A comparison of the prediction of apparent metabolisable energy content of starchy grains and cereal by-products for poultry from its chemical components, in vitro analysis or near-infrared reflectance spectroscopy

Abstract

Regression models including chemical composition, in vitro digestibility and near infrared reflectance spectroscopy (NIRS) were compared in order to predict the energy value of several feed ingredients for poultry. The nitrogen-corrected apparent metabolisable energy content (AMEn) in cockerels and its proportion on total gross energy (AMEn/GE) were determined in 94 batches from six starchy grains and six cereal byproducts. Two preliminary trials were also designed to adapt in vitro methods for prediction of in vivo energy values for poultry. Mean concentrations of AMEn of the ingredient studied ranged from 2,464 to 3,595 kcal kg -1 DM, and those of AMEn/GE from 53.7 to 80.0%. The most precise model of prediction of AMEn and AMEn/GE values was that based on NIRS equations (R2 cv = 0.823 and 0.861, respectively). The best single chemical predictor of these energy values was the neutral detergent fibre concentration (R2 = 0.616 and 0.736, respectively). Further inclusion of ether extract and ash contents in the AMEn model and those of starch and ether extract in the AMEn/GE model allowed increasing coefficients of determination up to 0.791 and 0.839, respectively. A model including linear and quadratic effects of in vitro organic matter digestibility (IVOMd) provided a similar prediction of AMEn/GE values (R2 = 0.833). However the prediction of AMEn from IVOMd was worse (R2 = 0.62), as variations among batches of GE concentration (from 4,225 to 5,896 kcal kg –1 DM) were little related to in vitro digestibility values.