Information on the castration process for horses

A routine surgical procedure but any surgical intervention has associated risks.

  • Prior To Arranging
  • Preparation Prior To Castration
  • Methods
  • Post-Operative
  • Monitoring Post Operative

Prior To Arranging

  • Spring (March-May) or Autumn (Sept-Nov) is the ideal time (to avoid muddy conditions & flies)
  • Optimum age 6-18 months old

Discussion with your veterinary surgeon may influence your decision regarding the age for castration

Horses should:

  • be examined by a vet prior to a castration visit
  • have two descended testicles
  • be in good health
  • ideally be well handled
  • preferably be vaccinated against tetanus (alternatively, horses will be given an injection of tetanus antitoxin on the day of their castration)

Preparation Prior To Castration

  • Feed as normal the night before but the quantity of overnight hay should be reduced by a third.
  • Please read the practice guidelines on general anaesthesia which can be found here
  • No hard feed the morning of the op but a small amount of hay could be available
  • Drinking water should be available until  one hour prior to surgery
  • A suitable clean, dry, quiet area should be organised (stable, barn or paddock).
  • A clean bucket with warm water
  • A clean patient (if possible!).
  • One or two capable adults available to hold the patient.


There are two methods possible for castrating a horse. Your vet will choose the technique which enables the operation to be carried out in the safest and most efficient way, taking into consideration the size, nature and age of your horse and the facilities available.

Method 1: Sedation plus local anaesthetic
Once sedated, your horse will have an injection of a local anaesthetic injected into their testicles. The testicles are removed whilst the horse is standing up.
This procedure is usually performed indoors and may require a power source for additional lighting.

Method 2: Full general anaesthetic
The horse is given an injection of general anaesthetic which will make them lay down for the procedure. 


  • The horse should be kept quiet on recovery.
  • Careful observation of the patient is advised in the first 8-12 hours post op.
  • Confinement for initial 8-12 hours with a walk-out in hand later the same day (or overnight turnout where appropriate) Exercise should then be encouraged – including lunging/turnout or forced exercise to help prevent swelling within the sheath (ie. 5-10 minutes lunging once or twice daily
  • Rearing / play fighting with other youngsters should be discouraged
  • Hay can be offered post op & a small feed later in the day
  • Most castration sites are left open to encourage drainage
  • Antibiotics & adequate tetanus cover will be administered post op
  • Cleaning of op site is not advisable due to risk of dirt being pushed into the wounds, but gentle hosing is permitted
  • Straw or obvious debris visible from the wounds can be gently removed.
  • An antibiotic spray or powder can be applied onto wounds once or twice daily for 5 days if necessary to prevent fly attraction.
  • After castration the horse should still be kept separate from mares for at least 14 days.

Monitoring Post Operative

  • Post operative dripping of blood can be expected but should normally stop within 20-30 minutes.
  • If bleeding persists or the amount increases, the vet should be called & the patient kept still, in a quiet environment.
  • Sometimes the horse will require further surgery to control the bleeding.
  • Occasional blood-tinged/ light straw-coloured fluid discharging from the wounds is normal and may occur for a few days post op.
  • Swelling at the castration site can also be expected but if it doesn’t resolve, becomes large/firm or more painful the vet should re-examine the horse. Sheath swelling is not uncommon but scrotal swelling should be reported to the practice.
  • If the horse shows any malaise or hind-leg stiffness when walking, please contact the surgery
  • If any tissue appears to be hanging down from the wound (particularly within the first 24 hours after castration) then the vet should be contacted.
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