Amino acid, energy, phosphorus digestibility and phytate degradation in broiler chickens fed diets containing a meal from dehulled and ethanol-extracted rapeseed

1. This study determined the pre-caecal digestibility of crude protein (CP), amino acids (AA), gross energy, phosphorus (P) and pre-caecal phytate (InsP₆) disappearance of a dehulled and ethanol-extracted rapeseed kernel meal (RKM) without and with exogenous phytase in broiler chickens.2. The experiment utilised a 3 × 2 factorial design with the factors RKM inclusion (0, 12.5 or 25%) and phytase supplementation (0 or 1500 FTU/kg). Diets were fed to Ross 308 broiler chickens from 16 to 21 d of age raised in floor pens (seven per diet).3. The RKM inclusion decreased the digestibility of certain AA (<i>p</i> < 0.05) and phytase increased the digestibility of CP and all AA in the diets (<i>p</i> < 0.05). CP digestibility in RKM, calculated by linear regression, was 75% without and 80% with phytase and Lys digestibility was 81% without and 85% with phytase. There was no significant phytase effect on the slopes of regression lines.4. With increasing RKM inclusion, pre-caecal InsP₆ disappearance decreased without phytase and increased with phytase (RKM × phytase: <i>p</i> < 0.010). Increased RKM inclusion reduced the amount of digestible P without phytase, whereas with phytase, the amount of digestible P increased with RKM inclusion (RKM × phytase: <i>p</i> < 0.001).5. Pre-caecal gross energy digestibility decreased with RKM inclusion (<i>p</i> < 0.001) and increased with phytase supplementation (<i>p</i> < 0.05). Crude protein and AA digestibility of the RKM was high and increased with phytase supplementation. The P from RKM was not digestible without phytase.