When is an enzyme in feed, not a feed enzyme?


Feed enzymes increase the nutritional value of poultry feed, but other kinds of enzymes can be used to improve gut health. Bacterial peptidoglycans negatively affect gut function, these enzymes help break them down, increasing production efficiency.


BY PROF. DR RICHARD DUCATELLE, DEPARTMENT OF PATHOLOGY, BACTERIOLOGY AND POULTRY DISEASES, GHENT UNIVERSITY


T


he practise of adding enzymes to poultry feed is vir- tually an industry standard. Phytases, carbohydras- es, lipases and proteases, as well as increasing the nutritional value of feed, help prevent the negative


effects of anti-nutritional factors in raw materials.


Enzymes for feed Phytases are enzymes that enhance the release of phospho- rus and trace minerals from plant phytate. Carbohydrases, like xylanases, gluconases, furanosidases, degrade non-starch polysaccharides, allow the animals to obtain more energy and/or nutrients from their diet. Proteases and lipases on the other hand, support and reinforce the action of the bird’s own digestive enzymes to break-down protein and fat.


Protection mechanisms in the gut Bacterial cells are protected by several layers including;


membranes, lipopolysaccharides, proteins and peptidogly- cans (PGN). Gram-positive bacteria have a thick outer layer of PGN, whilst gram-negative bacteria have a thinner PGN layer in between the inner and outer membrane that is covered by li- popolysaccharides (Figure 1). In a healthy gut, tight junctions are maintained, and pathogens can’t move through the gut barrier. But in commercial broiler production, damage to the intestine is inevitable. Bacterial cell wall fragments present in the gut, including PGN, can impact nutrient digestion and ab- sorption. This is due to intestinal inflammation reactions PGN may trigger by binding to the epithelial receptor TLR2. Even an- imals in the best of health always have some inflammation in their gut. If it needs to be increased in response to a threat from pathogens, it is easier to do so from that position (e.g. – scouring and vomiting to quickly expel pathogens).


Poultry’s relationship with bacteria All animals are taking in microbes constantly from their food and the environment – the gastrointestinal tract has evolved to cope with this normal threat. The acidic environment of the stomach kills certain bacteria, whilst putting others into a dormant state where they are no longer metabolically active. This means that they can no longer take up nutrients intended for the host animal. They pass to the small intestine, where the nutrients from the feed can be absorbed by the bird. Here the flow of digesta is relatively fast to prevent recovery of the bacteria before they reach the large intestine. Once in the


Figure 1 - PGN is present in the cell walls of both Gram- and Gram+ bacteria. GRAM – Bacteria


GRAM + Bacteria Lipopolysaccaride (LPS) Peptidoglycan (PGN) Porine


Peptidoglycan (PGN) Lipid bilayer Lipoproteins


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▶ GUT HEALTH | DECEMBER 2020


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