Baas, T. C. and Thacker, p. A. 1996. Impact of pH on dietary enzyme activity and survivability in swine fed p-glucanase supplenrented diets. can. J. Anim. Sci. i6:24s-2j2. A series oiexperiments was conducted to determine the effect of pH on B-glucanase activity and to monitor the effect of passage through the itomach on the ability of enzymes to degrade B-glucans' In_ exp-1 , B-glucanasl activity was determined in 10 commercially available enzyme products at 5 ,n! levels (2.5, 3 '5, 4.5, 5'5 and 6'5) uiing u discontinuouiassay. Little activity was evident atpH2.5, and activity was only slightly increased at pH 3'5' The highest activ-ity occurred at pH 4.i and 5.5. Enzyme activity declined quickly at pH 6.5. Experiment 2 evaluated the capability of B-glu-.unur. to recover u.tirrity after incubation at subopiimal pH levels. Five enzyme preparations.were incubated at three pH levels (2.5,3.5 and 4.5) for tS, 30, 60 or 120-min. The pU level was then increased to pH 5.5, which was the optimum pH for activity determined in exp. 1 . All enzyme products were ielatively stable at pH 4.5 and 5.5. Enzyme products treated at pH 3.5 started to lose activity and all enzyme iroOucts exhibited a deterioration effeci when incubated at pH 2.5. However, all enz)T nes recovered some activity upon return to pH 5.5. Experiment 3 was designed to evaluate the amount of p-glucanase activity leaving the stomach of t-tre pig. Six barrows cannulated with a simple T-cinnulae located at the start of the duodenum were used in a 6 x 6Latin square deiign experiment. The diets consisted of i control and five diets supplemented with. the same enzymes used in exp.2. The ievel of B--glucanase activity in the digesta from pigs fed any of the diets decreased over time as pH decreased' However, across all products, 52 and26oh of initial activity could siilibe detecied 60 and240 min after feeding. Experiment 4 was conducted to evaluate the effectiveness of the 6ve enzyme sources in improving the performance of pigs fed hulless barley-based diets. Supplementation of hog growing-finishing raiions with any of thi enzyme products failed to significantly (P > 0.05) improve daily gain, f."O intake or feeid"efficieicy. The dlgestibility coefficients for dry matter, crude protein and energy showed a general trend iowards improved digestibility wiih enzym-e supplementation (P > 0.05) with Biofeed producing a significant increase. The overall results oithese experiments indicate itrat atthougtr the low pH found in the stomach of the pig is dehimental to enzyme activity, some enzyme activity is retained in the small intestine of the pig. Therefore, the low gastric pH of the pig and its effects on enzyme activity cannot completely explain the lack of response of pigs to B-glucanase'

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