Main causes of calf mortality

Stillborn calves make up a large proportion of what we see in the post-mortem (PM) room every day at this time of the year. This is frustrating for farmers as they are often present at calving, but a dead calf is still delivered. In the PM room, we check some or all of the following, depending on the history on the farm.

There are other causes of stillbirths so, if you are encountering this problem, discuss it with your vet and always investigate the cause of it by submitting stillborn calves to the laboratory and/or taking blood samples.

Scour

Scour (diarrhoea/enteritis) is consistently the most common cause of death in the PM room at this time of year in calves less than one month of age.

Typically, the calves’ eyes are very sunken and their skin is dry due to dehydration and they have a dirty tail and perineal area (back end). When we dissect them, the intestines contain abnormal fluid contents and they may have milk in their rumens (milk should go into their abomasums) and, sometimes, they will have small ulcers in their stomachs.

Rotavirus and cryptosporidium are the most common causes of scour that we diagnose in calves aged one to three weeks old in the Regional Veterinary Laboratories.

The intestines in these animals are severely inflamed, with loss of the intestine’s capacity to absorb fluid evident on microscopic examination. Often, we diagnose both agents in the same animal. Obviously, this will make the disease even more severe.

Less commonly diagnosed causes of calf scour that we see include E coli K99, which usually affects calves in the first week of life, and coronavirus which generally affects calves one to three weeks of age. Coccidiosis and salmonellosis typically cause bloody diarrhoea in slightly older calves.

Septicaemia

Septicaemias and/or toxaemias are another common cause of death in young calves submitted to the Regional Veterinary Laboratories at this time of year. This occurs when bacteria or their products enter the blood stream and set in train a series of events that cause the calf’s system to “shut down” and go into shock causing death of cells and eventual death of the animal.

The calf will be dehydrated and have a very high heart rate. It will initially run a very high temperature and then collapse with hypothermia.

E coli is the bacterium most commonly isolated from these cases.

The most common source of this infection is through the navel. In some of these cases, the infection is not obvious from the exterior, but when we dissect the animal we easily see the infection moving up from the infected navel and affecting the liver and kidney and joints of these animals.

Respiratory infections

Respiratory tract infections (pneumonia) are another important cause of death in young calves and are the most common cause of death we see in the PM room in calves between one and three months of age. Bacteria, including Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis and Histophilus somni, and viruses, including RSV, PI3 and IBR, are frequently detected in these cases.

In addition to death in the most severely affected calves, pneumonia can cause serious ill-thrift in less severely affected calves. If the problem is not diagnosed and animals are not treated properly and early, then they can become poor thrivers all their lives as a result of chronic ongoing respiratory disease.

Metabolic conditions

Nutritional/metabolic conditions are regularly diagnosed in the PM room as the cause of death in young calves. Hypogammaglobulinaemia occurs as a direct result of the calf not receiving enough good quality colostrum at the right time.

Ruminal drinking occurs when milk goes directly into the rumen (first stomach), which it should normally bypass and go straight into the abomasum (fourth stomach). The rumen cannot digest milk properly and when milk enters it the contents quickly become acidic, leading to lactic acidosis.

Ruminal drinking can occur if there is failure of the oesophageal groove. Typically, failure of the groove to close arises in trough or bucket-fed calves that gulp rather than sip the milk.

Whether or not your calves develop any of the problems mentioned depends on the how the calf is managed.

Colostrum management

The greatest factor in ensuring that the calf can fight infection in its early life is whether he/she gets enough good quality colostrum/biestings at the right time.

Do not take the chance that the calf will suckle the cow themselves. This is a high-risk practice and will increase the number of calves in your herd that will not have immunity to neonatal infections. Only 50% of dairy calves will receive adequate colostrum if left with the cow to suck.

Vaccinations

Cows can be vaccinated before calving to prevent calves getting scour, but obviously it is only successful if the calf gets colostrum and enough of it and at the correct time. Feeding of transition milk for a number of feeds will also help as calves are getting milk with higher nutritional value. Vaccines are also available against some but not all of the causes of pneumonia.

The first thing is to diagnose your problem. It is important to correctly identify the agent that is causing the scour or pneumonia.

It is important to take faecal samples from animals for testing before you treat them. Your vet can take nasal swabs from fresh pneumonia cases for testing. It’s also worthwhile to get your vet to refer any calves that die to the Regional Veterinary Laboratory for post-mortem examination.