Greater feeding value of lucerne silage than lucerne hay has been a common finding of ruminant feeding studies in tropical countries. However, during ensiling, a large proportion of the crude protein (CP) in lucerne is broken down to non protein nitrogen (NPN), (Broderick et al. , 1995). Additives such as formic acid may reduce proteolysis during lucerne ensiling. The objective of the present experiment was to compare the nutrient content, and ruminal and post-ruminal dry (DM) matter and protein disappearance of lucerne silage treated with urea and formic acid.