Effects of gastric pH on the activity of exogenous pentosanase and the effect of pentosanase supplementation of the diet on the performance of growing-finishing pigs

Abstract

A series of experiments was conducted to determine the effect of pH on pentosanase activity and to monitor the effect of passage through the stomach of the pig on the ability of enzymes to degrade pentosans. In Experiment 1, pentosanase activity was determined in ten commercially available enzyme products at five pH levels (2.5, 3.5, 4.5, 5.5 and 6.5) using a discontinuous assay. Little activity was evident at pH 2.5, which was only slightly increased at pH 3.5. The highest activity occurred after the pH reached 4.5 or 5.5. Enzyme activity declined rapidly at pH 6.5. Experiment 2 was an in vitro trial designed to mimic the in vivo situation where enzymes would be exposed to a low pH in the stomach followed by a sudden rise in pH when the digesta entered the small intestine. Five enzyme preparations were incubated at three pH levels (2.5, 3.5 and 4.5) for 15, 30, 60 or 120 min. The pH level was then increased to pH 5.5 which was the optimum pH for activity determined in Experiment 1. All enzyme products were relatively stable when incubated at pH 4.5 and then returned to pH 5.5. Enzyme products treated at pH 3.5 only partially recovered activity when returned to pH 5.5 and all enzyme products exhibited a serious deterioration effect when incubated at pH 2.5 and returned to pH 5.5. Experiment 3 was designed to determine the amount of pentosanase activity leaving the stomach of the pig. Five castrates cannulated with a simple T-cannula located at the start of the duodenum were used in a 5 × 5 Latin Square design experiment. The diets consisted of a control diet and four diets supplemented with enzyme. The level of pentosanase activity in the duodenum was relatively stable and, across all products, 84% of initial activity was still present 240 min after feeding. Experiment 4 was conducted to evaluate the effectiveness of four enzyme sources in improving the performance of pigs fed rye-based diets. Performance of pigs fed rye was similar to that of pigs fed a barley-based diet ( P > 0.05). Supplementation with pentosanase generally ( P > 0.05) improved both growth and feed/gain ratios of pigs fed rye-based diets. The overall results of these experiments indicated that passage through the stomach of the pig did not inactivate pentosanase and provided a favorable indication that supplementation of rye-based diets with pentosanase may have the potential to improve pig performance.