This study was carried out to evaluate the effect of recombinant bovine somatotropin (r-bST) administration on profiles of blood metabolites of two different ages Nellore bulls. Sixteen bulls were randomly allotted in a factorial arrangement 2 x 2 (ages: youngs and adults; and r-bST dose: 0 and 500 mg) with four animals per treatment. The mean ages of the young and adult animals were 13.37 and 20.62 months, respectively. Four animals per treatment received saline solution or r-bST 500mg, every 14 days, totaling nine applications per animal during 120 days. The Bulls were fed corn silage and concentrated diet based on corn crumb and soybean meal, twice a day, in individual stalls. Blood was collected every three days for metabolic evaluation. The statistical analyses of the data were performed in three applications, considering three periods (1, 2 and 3). Non-esterified fatty acid (NEFA) concentrations were weekly analyzed. Serum cholesterol, total protein and glucose levels were affected either by period or the treatment (P<0.05). The NEFA was affected by weeks of collection (P<0.05) but not by r-bST treatment (P>0.05).
bulls; growth hormone; r-bST; serum metabolites
