Calf diseases, prevention and why colostrum is so important for the immune system

In terms of survival, the first few weeks for a calf are significant. As their bodies are still developing, they are not yet primed to effectively fight illness. It is important for a livestock farmer to be aware of these 3 common calf diseases and know what steps can be taken to prevent and treat them.

What exactly puts young calves at risk of developing disease?

Even though the immune system of a calf is functional at birth, it is less responsive than that of an older calf or adult bovine and has not previously been exposed to pathogens so is easily overwhelmed by the bacteria, viruses or parasites in the environment.

How can diseases be prevented?

The likelihood of disease in young calves can be reduced by preventative health measures such as proper nutrition, care, housing and following proper standard operating procedures.

Why is colostrum important to calves?

Passive immunity is acquired by young calves from their mothers, consisting mainly of antibodies. Young animals acquire passive immunity by transfer of antibodies across the placenta, or in the colostrum which is the first milk produced after parturition. Colostrum contains high levels of antibodies essential for the immunity of young to prevent catching diseases and aid fighting infection (Hammon et al., 2020). As well as providing antibodies, colostrum intake also supports the start of anabolic processes in several tissues, stimulating postnatal body growth and organ development. Calves are born with few antibodies of their own and an immature immune system that is not capable of producing antibodies for few weeks. Colostrum provides protection in the initial period where a calf’s immune system is maturing. Therefore, colostrum management may be the single most important management factor in determining calf health and survival (Godden, Lombard and Woolums, 2019).

Failure of passive transfer (FPT)  (no passive immunity acquired by the calf) results in three important diseases to look out for, during the first few days from weaning are. These diseases are typically septicaemia, diarrhoea and pneumonia.


Septicaemia is an infection of bacteria and toxins in the bloodstream. This usually occurs whilst the calf is in utero or after birth. Bacteria that typically cause septicaemia are usually either E. coli or Salmonella. Septicaemia is expensive and difficult to treat, with survival rates low.

Clinical signs to look out for:

  • Depressed
  • Weak
  • Reluctant to stand
  • Suckle poorly
  • Other signs may develop over time such as swollen joints
  • Diarrhoea
  • Pneumonia
  • Cloudy eyes


Pay close attention to the colostrum intake. Calves with inadequate or poor quality colostrum will be at increased risk of not being able to fight off these bacteria, leading to eventual entry into the bloodstream.


Diarrhoea is one of the most common cause of death in calves. The highest risk period is typically the first month after birth. Diarrhoea is caused by various organisms including E. coli. This bacterium crosses the gastro-intestinal tract into the bloodstream. (Cho and Yoon, 2014).

Clinical signs to look out for:

  • Loose faeces
  • Loss of appetite
  • Difficulty to get up


It is important to recognize these signs as soon as possible and begin appropriate treatment to maintain hydration and to prevent blood acidosis. In most cases, calves die of dehydration and loss of electrolytes. For this reason, fast treatment with fluids to correct dehydration is necessary. Prevention and control of calf diarrhoea should be based on a good understanding of the disease complexities such as multiple pathogens, co-infection, environmental factors, and feeding and management during the calving period before disease outbreaks.


Pneumonia is an infection of the lungs. Calves that develop pneumonia before weaning may also have failure of colostral transfer immunity, poor ventilation, transportation or grouping that leads to stress can contribute to the development of pneumonia. Noxious gases, dust and moulds in the air put calves at greater risk of developing pneumonia.

Clinical signs to look for:

  • Nasal discharge
  • Dry cough
  • Increased body temperature
  • Respiratory distress
  • Decreased appetite
  • Mucosal discharge


Good ventilation without draughts can reduce the risk of catching infection, together with keeping the calves dry. It is also important to clean feeding areas regularly. All calves must have one gallon of colostrum within four to six hours of birth to receive adequate immunity. Calves that are not given enough antibodies at birth are at increased risk for pneumonia and scours throughout the entire growing period. Antibiotics, anti-inflammatories or anthelmintics can be prescribed for treatment.

There are five key points to disease prevention:

1) Effective development of the calf’s immunity. This is supported by:

  • Adequate colostrum intake.
  • Feeding high quality calf milk replacer and concentrates.
  • Free access to fresh water.
  • A good vaccination programme

2) Biosecurity:

  • Know the disease status of the source herd.
  • Use and check colostrum status (contamination, quality).
  • Reject sick calves.
  • Isolate new animals on farm.
  • Practice good personnel hygiene e.g. foot baths placed outside calf houses, regular cleaning and disinfection of waterproof trousers/overalls/footwear.

3) Limit stress:

Stress inhibits the immune system of calves. Factors such as transportation, sudden feed changes, poor ventilation, crowding, temperature fluctuations and draughts can all impact the disease resistance of calves. Adequate planning, scheduling and management of farm personnel and ongoing monitoring of calves are key factors in alleviating sources of stress.

4) Minimise the risk of exposure to bacteria, viruses and parasites in the calves’ environment:

  • A broad-spectrum disinfectant should be used regularly to clean pens, railings, water troughs, feeders and other equipment and surfaces.
  • Well-bedded and well-ventilated housing with a good protocol around hygiene and calf husbandry will also help to minimise disease risk.

5) Create a management plan:

Keeping a careful watch on calves and intervening early if they are not thriving is crucial. If in any doubt as to the diagnosis or best treatment of a calf, contact your veterinarian immediately for advice.


Cho Y. and Yoon K.-J. (2014). An overview of calf diarrhea – infectious etiology, diagnosis, and intervention. Journal of Veterinary Science, 15(1), p.1.

Godden S.M., Lombard J.E. and Woolums A.R. (2019). Colostrum Management for Dairy Calves. Veterinary Clinics of North America: Food Animal Practice, 35(3), pp.535–556.

Hammon H.M., Liermann W., Frieten D. and Koch C. (2020). Review: Importance of colostrum supply and milk feeding intensity on gastrointestinal and systemic development in calves. animal, [online] 14(S1), pp.s133–s143.