ChileanJAR

The experiment had the objective of evaluating the effect of applying urea on a 4% DM basis, to oat and barley silages, on the productive performance of growing heifers. The treatments were: (A) oat wholecrop silage, harvested at the dough stage; (C) barley whole-crop silage, harvested at the dough stage; (AU) oat silage harvested at the hard–dough stage, with urea; (CU) barley silage harvested at the hard–dough stage, with urea. In each treatment, six dual–purpose Meuse–Rhine–Issel (M.R.I.) heifers (327 kg initial live weight) were used over a period of 64 days. The animals were supplemented with concentrate (1.3 kg animal day^-1). There were differences in the chemical composition of the silages, barley silage having higher energy concentration and lower fiber content. Urea treatments resulted in silages with a higher N content. Ammonia N and pH were higher in treated silages. Soluble carbohydrate content was higher in those silages treated with urea. Treatment C registered the highest (P ≤ 0.05) voluntary consumption (8,5 kg MS day^-1). The lowest consumption was for CU, while the oat silages had similar intermediate values. No differences were observed (P ≥ 0.05) in weight gain among the two oat treatments and the CU treatment. Treatment C had the highest live-weight gains (1.35 kg day^-1) and highest (P ≤ 0.05) feed conversion efficiency (7.2 kg food kg^-1 GPV^-1). No productive benefit was observed in using urea on a 4% DM basis as a preserving agent. The best animal performance was observed in treatment C.