This work evaluatedthe reproductive performance of first-calf cows at three years of age, submittedor not to protein supplementation at yearling on natural pastures. After calving,cows were managed on natural or improved pastures. The feeding managements werethe following: on natural pastures as yearlings and during pregnancy, post-calvingperiod and breeding season; on natural pastures with protein supplement as yearlingsand only natural pasture during pregnancy, post-calving and breeding season;on natural pastures as yearlings and during pregnancy and on improved naturalpastures (Lolium multiflorum L., Trifolium repens cv. Yi and Lotuscorniculatus cv. São Gabriel) during the post-calving period andbreeding season; on natural pastures with protein supplement at yearling, onnatural pastures during pregnancy, and on improved natural pasture during post-calvingperiod and breeding season. Cows did not differ on body weight, but from calvingto the beginning of breeding season, cows on improved natural pastures presentedhigher weight gain than those on natural pastures (0.203 vs. 0.109 kg/day).Cows in post-calving on natural pastures lost 1.0 point of body condition scoreduring mating, determinant of the lowest pregnancy rate and later conceptionin relation to cows on improved natural pasture. Pregnant cows presented higherbody weight (440 vs. 413 kg) and body condition score (4.14 vs. 3.66 points)than open cows at the end of the breeding season.
