The use of non-protein nitrogen (NPN)
especially urea as the sole or supplemental
source of nitrogen in ruminant rations has been
the subject of extensive research over the last
30 years and many reviews on the subject are
now available (Briggs, 1967; Chalupa, 1968;
Loosli and McDonald, 1968). Its utilization in
conjunction with low quality roughages was
discussed recently in Uganda (FAO, 1971).