Prediction of silage dry matter digestibility from digestible organic matter digestibility

Abstract

Grass silage forms the basal forage for the majority of dairy and beef cattle during the winter indoor feeding period. However its feeding value, as determined by intake potential and digestibility can differ dramatically at farm level as indicated by the Hillsborough Feeding Information System (HFIS). For example, for 7000 silages which were offered to dairy and beef cattle during the 1999/2000 indoor feeding period in Ireland and analysed through the HFIS, dry matter digestibility (DMD) varied from 540 to 830 g/kg DM (Keady, 2000). Many models used to predict feed intake by dairy cattle include a digestibility component (Keady and Mayne, 2000). However some models use DMD whereas others use digestible organic matter digestibility (DOMD). Furthermore commercial laboratories in Ireland measure silage digestibility as DMD while in the UK it is measured as DOMD. To facilitate the use of different models to predict food intake by dairy cattle, often it is necessary to be able to predict DMD from DOMD or vice versa. The present study was undertaken to develop a relationship between DMD and DOMD to facilitate the use of different models for the prediction of food intake when digestibility is available only either as DMD or as DOMD.