INVESTIGACIÓN - EVALUACIÓN DE ENSILAJES DE AVENA Y CEBADA EN LA GANANCIA DE PESO DE VAQUILLAS EN CRECIMIENTO (Evaluation of oat and barley silages on weight gain of growing heifers)

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 whole-crop 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) and barley silage harvested at the hard-dough stage, with urea. In each treatment, six dual-purpose 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 ). N o 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