Título en español.

Two trials were performed at the Corozal Substation with Holstein heifers subjected to one of five feeding regimes to determine possible effects of feeding practices on development of heifers bred to calve at 28 to 29 months with minimum body weight of 472.5 kg. Pasture supplemented with a bulky feed at either 1.80, 1.35, or 1.35 to 2.70 kg/head/day when pastures were poor did not result in a significant difference in net gains of the animals at 24 mo of age, age at calving, or services per conception when compared to pasture alone. A significant difference was determined in net gains of the heifers in the first trial when consuming 1.8 kg of ground corn/head/day through the duration of the experiment, as compared to other groups in the first trial. The former calved about 2 mo earlier than heifers in other groups. However, the use of any kind of supplement to grazing increases so much the cost of production that if future milk production is not sufficiently increased, which was not measured in those trials, use of the supplement may not be justified. All feeding regimes used in both trials, including grazing alone, showed that heifers can be brought to calving at an average age of 29 to 30 months with an average body weight above 450 kg.