Administration of Doxycycline Hydrochloride via Drinking Water to Turkeys under Laboratory and Field Conditions

A series of experiments were carried out in order to determine doxycycline hydrochloride (DoxHCl) plasma levels in 6-wk-old turkeys medicated via drinking water containing DoxHCl at a concentration of 250 mg/L under laboratory and field conditions. Maximal plasma concentration (C_max) values of 5.7 (± 1.0) μg/mL and 4.9 (± 1.4) μg/mL obtained after DoxHCl administration during 2 and 7 d, respectively, were not significantly different. A significant difference was found between the area under the plasma concentration-time profile, calculated between 0 and 168 h (AUC(0-168)), C_max, and the minimal plasma concentration (C_min) values obtained after medication with a DoxHCl solution at a concentration of 250 mg/L (431.9 ± 96.6 μg·h/mL, 4.9 ± 1.4 μg/mL and 0.7 ± 0.3 μg/mL) and after medication with a DoxHCl solution at a concentration of 750 mg/L (1,176.5 ± 201.8 μg·h/mL, 12.5 ± 2.7 μg/mL and 2.9 ± 0.4 μg/mL), respectively. The increase in body weight was also significantly higher for turkeys medicated with a DoxHCl solution at a concentration of 750 mg/L (83.7 g/d) than for the lower concentration (35.6 g/d). The DoxHCl solution uptake significantly decreased with the increase of DoxHCl concentration. A C_max value of 1.7 ± 0.6 μg/mL and a C_min value of 0.5 ± 0.1 μg/mL were observed during the field experiment. Water consumption under laboratory conditions was followed for tap water (70 ± 50 mL/kg·d) and for a DoxHCl solution at a concentration of 250 mg/L supplemented with 1 g anhydrous citric acid/L (119 ± 6 mL/kg·d) and revealed to be not significantly different. The variability was significantly higher for tap water than for the DoxHCl solution. The stability of the DoxHCl solution containing 1 g citric acid/L over 24 h was 99% expressed as the percentage of the initial concentration.