Open standing castration in Thoroughbred racehorses in Hong Kong: Prevalence and severity of complications 30 days post-castration

Abstract

Background: Complications following open standing castration (OSC) in Thoroughbred racehorses are well recognised but variation in their prevalence and severity between populations is not well documented.

Objectives: To describe the prevalence and severity of complications in the 30 days following OSC.

Study design: A retrospective cohort study of veterinary clinical records relating to horses that underwent OSC between July 2007 and July 2012.

Methods: Complications were graded on a severity score from N, no complications, to C3, severe complications. Additional data were accessed for each horse including age, import date, racing history, trainer and veterinarian performing the castration. Bacterial culture and antimicrobial sensitivities were performed on a limited number of castration wounds that became infected.

Results: In total, 250 horses were castrated in Hong Kong using the OSC technique over the period of the study. Sixty percent (150/250) of horses experienced some type of post-castration complication, with eight horses experiencing a severe (C3) complication requiring intensive veterinary treatment. Scrotal swelling, funiculitis and seroma formation were present in 70.0%, 36.7% and 24.7% of cases respectively. Most horses experiencing complications required wound reopening (87.3%; 131/150), and/or an extended course of first-line antimicrobials and/or nonsteroidal anti-inflammatory drugs (75/150; 50.0%). Eight horses had cultures submitted for bacterial sensitivity, with 17 bacterial isolates grown. In vitro, the bacteria cultured were sensitive to enrofloxacin (76%; 13/17) and ceftiofur (100%; 17/17). Resistance was detected to penicillin, gentamicin, oxytetracycline, metronidazole and trimethoprim-sulfadiazine.

Main limitations: Differences in post-castration management cannot be accounted for in this study.

Conclusions: Complications following OSC in horses in Hong Kong were common. The majority were mild and were successfully treated using antimicrobials and simple wound management. Given the high rate of complications and antimicrobial usage identified in this study, a review of the technique is warranted.

Keywords: antimicrobial resistance; castration complication; horse; open standing castration.