Calf Scours – A Vets View

Calf scour is one of the biggest health issues in youngstock and there is a seasonal peak in winter. There are several different infectious causes, but often once calves are run down, they suffer mixed infections.

Which type of scour do my calves have?

Scour can also be nutritional – for example from feeding badly mixed or poor quality milk replacer – but usually even nutritional scour has an infectious component, because once the gut is damaged, it is all too easy for the pathogens to take hold. The most common bugs on UK farms are Rotavirus, Coronavirus, Cryptosporidium and Coccidiosis, which are probably present on all cattle farms to some degree. Other pathogens include Salmonella and Enterotoxic E coli (a particular strain which causes gut damage) – but these bacteria are limited to certain farms.

So, every farm has bugs, whether the calves get disease or not depends on hygiene, management and immunity. It is not possible to tell which pathogen is the cause of the scour just by just looking at the diarrhoea, which can be very variable, from profuse watery to sticky yellow, to green and mucous. The one exception perhaps, is coccidiosis which tends to be in older calves and can have fresh blood in it due to straining. Salmonella will also commonly cause a bloody scour (and a particularly sick calf). Your vet will be able to help you make a diagnosis based on sampling affected calves.

How should I treat my scouring calves?

Most calf scour in the UK is caused by either Rotavirus or Cryptosporidia, or a mixture of both. Neither are bacteria, so antibiotics have no effect. There may be some indication for antibiotics to protect against secondary bacteraemia (bacteria in the blood) and secondary E coli proliferation in the gut, but it is best to seek advice from your vet on this. Many vets are now specifically advising NOT to routinely use antibiotics, as they can interfere with healthy gut bacteria, and there is good evidence that calves can recover better without. However, the diagnosis is important: salmonellosis, for example, does warrant antibiotics.

If cryptosporidia has been diagnosed, treatment options are limited but halofuginone is a licensed anti-protozoal which can be used on veterinary advice. It works better as a preventive though.

The mainstay of treatment should be replacement of lost fluids. This is normally done with oral electrolytes, which are formulated to aid water absorption via the intestine. Scouring calves also become acidotic and whilst all electrolytes help them counter this, modern electrolytes usually contain alkalising agents too. There is a large range of products available and some are more sophisticated than others.

Traditionally, milk feeds were stopped for a few feeds while the calf was fed electrolyte fluids. However, this advice is now largely outdated as calves loose weight very rapidly when not fed milk
the energy in electrolytes is for water absorption, not nutrition for the calf, and is far less than is contained in milk or milk replacer. The concern is that by continuing to feed milk, there is more secondary fermentation in the gut and the calf continues to scour. To some extent this is true, but more attention should be paid to the demeanour of the calf rather than what is coming out of the back end. The research evidence is that calves which continue to receive milk in addition to electrolytes (to replace lost fluids) recover faster and lose less weight. Some modern electrolytes can be fed mixed in with milk, although the older types are best fed as additional separate feeds.

As scour is due to an inflamed gut, anti-inflammatories are also useful in the treatment of scour. They make the calf feel better too, and so she is more likely to continue to drink. Severely dehydrated or collapsed calves will benefit from intravenous fluids (a “drip”) as they lose the ability to absorb fluids from the gut.

How can I prevent scour?

Prevention is the key! Once a calf has scour, the damage is already done. It is useful to think where the infection initially comes from. Most scour outbreaks begin with the calves being infected from their mothers or other adult cows in the herd. Many adults are symptomless carriers of the common scour pathogens. The calving box/area is therefore one of the key routes of infection. Scour may be occurring at 7-10 days old, but the initial infection is often much earlier than this (7-10 days is the typical incubation period for Rotavirus, for example). Of course once a batch of calves has started scouring, infection circulates amongst them and can become a continuous cycle.

Some tips to reduce the cycle of infection are:

  1. If from a dairy cow, remove the calf as soon as possible after birth into an individual, clean pen.
  2. Rear young calves in individual pens, disinfected between calves.
  3. Wash and sterilise all milk feeding equipment well.
  4. Rotate calving boxes/ clean out well – ideally after every calf is born. If in a loose-housed calving area, clean out regularly and provide plenty of space.
  5. Use appropriate disinfectants: e.g. coccidiosis and cryptosporida are particularly resistant, so require particular disinfectants such as Kilcox.
  6. When scour is a problem in suckler herds, a change of environment is recommended. Can the next cows to calve be housed elsewhere, or calve outside?
One reason why scour is most common towards the end of winter may be because the pathogens have built up in the pens and calving areas such that they overcome the calf’s defences. As well as reducing infection levels (basically, hygiene), the other part of the equation is maximising the calf’s defences, or immunity. For most of the scour pathogens, protection from colostrum is vital. Feeding enough colostrum of good enough quality, and soon enough after birth is well known, but UK research shows that around half of all calves have inadequate antibody levels. Your vet can do a simple blood test on 4-10 day old calves to check antibody levels: if they are low, a review of colostrum management is a good idea. There are some great solutions available now for freezing, storing, thawing and feeding colostrum, such as the ColoQuick or Perfect Udder systems, which revolutionise the ability to smoothly and hygienically implement best practice without having to fumble around trying to thaw colostrum stored in old ice-cream containers, for example.

Vaccination of cows before calving can boost specific colostrum antibody levels for some of the pathogens: for example Rotavec-Corona boosts antibodies against Rotavirus, Coronavirus and K99 (E. coli). Not only will this raise blood antibodies in the calf against these diseases, but colostrum fed longer will line the gut with protective surface antibodies. In the case of suckler calves, they will continue to receive some protection as theysuckle the dam, but in dairy calves the additional benefit is seen if colostrum is fed at least partially for the first 5-6 days or so. The risk of Johnes disease precludes most farms from pooling colostrum, but spare colostrum from an individual’s mother can be stored with a longer “shelf life” using a buffered acid such as MilkMate®. Cryptosporidiosis can be a particular problem as colostral immunity seems to play a much smaller role. In this case, ensure there is no mixed infection or other factor which is decreasing the calf’s ability to fight off the disease, and redouble efforts on hygiene to break the cycle of infection.

Some tips to maximise immunity:
  1. Keep calves warm: calf coats are an obvious solution; deep straw bedding allows nesting.
  2. Keep calves dry: wet calves are cold calves, and bugs also like the damp.
  3. Good nutrition: feed a quality milk replacer, and in good quantities. Top performers are feeding much more than litres twice daily nowadays. Thin calves are more susceptible to disease. Calves need more feed when it is cold.
  4. Ensure a good first feed of colostrum: e.g. 4 litres within first 6 hours of birth. Test colostrum quality, and don’t rely on chance.
  5. Top up colostrum antibody levels using vaccination of the dam (for rotavirus, coronavirus, K99 E coli, or salmonellosis).
  6. Don’t stress the calves: feed consistently and with care.
  7. Continue to feed colostrum for as long as possible: antibodies can no longer be absorbed after 24 hours, but will line the gut.

Can the scour bugs affect us?

Finally, be aware that Salmonella and Cryptosporidiosis are zoonotic diseases, and can affect humans. The very young and very old are particularly vulnerable to more severe disease.
Written by Owen Atkinson MRCV’S – Dairy Veterinary Consultancy Ltd
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