EFFECT OF ENZYME SUPPLEMENTATION ON THE PERFORMANCE AND DIGESTIVE-TRACT SIZE OF BROILER-CHICKENS FED WHEAT-BASED AND BARLEY-BASED DIETS

Three experiments were conducted to study the effects of crude enzyme preparations on the performance and gastrointestinal tract size of chicks fed wheat and barley diets. In the first experiment, enzyme addition (100 and 200 mg/kg of Roxazyme(R) G and 1,000 mg/kg of Avizyme SX) to diets containing Bedford barley improved weight gain (6%) and the feed to gain ratio (5%) over a 6-wk period for both male and female broilers. In Experiment 2, enzyme addition to diets containing Scout (hulless) and Bedford (hulled) barley improved (P less-than-or-equal-to .05) weight gains of Leghorn chicks by 25 and 11% and the feed to gain ratios by 10 and 6%, respectively. Feed consumption increased significantly (16%) only in the case of birds fed enzyme with Scout barley. Corresponding reductions in the relative weights of the crop and gizzards were 15 and 17% for birds fed Scout barley and 7 and 8% for those fed Bedford barley. Enzyme treatment of the diet containing Scout barley also reduced the relative length of the duodenum, jejunum, and ileum and the relative weight of the proventriculus, whereas a similar treatment of Bedford barley resulted in changes in the relative length of the duodenum and jejunum (P < .05). In the final broiler experiment (42 days), crude enzyme addition (100 mg/kg) to wheat and barley diets improved weight gains by 13 and 9% and feed to gain ratios by 7 and 10%, respectively. The addition of enzyme to the barley-based diet reduced the relative weights of the proventriculus (39%), pancreas (24%), liver (8%), duodenum (16%), jejunum (20%), ileum (18%), and colon (29%). Enzyme treatment of the wheat diets did not affect organ size (P > .05). Enzymes improved performance and reduced the size of the gastrointestinal tract, pancreas, and liver in birds fed barley-based diets, whereas a similar treatment of wheat-based diets resulted in less dramatic changes in performance and had no effect on organ size.