•Rumen undegradable protein increased during wilting but decreased during ensiling.•Silages had lower true protein concentration than unwilted and wilted herbage.•Acid-treated silage had greater true protein concentration among the silages.•Acid-treated silage had the lowest dry matter losses among the silages. This study evaluated the effects of wilting and ensiling of a lucerne-white clover mixture with or without additives on protein quality and fermentation characteristics. We hypothesized that wilting will increase the rumen undegradable protein (RUP) of a lucerne-white clover mixture and that the use of additives will decrease proteolysis of lucerne-white clover silage. The experimental design was a completely randomized design with three replicates per treatment. Rapid wilting of the lucerne-white clover mixture increased RUP but ensiling of the wilted mixture decreased the true protein content and the RUP concentration. Addition of acid at the time of ensiling was more effective in decreasing proteolysis and preserved sugar compared with the untreated control and inoculant-treated silages, which potentially can improve N utilisation by ruminants.