INFLUENCE OF PROCESSING TREATMENT AND TYPE OF CEREAL ON THE EFFECT OFDIETARY ENZYMES IN BROILER DIETS

One thousand and six hundred 1-day-old sexed broiler chickens (Vedette ; 50% male, 50% female) were randomly allocated to eight treatment gro ups in order to test the effect of the ROXAZYME G enzyme complex (beta -glucanase, xylanase, amylase, pectinase) in pelleted and extruded hig h-energy diets on broiler performance. Two diets were tested. The firs t was a commercial diet based on wheat and com, and in the second 20% wheat was replaced by barley. Both diets were tested in pelleted and e xtruded form with or without enzyme which was added before processing at the level of 0.15 g kg-1. The eight treatments tested were as follo ws: Treatments A and B, pelleted wheat-com diets without and with enzy me respectively; Treatments C and D, extruded wheat-com diets without and with enzyme; Treatments E and F, pelleted barley-wheat-com diets w ithout and with enzyme; Treatments G and H, extruded barley-wheat-com diets without and with enzyme. Energy, fat, N, and fibre utilisation w ere determined with four diets containing barley in the 5th week of gr owth. The enzyme complex significantly improved feed conversion ratio (FCR) (1.81 vs. 1.77; P<0.001) until the end of the growing period (39 days), and liveweight at Day 21 (0.66 kg vs. 0.68 kg; P<0.001). Highl y significant differences were found for liveweight and feed conversio n at Day 39 between diets (20% wheat vs. 20% barley: liveweight, 1.81 kg vs. 1.75 kg; FCR, 1.76 vs. 1.81), and also between processing (pell eting vs. extruding: liveweight, 1.84 kg vs. 1.73 kg; FCR, 1.76 vs. 1. 82). Birds fed on extruded feeds grew slower and utilised feed less ef ficiently than birds fed on pelleted feeds. The extrusion process incr eased the soluble fibre content in the feed, and subsequently the feed extract viscosity was also increased. The interaction between process ing (pelleting vs. extrusion) and grain (wheat vs. barley) for livewei ght at Days 21 and 39 was significant, indicating a greater negative i mpact of extrusion on broiler feed containing barley. In the metabolis m studies a positive trend caused by enzyme supplementation was seen o n energy metabolisability, fat, N, and fibre utilisation, but the diff erences were not significant.