Date of this Version
Two trials were conducted to evaluate the 1996 Beef NRC computer model for protein and phosphorus requirements of feedlot cattle. The control ration was formulated for the same levels of crude protein (13.5%) and phosphorus (0.35%) in both trials; however, supplemental protein was from urea in Trial 1 and urea, feather meal and blood meal in Trial 2. The balanced ration was formulated utilizing the 1996 NRC. The balanced ration was changed to effectively meet the changing requirements for DIP, UIP and P. In Trial 1, gains and efficiencies were similar between treatments; however, DMI was lower with cattle fed the balanced ration. In Trial 2, animal performance was unaffected by dietary treatment. These results indicate that the 1996 NRC model does not under-predict finishing steer protein and P requirements.