Diarrhoea or scour in calves is not a disease in itself but a symptom of a misfunctioning or damaged gut. It is the calf’s gut that absorbs water and nutrients from the food that the animal consumes.

In many cases, dehydration or starvation kills a scouring calf and not the organism that caused the scour.

Parasites and viruses are the main causes of scour in young calves. In decreasing order of commonality, the main agents causing scour on Irish farms are cryptosporidia (parasite), coccidia (parasite), rotavirus (virus), coronavirus (virus), salmonella (bacteria) and E coli (bacteria).

Contrary to popular belief, scour is seldom caused by overfeeding alone – there is generally another underlying cause.

Where a calf is scouring, remember the two Rs – remove and rehydrate.

Remove the calf from the environment to a clean isolation area. This takes the disease pressure away – the causative agent was potentially picked up here. Our sick calf is also a source of future infection for others too. Calves should be temporarily taken away from the cow too – she could well have been a source of infection. Take care when doing so.

A scouring calf needs four litres of fluid daily on top of his usual feeds. Use oral rehydration solutions for this. They will contain electrolytes and readily usable energy sources like glucose.

Offer these solutions separately to the calf’s normal milk feeds and adhere carefully to the guidelines for preparation, using clean, warm water. These can be given through a stomach tube if the calf is a slow drinker. However, we should try to avoid giving the calf their milk feeds using a stomach tube if at all possible.

When a case of scour is highlighted initially, avoid going straight in with an antibiotic unless the calf is very weak or has an accompanying temperature over 39.5°C. If the scour has been caused by a virus (rotavirus/coronavirus), then it will have no effect.

Prevent a scour outbreak

Good colostrum management is the first and most important line of defence against scour. The antibodies that will form the calf’s immune defence against scour-causing agents will be derived from this first feed.

On suckler farms, if in doubt, intervene and give colostrum to new calves.

We want two litres in our calf, twice in the first six hours. It takes a calf around 20 minutes of suckling to consume this volume (two litres).

Next on the list is cleanliness. The cleaner the environment, the fewer bad bugs it will contain. Top up bedding regularly. Use the knee test as a guide – you should be able to kneel down on the bed and rise again with dry trousers.

Clear out calving pens every few calvings and disinfect when doing so. Try to have cows clean coming up to calving too. This might mean putting them out on to straw a week or more in advance of their due dates to clean off.

Vaccinating cows with Rotavec Corona will help prevent viral scour, though proper colostrum management is crucial or the vaccination will not be effective.

Feeding cows soya in the weeks pre-calving can also have a positive effect on colostrum quality and volume.

Scour agent in focus – Cryptosporidium

Crypto-based scour has become more prevalent in recent years. It triggers an extremely aggressive scour that can lead to big losses and takes a huge labour input to deal with.

Crypto scour generally occurs in the second week of life. It can be hugely difficult to eradicate as many disinfectants do not work against it (see right).

An infected calf will shed billions of crypto eggs – only 10 are needed to establish an infection. Older animals can also act as reservoirs for the disease, without themselves showing signs of infection.

Halocur

It is transmitted via the faecal-oral route. As well as isolating and using oral rehydration solutions, infected calves can be given halofuginone lactate (halocur), which reduces the severity of the disease.

If one calf in a group/shed developed crypto scour, it is advisable to administer halocur to other, non-infected animals to reduce the chance of the disease spreading and taking hold.

A general halocur treatment plan lasts seven days and a calf receives 10ml/day. Once crypto gets into a herd it often will persist for a number of seasons.

Some farmers will use halocur as a preventative measure for years following an infection.

Halocur cannot be used on dehydrated animals and can be toxic if overdosed.

Bedding

We need to replace our bedding twice as frequently where there is crypto scour on a farm. Try too, to keep newborn calves with other very young calves, avoiding them mixing with animals four days older or more.

When isolating infected calves, keep them away from others for at least a week after the scouring stops.

An important point of note is that crypto can spread to humans and cause diarrhoea, so proper hygiene is vital.

  • Effective disinfectants against crypto: 2-3% Keno Cox, 2-4% Neopredisan, 10% Ox-Virin, 3% Hydrogen Peroxide.
  • Steam-cleaning sheds between calving seasons will also help stop reoccurrence.
  • Quarantine bought-in animals for one week.
  • Don’t handle healthy stock after handling known infected animals.
  • Raise water troughs to at least 0.75m off the ground.