The experiment evaluated the reproductive performance of primiparous beef heifers at two years old ('one year system'). These heifers data were collected at Agropecuaria Guatambu, Dom Pedrito, RS, of 395 beef calves from three genetic groups, Hereford (H); 3/4 Hereford -1/4 Nellore (1/4 N); 5/8 Hereford- 3/8 Nellore (3/8 N). The heifers were submitted to three alternatives autumn-winter feeding systems a) continuous grazing on cultivated annual ryegrass (L. multiflorum Lam) (PAST); b) continuous grazing on natural pasture plus energy and protein supplementation (CNR); c) feedlot, with sorghum silage plus non proteic nitrogen (SIL). After 88 days, the animals of the three alternatives grazed together on improved natural pastures (L.multiflorum; T.repens; L.corniculatus). Liveweight (LW), body condition (BC), pregnancy rate (Pr), calving (C) and weaning rate (W) were recorded. At the end of mating period PAST heifers were heavier and had greater BC than SIL and CNR. The use of different feeding systems did not show significant differences in Pr, C, W. H and 1/4 N primiparous cows were more productive at 'one year system' with greater weaning rates (51.8 and 48.6%; P> 0.05) than 3/8 N (26.4 %; P<0.01).
age at first calving; beef heifers; crossbreeding; production systems
