Arabinofuranosidases appeared to be a revolution in the efficacy of xylanases to break down hemicellulose in plants. They allow to boost the total feed digestibility from energy to protein. To improve the expression of those targeted enzymes, a new method was developed.
Carbohydrates represent the main source of dietary energy in animal feeds. They are essentially provided by cereals or cereal by-products. However, besides starch, the main energy-rich carbohydrate, cereals contain non-starch polysaccharides (NSP), which are not readily digested within the small intestine of birds and pigs due to the absence of the required enzyme activities and thus interfere with feed digestibility and intestinal physiology.
Arabinoxylans, main NSP in cereals
NSP are b(a) polymers, present mainly in the cell walls of the endosperm but also in the bran. They include cellulose, hemicelluloses and pectin and can also be divided according to their nutritional value into water-soluble and water-insoluble fractions (Bach Knudsen, 2014). Soluble NSP are known to possess anti-nutritional properties by either encapsulating nutrients and/or depressing overall nutrient digestibility via modifications within the gastro-intestinal tract. Among the cereals, corn and wheat grains are the mostly used. The cell walls of the outer tissues of the kernel mainly contain cellulose and complex xylans, together with significant amount of lignin. Conversely in the endosperm, cell walls contain almost exclusively arabinoxylans (AX) and b-glucans. Arabinoxylan is composed of a b-(1-4)-linked xylose backbone carrying arabinose residues at the C(O)2 and/or C(O)3 positions of the xylose residues (Figure 1).
The complexity of NSP and their great variety in common feedstuffs used in poultry and swine nutrition demonstrates the need for a large range of enzyme activities in order to alleviate most of their anti-nutritional effects and to get the full availability of their nutrient contents. The higher substitution of corn arabinoxylans further requires those combinations to get full access to the xylose backbone. To have an efficient action in vivo, a large spectrum of different xylanases is required to function all along the digestive tract as well a range of arabinofuranosidases to be able to efficiently break down the most common feedstuff: corn.
References are available on request.
Source: All About Feed magazine, Volume 24.1 (2016)