The ability of faecal nitrogen to predict digestibility for goats and sheep fed with tropical herbage

Faecal indices were evaluated to assess organic matter digestibility (OMD) for small ruminants fed with Digitaria decumbens. A continuous digestibility trial was conducted with five Creole bucks and five Black-belly rams, fed with fresh cut Digitaria decumbens from 15 to 70 days of re-growth. The amount of herbage offered, the refusals and the faeces were weighed daily for each animal during 55 days. Herbage and faeces samples were kept to determine dry and organic matter (DM and OM), crude protein (CP), neutral and acid detergent fibre (NDF and ADF) and lignin contents (ADL). OMD was calculated per week and per animal. Predictive regressions of OMD were calculated for each species, from all the faecal components measured (CPf, NDFf, ADFf and ADLf), using linear or curvilinear models. Regressions from CPf had the lowest residual standard error (