Amino Acids and Protein Digestibility and Metabolizable Energy Availability of Barley Ration in Response to Grind[R] Enzyme in Broiler Chickens (Report‪)‬

INTRODUCTION Cereals are the major part of a poultry diet and primary sources of feed energy. Balancing the energy to protein ratio is a fundamental principle of feed formulation (Classen and Stevens, 1995). Birds adjust their feed intake to obtain a constant energy intake (Lesson et al., 1996). However, the energy a bird obtains from a cereal is variable and depends on its availability to the bird and the presence or concentration of anti-nutritive compounds such as soluble non- starch polysaccharide (NSP), especially [beta]-glucan in barley. Effect of age of bird on feedstuffs which contain anti-nutrients, such as [beta]-glucan in barley, is important. Decreasing growth rate by barley [beta]-glucan in young chickens could be reduced by fungal or bacterial enzyme in the diet (Campbell and Bedford, 1992). Determination of nutritive values (available energy and protein) of the diet is critical in the poultry industry. Estimation of chemical energy in feedstuff is relatively easy; however, this estimation in birds is not precise and measurement of metabolizable energy is common (Scott et al., 1998). To improve dietary efficiency, it is necessary to elucidate the exact amino acid requirements of poultry (Ishibashi and Yonemochi, 2002). The quality of a feed protein depends not only on nitrogen content, but also on constituent amino acids and their digestibility (Ravindran and Bryden, 1999). Diet formulation based on digestible amino acids will allow the use of alternative protein sources with low digestibility coefficients, because such formulation will improve the precision of least-cost diets and reduce nitrogen excretion from poultry operations (Perttila et al., 2002; Lemme et al., 2004). Although the advantages of the digestible amino acid system are recognized, diet formulation based on the total amino acid content is still widely used in many parts of the world. Because corn and soybean meal, most commonly used in poultry rations, have a high amino acid digestibility, the benefits of switching to the digestible amino acid system would be relatively small. In the future, however, economic reasons will compel the poultry industry to increase the use of an array of cheaper, alternative protein supplements with low digestibility coefficients in feed formulation. In broiler diet formulation, attention should be given to economical and maximum poultry performance (Schutte and Pack, 1995). Therefore, the main objective of the present study was to evaluate the influence of a commercial enzyme (Grind[R]; Danisco, Finland) and site of sampling (excreta and ileum) on estimation of metabolizable energy, protein and, particularly, amino acid digestibility of barley by marker in broiler chickens.