Dehorning of dairy calves

Horns are the pairs of hard, bonelike, permanent growths projecting from the heads of cattle. They grow from a unique area of skin cells at the base of the horn. At about two months of age, horns become attached to the frontal bone of the skull. A sinus lies within the skull beneath the horn bud. As the horn grows and attaches to the skull, this frontal sinus joins into the adjacent portion of the horn. 

Horned cattle have horns because they have not been dehorned or they are not polled. Some breeds are naturally (genetically) hornless because they do not grow horns. Dehorning of horned cattle is the process of removal of their horns or the process of preventing their growth. A polled animal is one that grew no horns or one that was dehorned. Disbudding by chemical or hot-iron destroys the horn-producing cells of the horn bud. Surgical disbudding removes the horn bud and the horn-producing cells of the horn bud. Dehorning removes the horn and horn-producing tissue after horns have formed from the bud. 

Advisors commonly recommend dehorning young calves to:

Owners may choose to manage their cattle with or without horns. For beef cattle, the selection will depend on the available handling facilities, the producer's ability, the awareness of dehorning effects, and the market available for the calves. Owners with guaranteed buyers willing to purchase green calves (horns and testicles in place) at the same price as processed calves (castrated and dehorned), might be advised to avoid these procedures. However, this buyer is very rare. Most purchasers of green calves are well aware of the risks associated with processing older calves and routinely bid less at auction. Preconditioned (castrated, dehorned, vaccinated, bunk-adjusted) calves may bring a premium price. Generally, horned cattle are discounted at auction. Breeders of horned Herefords may use methods to train horns to grow in a cosmetically appealing fashion - just like braces on your teeth.

For dairy cattle, naturally polled animals are very rare. Therefore, dehorning is a common management practice on dairy farms. In Ontario, housing systems and milking parlours are designed for dehorned cattle. Organic dairy producers may choose to work with horned cattle. There is a need for housing and feeding equipment designs to accommodate dairy cattle with horns. 

Dehorning requires labour and imparts risks to the animal and the operator. In addition, producers and consumers have concerns about animal welfare implications associated with dehorning techniques. Breeding polled cattle is a non-invasive way to dehorn the cattle population. Polled inheritance is very complex. Nonetheless, the beef industry is making steady progress towards dehorning through genetics. Producers may resist breeding strategies to dehorn because of a belief that the polled gene is associated with impaired productivity. To date, research studies show no difference for several important traits between horned and polled cattle. Within the beef breeds, producers have access to polled genetics. There is scarce availability within the dairy breeds. The industry needs genetic tests to identify horn status and thus, breed polled cattle. Although the gene for polled has not been identified, its position and markers near it are known. Five markers seem to be close enough to provide 90 per cent accuracy of the polled or horned characteristic being inherited by a calf.

A Canadian Expert Committee on Farm Animal Welfare and Behaviour recommends dehorning cattle using genetics as the most welfare friendly technique. The Committee recommends promotion of the use of polled sires within the beef industry in Canada. The use of a naturally polled bull from naturally polled ancestors over horned breeding cows should result in the birth of polled calves. Continuous use of polled bulls over these female offspring should ensure that all calves continue to be polled. This method has obvious advantages where polled breeds are available with production characteristics similar to those of horned cattle. 

Dehorning at a young age minimizes hazards to the calf, the cow-calf producer, and the feedlot owner. Hazards for calves and owners include:

Many producers choose to dehorn new-born calves because:

Although there is no evidence that pain differs between young and older calves, there is less risk with dehorning of young (less than eight weeks) calves.

The cow/calf producer's decision to dehorn and the timing (age) will be influenced by his or her facility, available labour, expertise with the techniques, awareness of the impact of the procedure on calf health and productivity, and market for the calves. The feedlot purchaser is able to selectively purchase horned or dehorned (polled) cattle with price as well as some of the above factors influencing the decision. In general, dairy calves receive intensive care and producers have an opportunity to dehorn their calves at a young age. It is each owner's responsibility to ensure humane and safe completion of the dehorning procedure on the calves entrusted in their care.

The Canadian Veterinary Medical Association (CVMA) recommends that, when dehorning is necessary, it be performed within the first week of life. 

Normal management procedures provide a convenient time for dehorning. At one day of age, insertion of an identification ear tag and injection of the calf with vitamin E-selenium dictates that the calf be restrained. Disbudding could be performed at the same time. Some beef producers prefer to batch the calves up weekly during calving season and dehorn many at one time. Others will catch all calves prior to turning them to grass with their mothers. This may be when calves are six to eight weeks of age and would also be an ideal time to administer the second injection of vitamin E-selenium. Dehorning at an early age (less than eight weeks) reduces the risk of serious infection because the horn bud is removed without opening the sinus (cavity) into the skull. When surgically dehorning older calves, the sinus is opened. On dairy farms, calves may be dehorned by a veterinarian or her assistant during the monthly herd health visit. Avoid the summer and autumn periods when dehorning calves. The risk of infection and fly strike is too great. Dehorn in early spring, late fall and winter only.

On each farm, the timing of dehorning will be based on the management system in operation. Dehorning at a young age should suit most management systems. 

At packing plants, trim from bruised carcasses of animals in groups with horned cattle is twice that of comparable groups of hornless cattle. According to the Canadian Beef Quality Audit, bruising costs the industry $10 million a year. Dehorned cattle may incur fewer financial penalties at sale. 

Livestock owners and veterinarians recognize that some people consider dehorning offensive. Nonetheless, dehorned cattle create a safer workplace for herdmates, handlers and workers - a benefit that outweighs the short period of discomfort at dehorning time.

Choices in anaesthesia and pain relief include:

The cornual nerve supplies sensation to the horn. This nerve travels from immediately behind the eye to the base of the horn. It lies underneath a small overhanging ledge of bone that is a part of the skull. This ledge is easily detected with slight finger pressure. A vein and an artery are found in association with the nerve. Administration of the anaesthetic is simple in young calves. Many veterinarians train their clients in the technique.

One nerve provides feeling to each horn. Blocking the nerve makes dehorning easier on the calf and on the person doing the job. You must block one nerve on each side of the head. Lidocaine anaesthetic is a prescription drug and is only available from your veterinarian. This procedure requires clinical training and practical experience. Local anaesthetic should be given by a veterinarian, a trained veterinary technician, or a trained operator. 

The choices of dehorning techniques range from genetic to surgical. The risks to the calf and the operator vary with each technique. Many producers choose to dehorn new-born calves because the techniques are easier for the operator, less stressful on the calves and they demonstrate concern for the animals' welfare. Here are the common dehorning methods.

Figure 1. marks the location on a bovine skull of the midpoint between the horn base and the outside corner of the eye. Anaesthetic is injected beneath the ridge of bone shown with the X and arrow in the figure.

Horned or polled cows mated to a naturally polled bull (Angus) will give birth to polled calves. However, some non-naturally polled bulls carry the gene for horns and will not breed true for the polled trait.

Caustic chemicals will prevent the growth of horns when properly applied to the horn buds of new-born (less than one to three weeks of age) calves. The chemical destroys the horn-producing cells around the horn bud. The chemicals are available as sticks or pastes (Figure 2). To protect yourself, wear gloves when applying the chemicals. To protect the calf, avoid application near its eyes. Do not use caustics in rainy weather.

Figure 2. Dehorning paste is a caustic chemical applied to horn buds to destroy horn-producing cells.

Figure 3. The circle at the base of the ear shows the location of the horn bud in a young calf. The horn bud is readily visible after pushing back the hair. Reposition the hair over the paste and bud after applying the dehorning paste.

 

Hot iron dehorners are available in versions heated by a furnace or fire, 12-volt battery, 120-volt electricity, power packs (e.g., Buddex™) or LP gas (Figure 4). The head of the iron is a hollow circle and it fits over the horn bud. Proper application of the hot iron will destroy the horn-producing skin at the base of the horn. This technique works well for calves up to 12 weeks old. There are several sizes of dehorning irons. The proper size is one where the burner makes a complete ring around the base of the horn. For electric irons, use a short extension cord as voltage drops with a long cord, limiting the amount of heat generated by the dehorner.

1. Administer sedation, analgesia and local anaesthetic.

2. Preheat the dehorning iron to a red colour. Both electric and gas irons work best when they are "red" hot.

3. Wear gloves to protect your hands.

4. Hold the calf's ear out of the way to keep it from being burned.

5. Place the tip of the burner over the horn and apply slight pressure. When the burning hair begins to smoke, slowly rotate the dehorner by twisting your wrist.

6. Continue the application of heat for 10-15 seconds. Do not leave the dehorner in place for much longer, especially in young calves. Heat can be transferred through the thin bones of the skull and damage the calf's brain.

7. Dehorning is complete when there is a copper-coloured ring all the way around the base of the horn.

8. The horn bud or button will slough off in 4 to 6 weeks.

Figure 4. An electric hot-iron dehorner will destroy the horn-producing skin at the base of the horn bud.

 Advantages and Disadvantages

Dehorning spoons or tubes provide a quick and efficient technique for removing horn buds in calves less than eight weeks of age (Figure 5). With this method, a sharpened metal tube cuts through and removes the horn-producing skin at the base of the horn bud. Use the proper size tube to remove the horn plus about 1/8 inch of skin around the entire horn bud.

Figure 5. A dehorning spoon or tube is used to remove the horn bud plus the horn-producing skin at the base of the bud.

 

Scoop dehorners are used for calves ranging in age from two to four months with horns up to four inches long (Figure 6). Some operators claim better dehorning with a rectangular-shaped scoop because it removes an even ring of skin around and with the horn bud. When used properly, it does not go too deep, but the dehorner can open the frontal sinus when used at the top end of the age and horn-size range. The blades must be kept sharp for best results.

1. Administer sedation, analgesia and local anaesthetic.

2. Close the handles together.

3. 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 (Figure 7).

4. 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.

5. Control bleeding by pulling the artery with forceps or using a hot iron to cauterize the artery.

6. Clean and disinfect the jaws of the gouger between calves.

Figure 6. A Barnes-type dehorner scoops the horn and horn-producing skin surrounding the horn base.

Figure 7. With young calves, the Barnes-type dehorner removes horn-producing skin but does not cut into the frontal sinus as shown by the arced line in Figure 7. In older calves with the horn attached to the skull, the dehorner cuts into the frontal sinus.

 

Dehorning and disbudding are surgical procedures. Calves require observation and aftercare following the surgery.

Diseases can be spread from animal to animal on dehorning equipment contaminated with blood. Enzootic bovine leucosis virus and the wart virus are two examples. It is essential to disinfect the tube and Barnes-type dehorners after each calf is dehorned.

The heat from electric dehorners effectively disinfects them between each calf. Hot-iron dehorners occasionally require cleaning with a wire brush. 

This document describes procedures and techniques for dehorning young calves. Advantages and disadvantages exist for each method. Producers should consult with their veterinarian for advice prior to attempting unfamiliar procedures. Pain control (sedation, anaesthesia and analgesia) is necessary for dehorning calves.