THE USE OF ENZYMES TO IMPROVE UTILIZATION OF NUTRIENT IN POULTRY DIETS

Substitution of corn and wheat with barley, rye, triticale and oats has been associated with its variable energy content and detrimental effect on litter quality. The amount of available energy is infl uenced by fi ber content and the amount and composition of cell wall polysaccharides. The predominant Non Starch Polysaccharides (NSP) in barley and oats are the mixed-linked β-glucans, while in rye, wheat and triticale they are the pentosans (arabinixylans). It is now established that the soluble β -1-3, 1-4 D-glucan and soluble arabinoxylan exert antinutritive activity when high concentrations of these cereals are present in broiler diets. Both nonstarch polysaccharides create a viscous environment in the gastrointestinal tract of broiler chickens thereby interfering with the digestion and absorption of nutrients. The increased viscosity of the intestinal contents slow the rate of mixing of digestive enzymes with the substrate and the thickened unstirred water layer at the mucosal surface of the intestine impede the absorption of amino acids and glucose across the microvilous membrane. The ability of dietary fi ber to bind bile acids and the ability of microbiota to deconjugate them can cause bile acid insuffi ciency within the intestine. Whether the formations of β-glucan and arabinoxylan gels in the intestine exert their adverse effect on growth through food intake depression or through impaired effi ciency of digestion is unresolved. Corn alone does not contain soluble NSP in amounts to produce depression of performance Soybean cell walls contain pectic polysaccharides (galacturonans and arabinogalactans), which are half of the NSP. Dietary supplementation of cereal containing diets for broiler chickens with microbial and fungal β-glucanase and pentosanase activity improved feeding value of barley, oats, rye, wheat and triticale resulting in improved growth, feed conversion and reduction in sticky droppings. The improved performance has been attributed to the viscosity reduction and a breakdown of β-glucans and pentosans. Enzyme supplementation of chicken cerals based diets has resulted in improved starch and nitrogen digestability as well as improved absorption of starch, amino acids and lipids. The deleterious effects of β-glucans and pentosans, and the response to dietary β-glucanase or pentosanase are also affected by the age of the chickens.