THE EFFECTS OF XYLAZINE ON PLASMA-CONCENTRATIONS OF GROWTH-HORMONE, INSULIN-LIKE GROWTH-FACTOR-I, GLUCOSE AND INSULIN IN CALVES

The purpose of the present study was to examine the responses of plasm a growth hormone (GH) and insulin-like growth factor-I (IGF-I) levels to intravenous injection of xylazine in female dairy calves. Xylazine (0.05, 0.15 and 0.30 mg/kg body wt., iv) injections induced a signific ant dose-dependent increase in plasma GH level within 30 min. After pl asma GH levels reached peaks, GH concentrations began to decrease imme diately and they returned to control levels 1 h after xylazine injecti on. Plasma IGF-I concentration tended to be suppressed by xylazine tre atment. Xylazine induced a significant dose-dependent increase in plas ma glucose for 3.5 to 5.5 h after the treatments. Xylazine also induce d a significant decrease in plasma insulin level within 30 min after t reatments. The present data suggested that xylazine stimulates GH rele ase in cattle.