Calves performance after the inclusion of slow-release urea in protein supplement for beef cattle

espanolObjetivou-se avaliar a substituicao do farelo de soja (FS) do suplemento proteico por ureia encapsulada (UE; Optigen®) sobre o desempenho de bezerros na epoca seca. Utilizou-se 60 bezerros Nelore, com peso corporal (PC) de 172,37 ± 19,93 kg, mantidos em pastagem de capim-marandu. Os tratamentos foram: 0% UE (100% FS e 0% UE); 25% UE (75% FS e 25% UE); 75% UE (25% FS e 75% UE); 100% UE (0% FS e 100% UE). O delineamento experimental foi o de blocos completos casualizados com tres repeticoes. Nao houve efeito do nivel de substituicao do FS por UE sobre o ganho medio diario (GMD) e PC. O GMD e o PC foram influenciados pelo periodo. Para o GMD o maior valor observado no ultimo periodo (dia 112 a 140) e o menor no segundo periodo (dia 56 a 112). Houve um aumento do PC ate o dia 56, que nao se diferenciou do dia 112 e depois aumentou no dia 140. O consumo de suplemento foi reduzido pela inclusao de UE. Concluiu-se que em pastagens contendo lâmina verde, o FS pode ser substituido por UE sem que ocorra prejuizo ao desempenho produtivo de bezerros na epoca seca. EnglishThe objective was to evaluate the substitution of soybean meal (SM) of the protein supplement for encapsulated urea (UE; Optigen ®) on performance of beef calves during the dry season. Sixty Nellore calves were used, with body weight (BW) of 172.37 ± 19.93 kg, kept under grazing pasture of marandu-grass. The treatments were: 0% UE (100% SM e 0% UE); 25% UE (75% SM e 25% UE); 75% UE (25% SM e 75% UE); 100% UE (0% SM e 100% UE). A randomized blocks design was used with three replicates. There was no effect of the level of substitution of SM by UE on the average daily gain (ADG) and BW. ADG and BW were influenced by the period. For ADG the highest value observed in the last period (days 112-140) and smaller on the second period (day 56-112). There was an increase in BW until day 56, which did not differ from day 112 and then increased on day 140. The supplement intake was reduced by the inclusion of UE. It can be concluded that in pastures containing green leaf, the SM can be replace by UE without adversely affecting the productive performance of calves in the dry season.