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In vitro studies with piglet digesta have shown that intestinal bacteria react depending on intestinal location and supplemented enzyme. Growth inhibition in the small intestine involves lactic acid bacteria (LAB) as the main population. Additionally, in vivo results show that lactate and volatile fatty acids correlated negatively for both enzyme supplemented groups. A shift from lactate to acetate production in the small intestine indicates either a general reduction of LAB or a metabolic change of heterofermentative bacteria switching to acetate production. Furthermore, the growth of a few specific bacterial genera which inhibit other bacteria may also have occured. In a similar study with the mono enzyme preparation and a wheat based diet it was shown that the heterofermentative Lactobacillus reuteri dominated the small intestine of weaned piglets (Zimprich et al., 2001).
The increased growth in the colon can be explained by increasing use of breakdown of NSP- substrates by the enzymes. However, arabinoxylan fragments generated by the monoenzyme were not responsible for the promotion of bacterial growth in the colon, as only the wheat extract showed increased growth in vitro.
Fermentation of available substrates seemed most pronounced in the monoenzyme preparation, however composition of metabolites indicates a different microbiota depending on the nature of the supplemented enzyme.