Question: What is the best way to dehorn a calf? I have a dehorning bolt, but I want to know if I must first cut the horn bud and then cauterise it. What do I do to dehorn a fully grown cow? I have read that if one cuts open the inner tube of a tyre and then tie it tightly around the horn, the horn will eventually fall off.

Calves are usually dehorned using a red-hot standard dehorning bolt when they are between 2 weeks and 2 months old. At this age, cutting off the knob before cauterising is usually not necessary.

Make absolutely sure that the bolt is hot enough. Palpate the area carefully to find the bud before you attach the dehorning bolt to the bud, using a rotating action.

The bolt needs to applied long enough for a clearly visible golden brown ring to appear. This is an indication that the bolt was hot enough and that it was applied for long enough.

The aim of cauterising is to destroy the horn-producing cells at the base of the horn, and in this way stop the horn from growing. It may sometimes be necessary, nonetheless, to first remove a well-developed horn bud with small dehorning shears, after which it is cauterised.

Hoof cutters or even pruning shears can also be used to cut off the small horn bud.

I must mention that chemical cauterisation (using a caustic soda paste) of horn buds is strongly discouraged as it is a source of great irritation to the calf because of the continuous burning sensation. There is also the risk that the chemicals could run down the skin of the head, which will result in chemical burns to the skin.

OLDER CATTLE AND DEHORNING

Calves older than 3 months whose horns have already grown quite a bit, have to be dehorned by a vet. Local anaesthesia should be administered before the horn bud is cut off and the wound cauterised.
Think very carefully before you decide to completely dehorn older, fully grown animals, because of the possible complications that could result. The most important infection is infection of the sinuses, because the sinus cavities are exposed if the horns are removed completely.

Dehorning should preferably be done in winter, when there are fewer flies and maggots around. A vet should do the dehorning as local anaesthesia and good haemorrhage control are essential.

Obviously, good handling facilities and a head clamp are also essential if the procedure is performed. An alternative is to saw off the horn, using embryotomy wire. After the operation the exposed sinuses should then be sealed to avoid complications as far as possible.

The “inner tube method” mentioned would help to cut off the blood supply to the horn for a few days before the procedure described above is carried out. An alternative method would be to cut off only the sharp point of the horn without exposing the sinuses.

The animal’s head musts be held in a neck clamp and the tips of the horns can then simply be cut off, using dehorning shears. This is the procedure used during the processing of feedlot cattle. The aim is simply to remove the sharp tips to prevent injuries.

• This article was written by Prof. Dirk Lourens and appears in Ask the vet: What cattle farmers should know (1), compiled by Dr. Faffa Malan.