Feeding systems costs for rearing beef heifers bred at 18 months of age

Age at first breeding of heifers is related with economic efficiency of cattle production. The determination of feeding systems for rearing heifers is essential to reach high pregnancy rates. The aim of this study was to estimate and evaluate the costs of feeding systems for rearing beef heifers bred at 18 months of age. Feeding systems witch enable a suitable weight gain during each rearing phase were analyzed. Native pasture and supplements were used to compose the feeding systems and to calculate the final cost of each system. Therefore, the following assumptions were defined: weaning weight - 160 kg; weight gain from weaning to breeding - 140 kg; weight at breeding - 300 kg (British breed, 65% of mature body weight). Treatments were determined according to the average daily gain (ADG) in the winter (WIN), spring (SPR) and summer (SUM) period, respectively: LHM - Low (0.000 kg/d), High (1.111 kg/d) e Moderate (0.500 kg/d); MMH - Moderate (0.120 kg/d), Moderate (0.800 kg/d) and High (0.500 kg/d); HLL - High (0.373 kg/d), Low (0.600 kg/d) and Low (0.300 kg/d). HLL reached the lowest cost (R$ 96,19/head), followed by MMH (R$ 114,60/head) and LHM (R$ 134,40/head). The utilization of different feeding systems has economic involvements for rearing females. Heifers bred at 18 months in the autumn need be supplemented at least during one of the three rearing periods. Supplementing heifers to get higher weight gain during the first rearing period (winter) was cheaper than reach higher gains during the second and third periods (spring and summer, respectively).