Effect of different levels of rapeseed meal and sunflower meal and enzyme combination on the performance, digesta viscosity and carcass traits of broiler chickens fed wheat-based diets

The aim of the present experiment was to examine the effect of different levels of rapeseed meal (RSM) and sunflower meal (SFM) and enzyme combination (endoxylanase and beta-glucanase) on the production performance, carcass quality, gizzard development and digesta viscosity of broiler chickens. The experimental design was a 3 x 2 factorial arrangement of treatments evaluating three diet types containing different levels of RSM and SFM (low (L), medium (M) and high (H)) and two levels of enzyme inclusion (0 or 100 g/tonne diet to provide 1220 U xylanase and 152 U beta-glucanase per kg diet). Broiler starter and grower/finisher diets were formulated, based on wheat and soya bean meal and containing 50, 50 and 80 g/kg RSM and 0, 50 and 60 g/kg SFM for L, M and H treatments, respectively, during starter period and 80, 80 and 120 g/kg RSM and 0, 80 and 100 g/kg SFM for L, M and H, respectively, during grower/finisher period, and each diet was fed ad libitum to eight pens of 20 male broilers each. During the starter period (1 to 21 days), birds fed the H treatment had lower (P < 0.05) BW gain (BWG) compared with those fed the L and M treatments. Diet type also influenced (P < 0.05) feed intake (FI). Feeding the H treatment reduced (P < 0.05) FI compared with the M treatment. Diet type and enzyme supplementation had no effect (P > 0.05) on feed conversion ratio (FCR). During the grower/finisher phase (22 to 42 day) and over the entire period (1 to 42 day) birds fed the H treatment had lower (P < 0.05) BWG and higher (P < 0.05) FCR compared with those fed the L and M diets. Enzyme supplementation improved (P < 0.05) FCR compared with the unsupplemented diets. No interactions (P > 0.05) between RSM and SFM inclusion level and enzyme supplementation were observed for any of the measured parameters at any period. Diet type and enzyme supplementation had no effect (P > 0.05) on carcass traits, abdominal fat pad, breast meat yield and jejunal digesta viscosity. Diet type influenced (P = 0.05) relative empty gizzard weight, where the H treatment had higher relative empty gizzard weight compared with the L treatment. Enzyme supplementation tended (P = 0.10) to increase relative empty gizzard weight. The present data suggest that high inclusion of SFM and RSM negatively influenced broiler performance. Enzyme supplementation improved FCR at all levels of RSM and SFM included in this study, but did not recover the reduction in weight gain caused by high inclusion of RSM and SFM.