Efeitos da ordem de utilizaçao de pastagens nativas melhoradas no desenvolvimento e comportamento reprodutivo de novilhas de corte

The experiment was carried out to evaluate the effiect of grazing order, first grazers (TA) and last grazers (T13) in improved pastures (Lolium multiflorum L. and Trifolium vesiculosum Savi cv Yuchi) during the first and second winter/spring seasons post-weaning (W/S- I and W/S-2, respectively) on the growth and the reproductive performance of 62 crossbred beef heifers, from weaning to the first mating. The animals were randomly allotted to TA and TB, by initial weight, in light (L), medium (M) and heavy (H) groups and in taurus or indicus crosses. The TA had higher liveweight gain during W/S-I (.492 vs. .264 kg/day) and W/ S-2 (.674 vs .582 kg/day) than TB. During the summer/autumn period on natural pasture, TA maintained the higher liveweight, but TB had higher liveweight gain (.272 vs .220 kg/day) than TA. Evaluations of reproductive traits scores (RTS) at the beginning of natural mating season were higher in TA than TB. The RTS values for TA zebu heifers were higher than TB zebu, showing less sexual maturity for these females at the beginning of mating season. TA heifers had higher liveweight at the beginning and end of mating season than TB (324.9 vs. 297.0 kg), without differences at pregnancy rate (87.1 vs. 83.9 percent). (RA)