Performance and metabolic pattern of feedlot lambs using soyabean hulls associated to different non-protein nitrogen sources

The aim of this study was to evaluate the metabolic profile of the use of soyabean hulls associated with two sources of non-protein nitrogen (NPN) on the finishing of feedlot lambs. Eighty crossbred Suffolk non-castrated lambs aging 69 +/- 6 days and weighing 23.11 +/- 1.78 kg were used. Lambs were randomly allocated into 4 experimental groups according to the NPN source: conventional urea (1%); protected urea; 1% protected urea + 0.5% conventional urea; and a control group, which did not receive urea supplementation. Blood samples were collected weekly to determine the plasma concentrations of urea, albumine, gamma-glutamiltransferase (GGT), calcium and phosphorus. The control group had higher average daily gain and final weight than protected urea and protected urea + conventional urea groups; however, it did not differ from the conventional urea group. No differences between the groups were observed for dry matter intake, feed conversion or warm carcass yield and carcass finishing. Regarding the serum protein profile, the o group fed conventional urea had higher serum concentration of urea than that of protected + conventional urea. Urea supplementation did not improve the performance of feedlot lambs fed diets with high level of soybean hulls.