چکیده (انگلیسی):

This review paper is prepared with objective of to revise the available scientific information about the role and source of enzyme supplementation in poultry ration. The biggest single expense in any system of poultry production is feed accounting for up to 70% of total production cost per bird. The poultry industry readily accepts enzymes as a standard dietary component, especially in wheat and barley-based rations. Enzymes are biological catalyst composed of amino acids with vitamins and minerals. They bring about biochemical reactions without themselves undergoing any change. Poultry naturally produce enzymes to aid the digestion of feed nutrients. However, they do not have enzyme to break down fiber completely and need exogenous enzymes in feed to aid digestion. According to the purpose of application, feed enzymes can be fundamentally divided in to enzymes which are to quantitatively supplement endogenous digestive enzymes of mono gastric animals (Proteases, lipases, Amylases) and enzymes which are not produced by mono gastric animals (β-glucanases, Pentosanases and Phytases). Specific degradation site in the molecule, PH value, temperature, and presence of aerators / inhibitorsare some factors affecting the activity of enzyme. Bacteria, fungi and yeast are micro-organisms used as a source of enzyme in poultry ration. Some of the enzymes that have been used over the past several years or have potential for use in the poultry feed industry include cellulase (ß-glucanases), xylanases and associated enzymes, phytases, proteases, lipases, and galactosidases. The benefits of using enzymes in poultry diets include not only enhanced bird performance and feed conversion but also less environmental problems due to reduced output of excreta, including reducing the gut viscosity, increasing the effectiveness of host (endogenous) enzymes, alteration in feed passage rate, effect on excreta characteristics, effect on litter problems, release of nutrients, availability of phosphorus, increase in available energy, and improvement in nutrient digestibility. The degree of improvement obtained by adding enzymes to the diet depends on many factors including the type and amount of cereal in the diet, the level of anti-nutritive factor in the cereal which can vary within a given cereal (for example, low-versus high-ß-glucan barley), the spectrum and concentration of enzymes used, the type of animal (poultry tend to be more responsive to enzyme treatment than pigs), and the age of the animal (young animals tend to respond better to enzymes than older animals), type of gut micro flora present and the physiology of the bird.