Page 914 - The Veterinary Care of the Horse

Mild inflammation of the peritoneum is not uncommon following castration but it becomes

more serious when infection extends from the scrotal cavity into the abdomen. Signs include
VetBooks.ir depression, pyrexia (the horse has a temperature), colicky signs and inappetance. Treatment
includes antibiotics, non-steroidal anti-inflammatory drugs, fluid therapy and flushing of the

abdominal cavity. The source of infection, e.g. an infected cord is removed. The condition
can be fatal.

Points to remember

Castration will not necessarily eliminate stallion-like behaviour and between 20% and 30%
of horses will continue to behave in this way. Remember that the horse will remain fertile for

a period of at least two weeks after the operation. He should not be turned out with mares for
six weeks.

Finally, it is important to be aware that although this is probably the commonest surgical

procedure performed in the horse, it is relatively major and not without risk.

THE CRYPTORCHID HORSE (RIG)

When a male foal is developing in the mare’s uterus, the testes form in the abdominal cavity

close to the kidneys. In the last month of pregnancy, they normally migrate from the
abdominal cavity down into the scrotum. Occasionally, one or both testicles may fail to

descend or ‘get lost’ en route. This is called cryptorchidism. A cryptorchid horse has one or
both testes retained in the abdomen or the inguinal region. Cryptorchid horses are also known

as ‘rigs’. The condition affects approximately 2–4% of 3–4-year-old colts.
The male hormone testosterone is produced by testicles whether they are in their normal

position in the scrotum or somewhere else inside the horse’s body. This means that rigs
frequently display similar masculine behavioural characteristics to a normal stallion. Rigs

may have a single undescended testicle (unilateral) or both may be retained (bilateral). The
unilateral rig will have one descended testicle in the scrotum and one undescended testicle

which is not visible or palpable from the outside (Figure 19.4). The bilateral rig on the other
hand will have no testicles visible externally with both retained somewhere inside the body.
Approximately 15% of rigs are bilateral.