All calves are exposed to a variety of micro-organisms such as viruses, bacteria and protozoa as soon as they are born. These micro-organisms are part of the environment in which cattle live and calves have to develop an immunity to them.

Keeping calves healthy requires good calf management which includes selecting robust calves to rear, ensuring the calves have received adequate colostrum within 6 to 8 hours of birth, having access to shelter and ensuring the calves receive appropriate feeding.

The two major types of problems seen in calves are:

1. Gut problems leading to scouring
2. Pneumonia

These two problems account for over 80% of all losses in calves, with scouring being the most common. Bloat, navel-ill, accidents and poisoning make up most of the rest.

Gut problems (scouring)

These can be divided into four major causes:

1. E. coli (white scours)
2. Salmonella
3. Rotavirus
4. Cryptosporidia

All these can occur separately or together. The visible signs as seen by the owner are scouring, a dry coat, the calf is dull and listless and in many cases dies in a short time.

Scouring is the result of changed gut function; that is, the germ makes the gut stop digesting, which increases the amount of manure and fluids the calf passes. Calves on a milk diet normally pass only a small amount of droppings. If the gut is affected, the amount passed can increase markedly. For example, the amount of water passed in a scouring calf can be 20 times normal. This extra water is mixed with salts and other food, so the calf is losing more than it can eat.

The loss of water and salts leads to dehydration. This causes shock and death. In other words, the germ that started the scour is usually not the direct cause of death. It is the shock caused by the loss of body water and salts that is the actual cause of death.

E. coli or white scours. The germ produces a poison that makes more fluid pass out than normal. This causes the shock mentioned above. On post-mortem, a calf that died from E. coli scours will often show no visible signs of having an infection.

Salmonella. These cause marked reddening of the gut by invading the gut wall. The result of this invasion is damage to the tissue, so that water and food cannot be absorbed. Salmonella can readily invade the rest of the body, causing blood poisoning and rapid death.

Rotavirus and Cryptosporidia. These agents damage part of the gut so that food is not used. This particularly applies to milk, which then goes sour in the gut. The germs normally present in the gut multiply rapidly in this sour milk, producing poisons, and so the gut works more rapidly to remove them hence the scouring. The water and food is also lost.

Prevention of scours

• The most important method of prevention is to provide adequate colostrum (beestings) in the first few hours after birth. It is only in the first few hours or so after birth that a calf can absorb the antibodies from the colostrum it drinks to give it immunity to many infections present in the herd. A calf needs about two litres of colostrum milk. Remember that heifer cows that do not mix with the herd may not have enough antibodies in their milk to provide suitable protection to their calves. To overcome this, and problems with sick cows or cows dying at calving, a store of frozen colostrum should be kept if a freezer is available. Remember that colostrum is more potent than any drug a veterinarian can sell.
• Provide adequate housing or shelter from the weather to reduce stress. Stress is important in allowing scours to develop.
• Maintain a suitable management and feeding system. Overfeeding and sudden changes of diet can cause further stress.

Treatment of scours

The most important thing to do is to replace the lost body water and salts. This is done by using electrolytes in their correct concentration. The earlier this is done, the better the response. Antibiotics can be used if necessary.

A treatment program could be:

1. Replace all the milk with electrolyte.
2. Use antibiotic if necessary (on veterinary advice).
3. Gradually replace electrolyte with milk over several days.

If calves are severely affected and will not drink, it will be necessary to call your veterinary practitioner to treat the calves with intravenous fluids. Force feeding can result in pneumonia, because very sick calves cannot swallow properly. Make sure affected calves are warm and dry. Exposure to the weather when sick will make things worse.

Pneumonia

Pneumonia is infection of the lungs and has many causes. Lung worms can play an important role in allowing infection to enter the lungs. A calf that survives pneumonia takes a long time to recover. This usually means stunted growth and poor production as an adult. Prevention is most important and this is by having suitable housing with adequate ventilation. Stress caused by exposure to cold, wet conditions, overcrowding and inadequate feeding can allow a calf to pick up pneumonia.

Treatment depends on the cause of the infection. If pneumonia is occurring, consult with your veterinarian for a diagnosis (which is often difficult as several causes may be occurring together). They will recommend a treatment program.

Other causes of deaths

There are many other causes of losses in calves but they tend to be isolated. Sometimes these losses may be severe on individual farms and immediate help should be sought in identifying the cause.

Things like plant poisoning, lead poisoning, leptospirosis, incidental infections and so on may all occur, because calves are curious and lick or taste any object lying around. Make sure that nothing is available to calves that may result in illness.