Castration - Horse

Introduction

Reasons for castration include behavior control, cryptorchidism, tumour removal, severe trauma and sterilisation. It is generally performed between the ages of 12 to 18 months. Surgery should be performed in the early morning to allow for observation throughout the day, and ideally carried out in Spring or Autumn when fly numbers are at a minimum. It should be performed somewhere that is dry and clean with appropriate lighting.

Prior to the sedation or general anaesthetic a full clinical exam should be performed. A scrotal exam should also be carried out to check for the presence of both testicles and any inguinal hernias. Tetanus antitoxin should be given prior to surgery.

Open Castration

Open castration of a horse (Wikimedia Commons)

A technique where tunic is incised and left open. It is simple to perform and allows a 'no-touch' technique to be employed unless a ligature is placed. However there are greater risks of eventration and infection with this method of castration.

This can be performed standing in well mannered colts or stallions with good scrotal development and no history of swelling in the area. The advantages of the standing techniques are that it is quick to perform and it is relatively inexpensive. However it does pose an increased risk to the surgeon and poor access to the surgical site if the horse or pony is less than 14.2 hands.

Alternatively it can be performed in lateral recumbancy. The advantages of this method is the low level of risk to the surgeon. It is also beneficial if the testes are hard to palpate in the standing animal. Disadvantages include cost and the risks of a general anaesthetic coupled with a slow recover time.

Steps:

Check both testicles are present and then sedate or anaesthetise as appropriate.
Clip excessive hair and wrap the tail.
Perform a surgical scrub on the testes.
Infiltrate the testes with local anaesthetic if standing and rescrub the area.
Approach the site from the left hand side of the horse.
Identify the median raphe and push the right testicle up against it.
Make a 1-2cm incision cranial to caudal through the skin, dartos fascia, external spermatic fascia and the vaginal tunic to the right of the median raphe.
Exteriorise the testicle.
Remove the testicle using emasculators:

In the young animal the entire cord can be emasculated in one maneuver but you should ensure there is no haemorrhage before continuing. In the older animal a hole should be made in the mesorchium above the epididymus. Place the emasculator on the caudal portion, incorporating the ductus deferens and the deferens artery and vein for the duration of 30 seconds. Then place the emasculator on the cranial portion and emasculate the testicular artery and vein for at least 90 seconds. Avoid catching any skin in the emasculators and ensure they are applied transversely without tugging on the cord. Remember to position the emasculator nut to nut (meaning that the nut part of the bolt of the emasculator should be on the same side as the testicle, not the body of the horse)! In stallions it is possible to ligate the testicular artery and vein using absorbable sutures to reduce the risk of haemorrhage (however the presence of suture material in the wound clearly increases infection risk).

Inspect the wound for haemorrhage.
Repeat with the second (left) testicle.

Closed Castration

A technique where the tunics are not incised but are instead removed when the cord is transected. It is always performed under general anaesthetic. There is a reduced risk of haemorrhage, eventration and infection when using the closed technique. In addition the wound tends to heal more quickly and the technique provides good visualisation of the testes and minimal risk for the surgeon. However it is slower to perform, therefore increasing the general aneasthetic risks, and it requires good sterility and general anaesthesia.

Steps:

Check both testicles are present and then anaesthetise and place in dorsal recumbancy.
Surgically prepare and scrub the area.
Bluntly dissect the external spermatic fascia to the level of the vaginal tunic (which appears shiny and white).
Break the scrotal ligament and exteriorise the testicle.
Expose and divide the cremaster muscle.
Emasculate the cremaster as proximal as possible. A ligature may be placed if necessary.
Check for evidence of an inguinal hernia.
Twist the testicle and tunic 2-3 times and place transfixing ligatures through the whole cord close to the external inguinal ring.
Emasculate the cord 2cm distal to the transfixing ligature.
Repeat on the second testicle.
Suture the skin if necessary.

Semi-closed Castration

This employs the same technique as open castration except that a transfixing ligature is placed on the vaginal tunic. The benefit of this is that the risk of eventration and infection are reduced, but it is hard to perform in the standing animal, and as it is not sterile it can result in the trapping of infection within the wound.

Laparoscopic Castration

This technique leaves the testes in situ. The benefits of this technique are the low risk of haemorrhage, infection and eventration. Healing and recovery time post-op are also rapid and there is minimal risk to the surgeon. It is also a good technique to use if the testes are hard to palpate prior to surgery. Disadvantages include the high cost of equipment, a longer surgery time, and the need for an HcG stimulation test post operatively to ensure the surgery has been successful.

Post Operative Care

Appropriate observation until recovered if the operation was performed under general anaesthetic
Appropriate antibiotic and anti-inflammatory treatment
In-hand walking for ten minutes three times a day if stabled
A clean, dry and comfortable environment should be provided.
Advise close observation for the following complications: Haemorrhage, eventration, evisceration, excessive oedema, infection and hydrocoele.

Post op oedema is normal in the horse. If it is not excessive advise cold hosing for ten minutes three times a day and continue in-hand walking and anti-inflammatory treatment. It is also normal for the wound to drip a small amount of blood for 3-4 hours post-operatively, however this should not be excessive and there should be no stream of blood.

Also see: Castration Complications - Horse

References

RVC staff (2009) Urogenital system RVC Intergrated BVetMed Course, Royal Veterinary College

Green, P (2001) Castration techniques in the horse In Practice 2001 23: 250-26