CONCENTRACIÓN DE UREA EN PLASMA Y RESPUESTA PRODUCTIVA DE CERDOS EN INICIACIÓN ALIMENTADOS CON DIETAS SORGO-PASTA DE SOYA BAJAS EN PROTEÍNA PLASMA UREA CONCENTRATION AND GROWTH PERFORMANCE OF NURSERY PIGS FED SORGHUM-SOYBEAN MEAL, LOW-PROTEIN DIETS

There is little information on the use of low crude protein (CP) diets for nursery pigs. Therefore, two experiments were conducted to determine the minimum percentage of CP in sorghum-soybean meal diets that would not affect growth performance, using plasma urea as a marker. In experiment 1, the treatments (%CP) were: T1) control 20.5; T2) 19.0; T3) 17.5; T4) 16.0; T5 14.5, applied to 10 nursery female pigs using a cross over design with periods of 7 d. The last day of each period, a blood sample was obtained from the cava vein to determine urea. The lowest concentration of this metabolite indicated that the CP in the diet can be reduced by as much as 16%. Using exponential non-linear regression, it was determined that the CP in the diet can be reduced by as much as 14.86% and increased by as much as 20.12% to obtain the minimum and maximum plasma urea concentration. In experiment 2, the treatments (%CP and Mcal EM kg −1 ) were as