Farelo de soja em substituição à ureia em dietas para bovinos de corte em crescimento

Abstract

The aim of this trial was to evaluate if non-castrated growing beef steers in feedlot systems would respond to increasing levels of metabolizable protein in the diet estimated by NRC (1996, Level I), through the addition of soybean meal in substitution of urea. Thirty-six steers (24 Nelore and 12 Canchim) with liveweight of 230 kg and 15 months of age were assigned in a completely randomized block design. Diets were formulated according to NRC (1996, Level I) in order to obtain a positive rumen degradable protein balance and sufficient metabolizable energy to ensure an average daily gain (ADG) of 1.3 kg/animal/day in all treatments, which were: urea (U), soybean meal + urea (FSU) and soybean meal (FS). Dry matter intake (DMI) was not affected by treatments (P>0.05). ADG was lower (P<0.05) for U (1.14 kg/animal/day) compared to FSU (1.26 kg/animal/day) and FS (1.28 kg/animal/day). Despite the variation of ADG between predicted by NRC (1996) and actually occurred in this study, it was concluded that it is necessary the inclusion of true protein sources in the diets of growing beef steers.