Urea as a substitute for soybean meal in growing lambs fed diets containing buffel grass hay

The aim was examine the effects of substituting the crude protein (CP) from soybean meal (SM) with the CP from urea on the intake, nutrient digestibility and feeding behaviour of feedlot lambs with buffel grass hay as the roughage source. Five uncastrated Dorper × Santa Inês mixed-breed lambs with an average initial weight of 17 ± 1.5 kg were evaluated in a 5 × 5 Latin square design. Treatments consisted of diets in which 0.0, 25.0%, 50.0%, 75.0% and 100% of the CP from SM were substituted by the CP from urea. Compared with diet without urea, dry matter (DM) intake and organic matter intake were similar to diet containing 25% of urea, whereas they were lower in the animals fed diets containing 50%, 75% and 100% of CP from urea. The digestibility coefficients, feeding behaviour, nitrogen (N) balance, N intake and N losses in faeces were not influenced. Urinary N losses differed, with the highest values in the animals fed diets in which 75% and 100% of SM was replaced. Up to 25% of the CP, which corresponds to 3.16% of DM from SM can be substituted by CP from urea in diets containing buffel grass hay for feedlot lambs.