This work was carried out to evaluate the recombinant bovine somatotropin effect (rBST - BST analogous, commercially obtained by recombinant DNA technique) on average daily gain (ADG), dry matter intake (DMI), organic matter intake (OMI), metabolizable energy intake (MEI) and neutral detergent fiber intake (NDFI), dry matter intake relative to live weight (DMI/LW), feed:gain ratio (F/G), carcass dressing percentage (CDP), dry matter apparent digestibility (DMAD), organic matter apparent digestibility (OMAD), crude protein apparent digestibility (CPAD), crude energy apparent digestibility (CEAD) and neutral detergent fiber apparent digestibility (NDFAD). Twenty-four crossbred heifers (½ Nellore x ½ Red Angus) were used. The heifers were approximately 18 months old and 225 kg of average body weight. All animals were fed with corn silage, citrus pulp and soybean meal during 84 days. 250 mg of rBST were administered subcutaneously by in the ischiorectal fossa. Treatments were: 1) control (administration of 2 mL of saline solution); 2) Single dose and 3) one dose each 14 days. The animals were used in a completely randomized design, with three treatments and eight replicates. The ADG was determined each 14 days. Feed intake and the F/G were determined at the end of the experiment. Apparent digestibility (AD) was determined during seven days using an internal indicator. There was no difference among animals treated or not with rBST for ADG, DMI, CPI, MEI, OMI and NDFI, DMAC and CY. However, the apparent digestibility of DM, OM, CP, CE and NDF was superior in the heifers that received rBST each 14 days.
feedlot; performance; digestibility; heifers; bovine somatotropin
