Diarrhoea or scour is the most common disease in young animals and, as a result, is the greatest single cause of poor growth and mortality.
The direct cost of treating scour can be easily determined from treatment costs and losses, but the overall indirect losses – including reduced growth efficiency across the wider group and, therefore, slower finishing – are often underestimated.
An Adas study in 2012 estimated that an average outbreak of scour in a 100-cow suckler herd costs £5,794 when the implications of calf mortality, treatment and growth reduction are taken into account.
Lauren Porteus, a farm vet at Scott Mitchell & Associates, gives advice on how to prevent and treat it.
What causes scour in young animals?
Scour is mainly caused by viral (rotavirus, coronavirus), bacterial (E coli, salmonella) and protozoal (Cryptosporidium parvum, coccidia) pathogens, which affect both calves and lambs. Nutritional scour can also be seen.
How can it be prevented?
Prevention relies on reducing challenge in the environment while maximising immunity, to slow development of infection.
Reducing the challenge
Maintaining good hygiene during lambing and calving environments is crucial to reduce the risk of scour. The pathogens that cause disease are found in the environment and are shed in the faeces of older animals that have developed immunity.
Therefore, minimising environmental contamination and build-up of scour bugs is essential.
Every attempt should be made to keep housing clean and dry, and reduce draughts, where possible. This needs to be maintained throughout the lambing or calving period.
Reducing the age range of batches is also beneficial to minimise shedding between animals with different ages and immune status.
Good colostrum management is vital for the best protection of lambs and calves in early life. Ruminant species rely on colostrum for antibodies, but colostrum also contains cells and proteins that work with the gut to reduce harmful challenge.
Good-quality colostrum production starts well before birth and relies on the mother’s body condition being correct, as well as good nutrition status. It is also affected by breed and genetics.
As a minimum, lambs need at least 5% of their bodyweight (50ml/kg) in colostrum in the first two hours of life, reaching more than 200ml/kg by 24 hours.
Calves require a minimum of 10% of their body weight in good-quality colostrum (measuring more than 22% on the Brix refractometer) within the first six hours after birth – ideally within the first two hours.
This equates to 4 litres for a 40kg calf or suckling continuously for two 20-minutes periods.
This may not be easy to achieve in sucklers, particularly when left to their own devices. In an AHDB study last year, only 63% of 49 suckler farms had adequate passive transfer of antibodies, with the rest receiving inadequate volumes or quality of colostrum.
You can improve protection against infections and scour using vaccines. These are given to the dam and rely on colostrum intake to transfer antibodies against rotavirus, coronavirus and E coli to the calf.
Other diseases can also have an effect on immunity. Bovine viral diarrhoea infection in calves causes immunosuppression and, therefore, makes animals more susceptible to infections.
Trace element status can be important in both lambs and calves, and in utero deficiencies, particularly in iodine and selenium, can result in weaker newborn lambs and calves that are slow to suck.
How should cases of scour be treated?
Diagnosis of the specific cause can help with management, additions to your treatment protocol and prevention – discuss this with your vet. However, the general management of scour, no matter what the origin, is rather uniform.
Scour results in two main issues – dehydration from loss of fluid, and electrolyte imbalances, which lead to acidosis because of the loss of salts. Correcting these and supporting gut healing is the primary treatment target.
The intensity of this treatment will depend on the severity of disease. Very weak calves that are unable to stand and have no suck reflex require veterinary attention and intravenous fluid therapy.
Other calves that are scouring, but less severely dehydrated, will require oral rehydration therapy (ORT). (See “Which oral rehydration products should you choose?”)
Early detection and treatment give the best chances of recovery and reduce the long-term effect on daily liveweight gain, productivity due to gut damage and decreased voluntary food intake.
It is also important to ensure scoured animals have access to fresh water, as they require extra fluid.
Scoured animals should be kept on milk. Milk provides the energy necessary for maintenance, growth and repair, as well as promoting gut healing and providing natural antibacterial activity. Milk feeding also helps maintain the normal abomasal pH
Which oral rehydration products should you choose?
Oral rehydration therapy (ORT) product requirements include:
- Energy provision to repair the gut and maintain growth
- Sodium supplementation to restore deficits lost in scour
- Alkalising agent to correct the electrolyte imbalance.
The electrolytes and alkalising agents included need to correct the imbalance, but not overdo it. Some alkalising agents can overalkalise the abomasum and, in doing so, promote the growth of pathogens such as E coli and salmonella.
This overalkalisation also interferes with the milk-clotting process and abomasal emptying, which can lead to further disturbances and make scour worse.
When considering which ORT product to use, the constituents and factors discussed above are important.
Many powdered ORT products can be effective for correcting the electrolyte balance, but most can only be mixed with water and should be fed two hours before milk, which can make management difficult, especially in lambs and suckler calves.
Rehydion gel can be fed with milk or, in animals that are up and about with a good suckle reflex, administered neat using a pump. In early cases, this is often enough to counteract the initial effects of scour and associated electrolyte imbalances.
The same delivery can be used in calves or lambs that have had a difficult birth to correct any acidosis straight away and prevent knock-on effects on vigour and colostrum intake.