A comparison of two equine castration techniques

Research output: ThesisDoctoral Thesis

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Abstract

Castration of horses is among the most common surgical procedures undertaken in equine veterinary practice worldwide. It is most frequently performed to reduce masculine behaviour in horses that are not intended or suitable for breeding. Less common indications for castration include testicular disease, including neoplasia, orchitis or trauma, inguinal hernias or torsion of the spermatic cord. Equine castration is traditionally performed with surgical emasculators, and can be undertaken using closed, semi-closed or open techniques in the standing horse after sedation, or in the recumbent animal after induction of general anaesthesia.

Although castration is frequently performed in routine practice, complications of the procedure are common. Post-operative complications range from those that are inconvenient to the owner and cause discomfort to the animal such as swelling and infection, to those that are financially costly and immediately life-threatening such as evisceration or marked haemorrhage. The wide variety of intra and post-operative protocols available to the equine surgeon is testament to the on-going search for ways to improve outcomes with castration. The scientific literature contains conflicting information on outcomes and risk of complications with surgical considerations such as whether to perform castrations using an open or closed technique, in the recumbent or standing horse, with or without primary closure of the skin incision, a certain variation of emasculator or with or without ligation of the vaginal tunic and spermatic cord. Finally, examination of practitioner preferences for equine castration between veterinarians in different regions would be valuable as this information may improve understanding of contemporary castration practices and outcomes.

Recently, the Henderson castration instrument has emerged as another option for castration of horses, and opinions have been divided regarding the efficacy and safety of this method in horses. It is important that the Henderson instrument is subjected to scientific evaluation in a controlled manner for determination of surgical outcomes and comparison with conventional equine castration techniques which rely on emasculation. As such, the aims of the research presented in this thesis were to:

(i) Collect information on the habits, impressions and preferences of Australian equine veterinarians performing castration, their experiences with the Henderson instrument and the rates and types of complications they have experienced when using various methods of castration via a nationally-delivered questionnaire.

(ii) Compare outcomes and complications of castration using a surgical emasculator with the Henderson castrating instrument in a clinical study.

(iii) Observe and report the effects of surgical emasculators and the Henderson instrument on the spermatic cord and internal inguinal ring at the time of surgery.

This is the first study to describe and analyse the castration preferences and outcomes experienced by Australian equine veterinarians (Part 1) and to directly compare castration of horses using the Henderson castrating instrument or emasculators (Parts 2 and 3). Comparison between the two techniques was undertaken using a multifaceted approach that involved determination of clinical outcomes and complications (including those occurring intra-operatively, immediately post-operatively [24 hours] and at longer-term post-operative follow-up [3 months]) in a prospective cohort study (Part 2) and laparoscopic and post-mortem examination of the inguinal and vaginal rings, vaginal tunic and spermatic cord (Part 3).

The results of the questionnaire study found that while there are geographical differences compared to studies performed in North America and the United Kingdom in terms of surgical preferences, the rates and types of complications experienced are consistent with those previously reported in other countries. This information provides insight into the current castration techniques, preferences and outcomes of Australian veterinarians and epidemiological data to further the understanding of associations between particular castration methods and types and rates of complications, which may contribute to moving the industry closer to a gold standard for castration.

The results of the clinical surgical study indicate that the types and rates of complications seen with the Henderson castrating instrument are similar to those with semi-closed castration using the surgical emasculators. Despite this finding, for future investigation of equine castration techniques a larger study involving the Henderson instrument may be warranted as the observational study (Part 3) revealed that in some horses, the Henderson castrating instrument resulted in the tearing of the internal inguinal ring and vaginal ring.

This thesis provides valuable contributions to the epidemiological understanding of equine castration in the Australian context, and has added important knowledge in the form of a prospective study of both the emasculator and Henderson instruments in a prospective cohort study. The observational study should form the impetus to continue investigating the effects of the Henderson instrument on the spermatic cord and inguinal ring in order to develop conclusions about these observed changes that may have implications for horse welfare.
Original languageEnglish
QualificationDoctor of Veterinary Studies
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Hughes, Kris, Principal Supervisor
Award date23 Apr 2020
Place of PublicationAustralia
Publisher
Publication statusPublished - 23 Apr 2020

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