Oral doxycycline pharmacokinetics: Lambs in comparison with sheep

Clearance of Mycoplasma ovipneumoniae in Captive Bighorn Sheep (Ovis canadensis) Following Extended Oral Doxycycline Treatment

Respiratory disease is a significant barrier for bighorn sheep (Ovis canadensis) conservation, and a need remains for management options in both captive and free-ranging populations. We treated Mycoplasma ovipneumoniae infection in six bighorn lambs and five bighorn yearlings at two captive research facilities with twice daily oral doxycycline for 8 wk or longer. Doses of 5 mg/kg twice daily mixed in formula for lambs and 10 mg/kg twice daily mixed in moistened pellets for older lambs and yearlings were tolerated well with minimal side effects. All animals in this case report remain Mycoplasma ovipneumoniae free over 2 yr later. Further evaluation is warranted to confirm efficacy of this therapeutic approach.

Investigation of the Effect of pH on the Adsorption-Desorption of Doxycycline in Feed for Small Ruminants

Orally administered tetracycline antibiotics interact with feed, which may impact their bioavailability and efficacy. Therefore, the pH-dependent adsorption of doxycycline and its interaction with feed for ruminants was studied in vitro. Adsorption experiments on animal feed (135 and 270 mg) with initial doxycycline concentrations of 35, 75, and 150 µg/mL were performed. Desorption experiments were conducted by agitation of a predetermined mass of doxycycline-loaded animal feed in PBS, at pH = 3.0, 6.0, and 7.4, to simulate changes in the gastrointestinal tract. Antibiotic concentrations were determined by LC-MS/MS analysis. The adsorption/desorption of doxycycline was described by mathematical models. Chemisorption with strong intermolecular interactions between the active functional groups of doxycycline and the organic biomass was found. The experimental release curve comprised three sections: initial prolonged 27-30% release (pH = 6.0), followed by moderate 56-59% release (pH = 3.0), and final 63-74% release (pH = 7.4). The sigmoidal model showed a considerable role of diffusion with an initial prevalence of desorption and a decreased desorption rate thereafter. The Weibull equation revealed an initial release stage followed by a lag time section and sustained release. The study of doxycycline adsorption by the animal feed proved a maximum 80% encapsulation efficiency and revealed initial diffusion followed by chemisorption. The highest release efficiency of 74% suggests high bioavailability of doxycycline after oral administration in ruminants.

Comparative Study of the Use of Doxycycline and Oxytetracycline to Treat Anaplasmosis in Fattening Lambs

Lamb icteric carcasses condemnation due to Anaplasma ovis is causing relevant economic losses. A comparative study was developed on the effects of different antibiotics to treat ovine anaplasmosis in fattening lambs. A total of 100 A. ovis naturally infected lambs were selected and randomly divided into four groups of 25 lambs: Group ID, treated with injectable doxycycline; Group OD, oral doxycycline; Group O, injectable oxytetracycline; and Group C, untreated animals for the control group. Clinical, haematological, and molecular analyses were performed before the treatment and 12 and 45 days after the beginning of the treatments, and carcass condemnation was followed after slaughter. The A. ovis bacterial load was high before the treatments in the four groups and decreased significantly 45 days after treatment in the ID and O Groups (p < 0.001). The parameters that were related to haemolysis showed similar results. At the abattoir, 15 out of the 47 examined carcasses were condemned; 7 of C Group, 6 of OD Group, 2 of O Group, and 0 of ID Group. It can be concluded that injectable doxycycline and oxytetracycline significantly reduce A. ovis bacterial load in blood and carcass condemnation at the abattoir. Further studies are needed in order to confirm these encouraging findings.