered (P<0.05) by extrusion. As expected, trypsin inhibitor activity of peas was reduced (P<0.05) following extrusion Extrusion increased (P < 0.05) the apparent ileal starch digestibility, but had no effect (P > 0.05) on the apparent ileal protein digestibility and the apparent metabolisable energy of peas. Conclusion: Under the extrusion conditions employed in the present study, extrusion was not beneficial to improving the nutritive value of peas for broilers.