The effect of lipase, amylase and protease addition on growth performance and nutrient digestion in young broiler chickens fed

Research has shown that newly hatched birds may be deficient in key digestive enzymes and that the immaturity of the digestive system may result in poor utilization of dietary nutrients. It has also been demonstrated that nutrient digestion rather than the ability to absorb nutrients seems to be the primary limiting factor. Therefore, dietary supplementation of enzymes not produced in sufficient quantities by young chicks (i.e., lipase, amylase, protease) has been investigated in our laboratory. In one study, no effect of lipase addition (100 U/kg diet) on growth performance and fat utilization in broilers (4-18 d) fed a wheat-soybean meal diet was noted. Apparent digestibility of fat averaged 77.6% in the ileum and was the same (77.6%) following lipase addition. Total tract digestibility of fat averaged 88.0% and was similar to that of the lipase supplemented diet (87.8%). A similar study was conducted to determine if amylase and protease addition would improve nutrient digestion during the first two weeks of growth. The corn-soybean meal diet was fed in a mash form. The experimental treatments included the control diet and the diets supplemented with either amylase (10,000 U/kg) and amyloglucosidase (10 U/kg) or amylase, amyloglucosidase and protease (4,000 U/kg). There was no effect of enzyme supplementation on growth performance. Body weight gain and feed efficiency averaged 91.6, 95.5, 97.1g and 1.41, 1.38, 1.38 for the control and the amylase or amylase plus protease supplemented diets, respectively, in week one of the experiment (1-7 d), and 235.9, 242.8, 240.0g and 1.43, 1.40. 141 in week two of the experiment. This was corroborated by similar ileal starch and protein digestibility values which averaged 96.8, 96.8, 96.9% and 83.9, 80.1 and 79.6%, respectively, for the control and the amylase or amylase plus protease supplemented diets. Total tract digestibility of starch averaged 97.8, 97.7, and 97.7% for the three diets and was followed by similar AMEn values of 3129, 3129, and 3106 kcal/kg diet. It could be concluded from this study that the digestive enzyme deficiency in young chickens may not be as pronounced as originally thought. Consequently, supplementation of young poultry diets with starch-, proteinand fat-hydrolyzing enzymes should be reconsidered.