Effect of Extrusion of Corn on Nutrient Digestibility, Metabolizable Energy, and Performance in Poultry under Tropical Environment

Two experiments were conducted to determine the effect of extrusion of corn on nutrient digestibility, metabolizable energy and performance in poultry under tropical environment. In experiment 1, twenty one male broilers were allotted in an individual metabolic cage and fed mash diets with: 1) basal diet containing 45.7% dextrose; 2) 40% substitution of normal corn for dextrose and 3) 40% substitution of extruded corn for dextrose. There was no difference in GE and N digestibility, however, significant decrease in ME was observed in chicks fed extruded corn diet. In experiment 2, a total of 1,600 broilers were used in a 42-days growth assay. There were 50 chicks per pen and 8 pens per treatment. Treatments were arranged in a 2x2 factorial arrangement with the main effect of feed form and corn type. Treatments were: 1) normal corn mash 2) normal corn pellet 3) +25% extruded corn pellet and 4) +25% extruded corn mash. Chicks fed pelleted feed, regardless of normal or extruded corn, had greater BW of 8.8% (P<0.001) and better feed conversion of 3.8% (P<0.001) than those fed mash feed diet. There was an interaction between feed form and corn type (P<0.01) in feed conversion with the improvement of 6.2% in chicks fed extruded pelleted diet compared to those fed normal pelleted diet. Extruded corn mash decreased the growth performance. These results suggested optimum growth rate and feed conversion in the extruded corn diet may be overcome by steam pelleting. Introduction Corn is the most important feed ingredient of dietary energy. The nutritional improvement of corn is of interested by animal producers. Extrusion process might be the method to improve digestible quality of corn such as enzyme susceptibility, resulting in improvement of energy utilization. A.F.E. Van Der Poel et al (1989 and 1990) determined starch availability in extruded corn compared to infrared corn and showed that in vitro starch availability, ileal digestibility coefficient of dry matter and nitrogen-free extract in young pigs were higher for extruded corn compared to infrared corn. In addition, Herkelman et al (1990) suggested extruded corn improved energy utilization in nursery pigs. While several researchers (A.F.E. Van Der Poel et al., 1989 and 1990 and Herkelman et al., 1990) have studied the effect of feed extrusion in young pig, little research has been done in poultry, especially under tropical conditions, such as in Thailand. The purpose of this study was, therefore, to determine the effect of extrusion of corn on metabolizable energy and nutrient digestibility in poultry (Experiment 1) and the effect of extruded corn and feed form on the growth performance in poultry raised under tropical environment (Experiment 2). Materials and Methods Extruded corn was manufactured through a single screw extruder5 with the length of a barrel of 0.81 m, 24 die openings and the die diameter of 6 mm. Extruded corn was reground through a 125 horsepower hammer mill equipped with 1.7 mm screen and used in experiment 1 and 2. Samples were taken and analyzed for proximate analysis and enzyme susceptibility. 5 Model PHG 135, Wuhan Machinery, china