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 (p < 0.05) and phytase increased the digestibility of CP and all AA in the diets (p < 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: p < 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: p < 0.001). 5. Pre-caecal gross energy digestibility decreased with RKM inclusion (p < 0.001) and increased with phytase supplementation (p < 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.