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Several non starch polysaccharide (NSP) degrading enzymes were studied for their suitability as feed enzymes in combination with soya bean meal (SBM) in broiler nutrition. In vitro experiments with SBM and several enzymes isolated from an Aspergillus aculeatus multi enzyme preparation or respective enzyme specificities showed that only enzymes of the 1,4-β-arabinogalactanase type led to effective solublisation of dry matter from SBM, while other enzymes needed very high concentrations to invoke this effect. 1,4-β-galactomannanase activity also showed a high rate of sugar release from SBM, but the release of sugars from treated SBM (simulated stomach digestion with pepsin) was reduced, while an 1,4-β-arabinogalactanase from Humicola insolens still led to a high release of sugars on the same substrate. Synergistic effects on the release of sugars were observed when both galactanase and galactomannanase enzymes were used. Synergistic effects of galactanase and mannanase were also noted for two different endopolygalacturonases, partly purified from the multi enzyme preparation.
In feeding trials with broilers increasing concentrations of the multi enzyme preparation with numerous NSP degrading enzymes showed beneficial effects on feed intake, but high in feed concentrations were needed. Further feeding trials with the galactanase preparation from H. insolens alone and in combination with a mannanase preparation (Gammanase) were conducted. However, due to weak in vivo stability of the galactanase only a small effect on feed conversion was noticed. Additional supplementation of the mannanase drastically reduced live weight gain and feed intake.
It is concluded that enzymes of the 1,4-β-arabinogalactanase type are the most likely candidates for a SBM specific feed enzyme in broiler nutrition, possibly in combination with endopolygalacturonases. However, while a partial degradation of soya NSP may enhance nutrient availability, a high degree of hydrolysis may produce oligo- and monomers with antinutritive effects such as osmotic pressure or microbial fermentation in the small intestine.