Ether extract and acid detergent fibre but not glucosinolates are determinants of the digestible and metabolizable energy of rapeseed meal in growing pigs

Abstract

ABSTRACT This study was conducted to determine the nutritional composition [acid detergent fibre (ADF), neutral detergent fibre (NDF), ether extract (EE) and crude protein (CP)], digestible energy (DE) and metabolizable energy (ME) of rapeseed meals (RSM) differing in glucosinolates (GLS) contents fed to growing pigs. One hundred and thirty-eight crossbred barrows with initial body weight (BW) of 39.0 ± 1.9 kg were allotted to 1 of 23 diets. Results showed that the content of GLS in RSM ranged from 1.72 to 62.94 mol/g DM with a coefficient of variation (CV) of 89%. The concentration of ADF ranged from 22.78 to 35.71% with a mean of 28.79% [DM (CV = 16.22%)]. The concentration of ether extract (EE) ranged from 1.42% to 14.55% with a mean of 7.78% [DM (CV = 45.16%)]. DE and ME values of the 22 RSM ranged from 10.10 to 15.42 MJ/kg DM and 9.09 to 14.94 MJ/kg DM (P < 0.05). Best-fit prediction equations were as follows: DE (MJ/kg DM) = 8.04 + 0.21 CP (%) + 0.29 EE (%) – 0.18 ADF (%) (R 2 = 0.67) and ME (MJ/kg DM) = 14.82 + 0.23 EE (%) – 0.16 ADF (%) (R 2 = 0.60). The content of GLS was not the key factor affecting DE and ME values of RSM, while EE and ADF are critical to accurately predicting the DE and ME of RSM.