The performance of lambs for the mating in the autumn in improved native pasture fertilized with 250 kg/ha of mineral formula 5-20-20 was evaluated. Two levels of nitrogen (N) (100 and 200 kg/ha of N as urea) divided in two applications, 70% and 30%, in February, 3, and March, 17, 2005, respectively, were tested in a complete block design with two replications. Plots without N application were used as control. Evaluation was done on continuous variable stocking in order to maintain 16% of forage allowance (16 kg DM/100 kg live weight [LW]). Grazing period extended from January, 21 to May, 31. Studied variables were: stocking rate, DM disappearance, in % of LW, average daily gain, body score condition, weight gain per area and, pregnancy rate. The DM disappearance did not differ between treatments and periods of evaluation, presenting limited values in relation to the probable potential intake. The stocking rate showed positive effect of the level of N and did not differ along the evaluations. The other studied variables (body score condition, average daily gain and weight gain per area) presented significant variations between evaluation periods due to influence of the water deficit that occurred during the experimental period. The pregnancy rate did not show significant effect of the level of N. Despite the water deficit which occurred during the experimental period and compromised the performance of the pasture variables and, by consequence, animal response to nitrogen fertilization, the native pasture improvement by fertilization is capable to support high stocking rates.
average daily weight gain; continuous stocking; forage allowance; live weight gain per area; pregnancy
