Doxycycline (DXC) is a broad-spectrum antibacterial antimicrobial administered to horses for the treatment of bacterial infections which may also affect donkeys. Donkeys have a different metabolism than horses, leading to differences in the pharmacokinetics of drugs compared to horses. This study aimed to describe the population pharmacokinetics of DXC in donkeys. Five doses of DXC hyclate (10 mg/kg) were administered via a nasogastric tube, q12 h, to eight non-fasted, healthy, adult jennies. Serum, urine, synovial fluid and endometrium were collected for 72 h following the first administration. Doxycycline concentration was measured by competitive enzyme immunoassay. Serum concentrations versus time data were fitted simultaneously using the stochastic approximation expectation-maximization algorithm for nonlinear mixed effects. A one-compartment model with linear elimination and first-order absorption after intragastric administration, best described the available pharmacokinetic data. Final parameter estimates indicate that DXC has a high volume of distribution (108 L/kg) as well as high absorption (10.3 h⁻¹) in donkeys. However, results suggest that oral DXC at 10 mg/kg q12 h in donkeys would not result in a therapeutic concentration in serum, urine, synovial fluid or endometrium by comparison to the minimum inhibitory concentration of common equine pathogens. Further studies are recommended to identify appropriate dosage and dosing intervals of oral DXC in donkeys.

A one‐month‐old Clydesdale colt presented for bilateral scrotal hernia and a patent urachus. Manual reduction of the hernia followed by castration and primary closure of the superficial inguinal rings bilaterally was performed. The umbilical stump was resected along with the apex of the bladder, and the abdomen was closed routinely. During the procedure, the anaesthetist noted difficulty maintaining an appropriate anaesthetic plane. Diagnostics while under general anaesthesia including arterial blood gas evaluation revealed a blood pH of 7.190 and 7.220. In addition, a large mass was noted in the ventral cervical region that was not present prior to surgery. The mass dramatically reduced in size as the endotracheal cuff was deflated. Postoperatively a tracheal rent was identified, and a temporary tracheostomy was performed under endoscopic guidance. The colt was maintained on systemic antimicrobials, NSAIDs and gastric ulcer prophylaxis and was discharged without complication four weeks later.