The nutritive value of palm kernel meal measured in vivo and using rumen fluid and enzymatic techniques

Abstract The objectives of this experiment were to determine the in vivo digestibility of solvent extracted and expeller palm kernel meal (PKM) and to establish how well this was predicted by laboratory techniques. Eight samples of expeller PKM and four samples of solvent extracted PKM were collected over 4 years. Their in vivo digestibility was measured by total faecal collection using four wethers per sample. The laboratory methods for predicting digestibility were the in vitro rumen fluid (RF), neutral detergent cellulase with gammanase (NCG), and pepsin cellulase with gammanase (PCG) methods. Gammanase has been added to the latter two methods specifically to improve the prediction of digestibility of PKM. The solvent extracted samples had higher organic matter digestibility (691 vs. 653 g/kg, sed 15.7) and crude protein digestibility (727 vs. 597 g/kg, sed 36.6). However, the expeller samples had higher ( P =0.12) contents of digestible energy (13.4 vs. 12.5 MJ/kg DM, sed 0.48) due to their higher gross energies (20.6 vs. 19.1 MJ/kg DM). None of the laboratory digestibility tests predicted digestibility satisfactorily. The residual standard deviation was 29, 32 and 31 g/kg for the RF, NCG and PCG methods, respectively. In particular, two expeller samples and two solvent extracted samples were grossly underpredicted by the laboratory methods. These results indicate that PKM is a medium quality energy feed for ruminants and that enzymatic procedures including gammanase or the in vitro rumen fluid method do not accurately predict its digestibility.