the aim of this study was to investigate the integrated effects of native pastures sealing with strategic control of gastrointestinal nematodes on body development of weaned nellore calves, studied between march 1992 and january 1993 in the pantanal region, brazil. two homogeneous groups of weanling calves were put on contiguous paddocks of native pastures with the same physiognomic characteristics and sealed for three and a half months. the paddock where the non-treated group was put, was previously used by cows that were rearing a calf for contamination of the pasture. the treated group remained with low levels of eggs per gram of feces (egf) during the whole experimental period. in the non-treated group, the egf diminished during the assay, ending with similar levels of the treated group. on body development, it was observed a lower body weight loss of the treated group during the dry season and a compensatory weight gain of the nontreated group on the subsequent rainy season. the mean body weight of the two groups was similar at the end of the trial.