We conducted nitrogen balance trials for the project “Brassicas - a win-win option for GHG mitigation and animal productivity” under the SLMACC programme. The purpose of the trials was to determine nitrogen excretions from sheep fed forage rape. The data obtained from the trials contained digestibility measurements. Although various digestibility trials with fresh forages have been conducted, no standard or verified protocol seems to exist. Thus, in addition to analysing our data for nitrogen balance, we also analysed the data in the aspect of how to optimise a digestibility trial with fresh forage. The abstract is the result of this analysis, which can be regarded as a by-product of the project.