Calf scour: causes and control

Why is calf scour so important?

Calves are the future of the herd and often represent decades of work on herd development and genetics. Diarrhoea in calves is a common disease which may be severe; indeed it is the leading cause of morbidity and death in calves under one month of age¹ and accounts for roughly 50% of all calf deaths in the UK. Both beef and dairy farms are affected and the disease can cost up to £200 per affected calf², so calf scour is very important to the health, performance and productivity of every herd.

How to control calf scours?

Control of calf scours on farm can be a challenge, as the disease is multifactorial and the occurrence of clinical signs depends on the interaction between a number of factors:

• the pathogen(s) (pathogenicity, infectious dose, level of exposure)
• the environment (mixing with older animals, ventilation, hygiene)
• the calf (colostrum intake, health status, stress, nutrition).

The pathogen(s)

Diarrhoea may result from non-infectious causes, usually management, such as poor mixing, incorrect concentration or cold temperature of milk replacer, overfeeding or concentrate overload. Additionally, diarrhoea may result from infectious causes e.g. viruses and bacteria. Some common infectious causes are:

Bacterial causes: E. coli (K99)

In this case, the disease characteristically affects calves aged 0–7 days old when there is sudden onset of profuse yellow/white diarrhoea causing rapid and severe dehydration. Calves can quickly become recumbent. Accumulation of fluid in the abomasum and intestines gives the abdomen a bloated appearance.

Viral causes: rotavirus and coronavirus

Calves are most commonly affected with either or both viruses in the first 2–4 weeks of life. Typically rotavirus occurs slightly earlier; there is an acute onset of diarrhoea with very watery yellow/green faeces. Typical early signs include a reluctance to stand and drink, mild depression and salivation. Calves become dehydrated with sunken eyes and tight and inelastic skin.

Cryptosporidiosis

Cryptosporidium parvum diarrhoea is caused by the physical loss of absorptive area of the small intestine and exacerbates the viral infections described above. Calves are usually affected from around 7–28 days, with profuse yellow/green diarrhoea and mucus present. Dehydration is often only mild but calves can rapidly lose condition over 2–5 days and have a dull tucked-up appearance.

While morbidity is high, the mortality rate in uncomplicated cases is usually low.

The parasite causes epithelial destruction, resulting in diarrhoea due to malabsorption. It is able to undergo autoinfection and so can increase to high numbers in the host very rapidly; recumbence soon follows.

The approach to management, treatment and prevention of scour will vary according to the cause.

The appearance, volume and frequency of the scour are rarely diagnostic, so test faecal samples from scouring calves, to find out what bug(s) is/are a problem on your farm (it can often be more than one!). Work with your vet to come up with the best strategy for tackling the problem.

The environment

It is important to ensure that the calves’ environment is also playing its part in minimising the disease risk. 

The fundamentals of good calf housing: 

• All-in-all-out system
• Plenty of clean, dry, comfortable bedding – something that you’d be happy to lie on!
• Draught-free but well ventilated
• Avoid over-stocking. Minimal contact between multiple calves
• Good hygiene to reduce risk of spreading infection between sick and healthy calves. Don’t inadvertently transfer disease from sick calves to healthy ones – use separate equipment or disinfect between feedings.

There are several important things that can be done to help minimise the risk of infection from these pathogens and reduce incidence of calf scour:

Colostrum management 

Calves are born without any antibodies – the major line of defence against disease. Until they are able to produce enough of their own, they rely on antibodies provided in the colostrum.

A calf’s ability to absorb these antibodies into their bloodstream decreases rapidly following birth, disappearing completely by the time they are 24 hours old.

It is crucial that calves receive a sufficient quantity of colostrum, that is of good enough quality (contains enough antibodies and has minimal levels of bacterial contamination), quickly enough after birth. A gold standard approach to colostrum management will have a positive impact against many diseases; this involves:

• Quality – Good quality colostrum (>22% on a Brix refractometer)
• Quantity – equal to 10-12% of the calf’s birth weight. A minimum of 3 litres.
• Quickly – ASAP after birth, ideally within two hours, definitely within six hours.

Your vet can test blood from young calves for antibodies to give you a good idea of how effective your colostrum management practices are.

General health

Calves are exposed to common pathogens as soon as they are born, so the occurrence of disease will heavily depend upon the health of the calf.

Strong calves are healthy calves – ensuring calves are well fed and free from other diseases, including BVD and respiratory disease, will also decrease the risk of scours.

Calves are more susceptible to scours in stressful periods or situations, such as mixing groups, poor environment, disbudding, changing feeds and, in particular, extremes of temperature. Limiting stress in the calf will contribute to its long-term health.

Vaccination

Calves rely on antibodies from colostrum to protect them against the diseases that they come across in the first few months of life. Vaccinating the cow/heifer prior to calving with a vaccine against rotavirus, coronavirus and E.coli F5 (K99) ensures that her colostrum will contain high levels of these relevant antibodies. Calves fed colostrum from vaccinated cows will have increased protection against these specific causes of scours.

Protection of your calves against scours is very much in your hands. The key factors in reducing incidence within the herd can be planned in advance including housing, management and dam vaccination. By focusing your attention on preventative herd health, producing healthy and strong calves, the risk of scours is greatly reduced.

1. Milk Development Council report: calf enteritis and septicaemia. Project Number R6/95/10
2. Tilling O. (2018) Veterinary guide to rearing dairy heifers – a practical and easy guide. Context products Limited, Ashby de la Zouch, Leicestershire.
3. P (2009) Calf Management-Calf Scour-Beef and Dairy Rearer Units. NADIS.org.uk
4. Geollot S et al. (2018) Serologic and colostral response and vaccine efficacy in calves following a single injection of Bovigen® Scour in seronegative pregnant cows. BCVA conference, Hinckley.