About 50 per cent of all deaths in young calves are caused by calf scour (diarrhoea), with the most common cause of death being dehydration as a result of increased loss of fluids.
The cost of a case of scour is estimated at £44. This includes drugs administered, potential losses and decrease in the value of the calf.
It is important to address the causes to avoid unnecessary financial losses and impacts on welfare.
Tim Potter, vet for Nadis, says: “Calf scour is easily recognisable and it is vital we do not tolerate it on farm. We have to work to reduce its impact and treat affected animals appropriately and rapidly.”
Damage to the gut as a result of scouring can have a long-term impact on performance and daily live weight gain, causing slower growth and increased cost of production.
It is difficult to say exactly what pathogen is causing scours just by looking at a calf, as the signs are indistinguishable. However, there are a number of potential causes.
The most common viruses would be rotavirus and coronavirus, bacterial causes are usually E.coli and salmonella, and there are groups of protozoa such as cryptosporidia and coccidia.
Scours can also be caused by nutritional imbalances and calves usually appear happy and healthy if this is the case.
With viruses such as rotavirus and coronavirus, infection is often acquired in the calving pen and introduced into the calf shed by the infected calf.
There are vaccines available for rota and corona viruses. They work by being administered to the cow to boosts antibodies and immunity, which are then passed onto the calf through the colostrum.
Mr Potter says: “The vaccines can be very effective, but it is worth remembering that if you are investing in them, it is essential the calf gets sufficient good quality colostrum to ensure this immunity is transmitted from the cow to the calf.”
Bacterial infections such as E.coli are most commonly picked up in the calving pens, so it is vital to ensure good hygiene protocols around calving to minimise the levels of bacteria being picked up at birth. It usually affects calves aged one to three days, however can occur later.
Salmonella is another bacterial cause of scour and death rate can be as high as 60 per cent.
Often, neonatal calves infected with salmonella die within 12 hours. Older calves often produce a bad-smelling watery diarrhoea containing blood and mucus. Salmonella is zoonotic, so it is vital staff follow good hygiene practices.
Protozoal pathogens such as cryptosporidiosis can build-up in pens which are never emptied and properly cleaned, for example where new calves are constantly added.
Mr Potter says: “Crypto damages the lining of the small intestine which decreases the surface area for the absorption of water from the faeces, meaning it is lost in the form of diarrhoea.
“It can cause a mild dehydration, however the calf will lose condition over two to five days and appears dull and tucked-up. Like salmonella crypto is potentially zoonotic.”
Coccidiosis is another protozoa and is usually seen in older calves. It is believed most cattle kept in conventional conditions will come across coccidiosis at some point in their lives, however it is estimated only five per cent of animals will show clinical signs.
Despite this, all animals infected with coccidiosis will suffer some negative effect on their growth and feed conversion, which in turn has an economic impact.
Due to the wide variety of scour-causing pathogens, it is important to diagnose the responsible one, as there are different ways of treating each type of pathogen.
There are now a number of rapid diagnostic tools which can be used on farm and a diagnosis can be reached quickly to allow rapid treatment. However for coccidiosis, a faecal sample still needs to be sent away to a lab for diagnosis.
Fluid therapy is the most important part of treatment. If the calf can still drink, fluids can be given orally. If the calf can no longer drink, it may be necessary for a vet to administer intravenous fluids.
“Historically, farmers were advised to remove all milk feeds and gradually reintroduce them after a period of solely electrolyte feeding,” he says.
“However, this effectively starves the calf and it is now advised that electrolytes are given in addition to regular feeds. There is no benefit in withholding milk feeds.”
Rota and coronavirus are not treatable through the use of antibiotics, so rehydration therapy will be required. However it is worth investing in long-term prevention through the introduction of vaccination and good colostrum protocols.
Antibiotics are also not effective in treating crypto and coccidia, as they are protozoal pathogens.
Oral drenches containing halofuginone lactate can help with the control of crypto, but fluid therapy is key.
In some cases it may be also necessary to administer an anti-inflammatory to manage pain relief.