Prediction of organic matter digestibility of forages in horses using different chemical, biological and physical methods

The organic matter digestibility (OMd) is very important when evaluating the energy value of feedstuffs. Digestibility determinations for a variety of feedstuffs have been extensively carried out by INRA using total faecal collection of in 5–6 gelding trotters (505 kg BW) fed at 1.2 time maintenance for 3 weeks (2 weeks adaptation and 1 week measurements) in order to establish feed tables as well as prediction equations of prediction for routine laboratories. As part of this large study the in vivo OMd of 52 forages were determined. The forages included 7 green natural grassland forages; and 45 hays (39 natural grassland and 7 grasses and 6 legumes). Forages were analysed for their ash; crude protein and cell wall content (crude fibre: CF; NDF; ADF and ADL). The in vivo OMd over of all forages ranged from 41 to 66%.Four prediction methods based on chemical composition; enzymatic degradation; gas production and Near Infrared Spectroscopy (NIRS). Prediction of individual OMd using the NIRS or the enzymatic method were the most accurate (RSD = ±1.8 and ±2.0 respectively. compared with predicting from chemical composition using the CP; NDF and ADL content RSD = ±2.5 or the gas production using faecal inoculums RSD = ±2.5 or ±2.8. The enzymatic method is the easiest for routine analytical laboratories to implement as the transfer of the initial NIRS calibration equations between instruments for routine prediction.