Dehorning is removal of the horns after they have formed from the horn bud. Physical methods of dehorning (gouge dehorning) include the use of embryotomy wire, guillotine shears, or dehorning knives, saws, spoons, cups, tubes, or high tension rubber bands. When cattle have large horns they are sometimes “tipped”, a procedure that removes the sharp end of the horn but leaves the base.
Disbudding involves destroying the horn-producing cells (corium) of the horn bud. Horn buds are removed without opening the frontal sinus. Chemical and hot-iron disbudding methods destroy the horn-producing cells, whereas physical methods of disbudding excise them.
Benefits of Dehorning:
- Reduced bruising of carcasses by penmates
- Increased space at the feedbunk
- ease of transport, both through a facililty and during shipping
- decreased trauma by caused by dominant and aggressive animals
- decreased risk of injury to personnel
- increased market value of feedlot cattle
Methods of dehorning
|Hot iron disbudding
(Various hot iron dehorning tools are available, including wood fire heated, LPG heated, butane gas heated and 12- and 24-volt electric)
|-hold calf firmly restrained and the iron heated to a cherry red colour,
-apply the iron firmly over the emerging horn bud.
-Roll the hot iron over the horn bud several times so that a ring of tissue around the bud is burnt through the full thickness of the skin.
-Heat must be transferred evenly all the way around the horn bud to ensure that the horn growth tissue is destroyed. In due course the horn bud will drop off.
-can be carried out anytime
– There is no loss of blood and no wound to become infected.
|-Considered to be very painful
-excess heat applied during hot-iron can damage underlying bone
|Disbudding via cautery
||– is the process of killing the growth ring of the horn using heat.
||-less distress than physical dehorning because nociceptors are destroyed by heat and pain perception is consequently reduced
|-The combination of caustic substances in dehorning paste cauterizes tissue and prevents horn growth. Dehorning paste is applied to the horn buds
– caustic material that chemically burns the cells of the horn bud
-less painful than hot-iron disbudding
-less risk of injury to the calf handler.
|-(e.g., sodium hydroxide, calcium hydroxide) applied to the horn bud can damage surrounding skin and/or the eyes if runoff occurs; as long as the active chemical is in contact with tissue, damage continues
– do not use in rainy weather
-not permitted in some countries
|Scoop, Gouge or Barnes-Type Dehorner
||-Administer sedation, analgesia and local anaesthetic.
-Close the handles together.
-Place the jaws of the dehorner over the horn bud. The objective is to completely remove a ring of skin surrounding the horn base. Therefore, adjust the opening as needed.
-Press the gouger gently against the head. Maintain the pressure and quickly spread the handles apart to bring the blades together to remove skin and the horn bud.
-Control bleeding by pulling the artery with forceps or using a hot iron to cauterize the artery.
-Clean and disinfect the jaws of the gouger between calves.
|– useful after the horn bud attaches to the skull
|– requires expertise – anaesthesia, sedation, analgesia and technique
– requires control of bleeding – pulling arteries or cautery
|Physical removal of buds using knives, shears
||-A curved knife similar to a farrier’s knife (but without a hook on the end) can be used for dehorning.
-Start the cut about 2 cm away from the base of the horn, then draw the knife through the skin towards and through the horn,
-slicing off the horn level with the skull. This will remove an elliptical piece of skin with the horn in the centre.
-If the cut has gone too near the edge of the horn so that the removed horn bud has an incomplete ring of hair, make another small cut to remove the skin to ensure no horn-forming tissue is left from which a scur (a rudimentary, deformed horn) may grow.
-Make the cut swiftly and firmly.
When to dehorn farm animals
Best time to dehorn goats is when the kid is just developing horns. Few days to few weeks of age depending on bred and gender. The kid should be normal – active and nursing normally. Does are slower than intact males to grow horns. Healing will require a couple of weeks
It is best to dehorn calves at less than three months of age. They suffer less stress because they are more easily handled, and the preferred methods cause little or no bleeding, heal quickly, and do not result in any significant setbacks.
Animals should be dehorned on dry cool days to allow the wound to dry quickly with the minimum risk of infection. The best time is late afternoon, when fly activity is usually low. Never dehorn animals in wet weather, because the healing rate is decreased and the risk of infection increased.
Anatomy – where to cut and apply dehorners
For dehorning to be done successfully, operators need a basic knowledge of the internal structure of the horn and how it develops.
As shown in diagram A above, the horn grows from the skin around its base in much the same way as the wall of the hoof grows down from the skin of the coronet of the foot. In young calves up to about two months of age, the horn bud is free-floating in the skin layer above the skull. As the calf grows older, the horn bud attaches to the skull and a small horn starts to grow.
Dehorning should be performed before this attachment to the skull occurs. It then becomes a much simpler exercise, and results in far less bleeding.
To ensure that there will be no regrowth of the horn after dehorning, the operator must remove the horn-forming tissue. This is done by removing a ring of skin at least 1 cm wide with the horn bud (see diagram B above).
The most common mistake when dehorning is to remove an incomplete ring of hair around the horn bud. This allows a scur to grow. Take care to dehorn all calves and to dehorn them carefully and accurately, remembering the ‘1 cm rule’. If the horn bud has an incomplete ring of hair, a second cut will be needed to remove all horn-forming tissue.
Once the horn bud attaches to the skull, the horn core becomes a bony extension of the skull and the hollow centre of the core opens directly into the frontal sinuses of the skull. In this situation, the frontal sinuses are opened and the soft membranous covering of the cranium (skull) is often exposed to view. This is not the brain (as is sometimes thought) and its exposure does not harm the calf. In older calves it takes only a short time after dehorning for this opening to close, but it is during this period that the animal is prone to flystrike and sinus infections.