The aim of this study was to evaluate the effects of urea as an additive in the ensiling of pearl millet on the intake, feeding behavior, and metabolic parameters of feedlot-finished lambs. Thirty-two uncastrated, mixed-breed male lambs were used in the experiment. Diets were composed of pearl millet silage enriched with 0, 2, 4, or 6% urea plus a concentrate containing ground corn, soybean meal, and a mineral mixture. The treatments did not affect feed intake (P > 0.05) but influenced (P < 0.05) eating time (in min/day, in min/kg of dry matter (DM), and in min/kg of neutral detergent fiber (NDF)) and chewing time in min/kg of DM. Eating efficiency (in g DM/h and in g NDFap/h) responded linearly (P < 0.05) to the increasing urea levels in the silages. By contrast, there was no effect (P > 0.05) of diets on the blood protein profile (total proteins and albumin), although the serum urea levels responded quadratically (P < 0.05). Increasing urea levels in the silage did not change the blood energy profile (cholesterol and triglycerides) or blood enzyme activity (alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT); P > 0.05). In conclusion, the treatment of pearl millet silage with urea does not influence the DM intake or metabolic parameters of lambs, but leads to increased eating time and decreased eating efficiency.
Keywords: Additive; Feed efficiency; Idleness; Rumination; Urea levels.