Substituição parcial do farelo de soja por ureia ou amireia na alimentação de cabras em lactação

Thirty-three dairy goats were used to evaluate the effects of partial replacement of soybean meal by urea or starea (urea + extruded corn) on milk production and composition and plasma glucose, urea nitrogen and non-esterified fatty acids concentrations. The animals were distributed in a randomized complete block design, with three experimental diets and eleven replicates. All the experimental diets were isonitrogenous, composed by 40% corn silage and 60% concentrate, with different nitrogenous sources (soybean meal, soybean meal + 2.8% starea or soybean meal + 1.5% urea). The nitrogenous sources used in the diets did not influence dry matter intake, milk production, milk production corrected for 3.5% fat-corrected milk, neither milk fat and protein contents. Plasma glucose and non-esterified fatty acids concentrations were not modified by nitrogen sources. However, plasma urea nitrogen concentration in the harvest after the fourth experimental week was lower for animals fed soybean meal diet. Plasma concentration of glucose, urea nitrogen and non-esterified fatty acids were similar among non-protein nitrogen sources, regardless to the way it was used. Urea used in the extruded form (starea) has no advantage compared to the urea used in the conventional form.