Calf Scours

Calf scours

Diarrhoea, or calf scours, is the most common problem seen in young dairy calves. Farms experiencing sickness in more than 10% of calves or deaths before weaning of more than 3% should seek advice from a veterinarian.

Many causes of calf scours can be passed onto humans, particularly children, so it is important to maintain good personal hygiene whenever handling sick calves.

More information about calf scours can be found in Chapter 7 of Rearing Healthy Calves.

What to look for

• Diarrhoea, which can be evident on the tail and/or down the back legs. The consistency and volume can vary from profuse, watery diarrhoea to mucoid with or without blood
• Varying degrees of dullness, lethargy and disinterest in feed. Slow or incomplete milk feeding is often an early sign of sickness and these calves should be closely monitored
• Sunken eyes caused by dehydration
• Droopy ears
• Dry nose
• Reduced or absent 'suck reflex'. This can be tested by inserting a gloved finger into the calf's mouth. In a normal calf, this should initiate reflex sucking
• Some causes of calf scours may also result in sudden death

Causes

The most common infectious causes of calf scours include:

• Viruses such as rotavirus and bovine coronavirus
• Bacteria such as Salmonella species and E. coli
• Parasites such as Cryptosporidium (“Crypto”) or Coccidia (coccidiosis)

Calves become infected with these calf scour 'pathogens' via feed or water contaminated with manure or by direct ingestion of manure. This could be from licking walls, consuming milk or colostrum contaminated with manure and chewing contaminated bedding.

Digestive upsets due to changes in milk volume, quality, milk composition or temperature variations can also cause calf scours. This form of scours (milk scours or nutritional scours) is usually mild and calves remain bright and alert. However, if such changes occur when calf scour pathogens are also present, the stress of changing the diet can cause an outbreak of infectious diarrhoea.

Calves should have a consistent diet from birth to help reduce the risk of calf scours.

Animals likely to be affected

Calves are susceptible to the various causes of calf scours at different ages, which are outlined in the timetable below.

Confirming the diagnosis

A general diagnosis of calf scours is made by observation of diarrhoea in a young calf. However, it is important to determine the actual cause of calf scours to ensure the most appropriate treatment and to help with future prevention strategies.

Some treatments are very specific to the cause and an accurate diagnosis will help ensure the correct treatment in a cost-effective and timely manner. Specific calf scour pathogens can be diagnosed by submitting a manure sample to a veterinary clinic or by conducting a calf-side test using a special test kit.

It is essential manure samples are taken from untreated calves to give the best possible chance of getting an accurate and representative diagnosis. Laboratory tests can also check the susceptibility of any bacteria pathogens that are present to different antibiotic treatments.

Treatment

Electrolytes

Giving oral electrolytes to correct and prevent dehydration is the most important aspect of calf scours treatment. Scouring calves require six to 10 litres of fluids per day divided over at least 2–3 feeds. This total fluid requirement includes any milk feeds.

Scouring calves having difficulty standing or are unable to stand up, have sunken eyes, no suck reflex, feel cold and have a dry, sticky mouth require urgent veterinary attention or should be humanely euthanased.

Should I stop feeding milk?

Milk feeding of scouring calves should never be stopped for more than 24 hours as electrolytes do not contain enough nutritional value to sustain the calf.

Most veterinarians will recommend continuing milk feeding but in more frequent, smaller feeds. Sometimes withholding milk can reduce the calf scours and re-introducing milk can cause recurrence of scours again. It is important to remember that the gut of a scouring calf is damaged and needs time to heal, which is generally more than 24 hours.

Although re-introduction of milk can cause scours to recur, the nutrients provided in milk are essential for the calf to recover. All signs that the calf is recovering should be considered, such as willingness to feed and general attitude, as well as the presence/absence of diarrhoea.

With the vast majority of oral electrolytes, it is important to ensure at least two hours has elapsed between feeding electrolytes and milk and to never mix electrolyte powders into milk. This causes interference with formation of the milk clot within the calf’s stomach, which is critical for correct digestion. Always check the manufacturers instructions on how to administer electrolytes as the volume and mix rates are highly variable.

Antibiotics

Antibiotics are only effective against bacteria. They have no effect on viruses or parasites and will not correct dehydration. As such, antibiotics should only be used in scouring calves if:

• Laboratory or calf-side tests indicate pathogenic bacteria such as E. coli or Salmonella have been diagnosed
• There is blood in the faeces, suggestive of severe damage to the gut
• The calf is very depressed, weak or unable to stand, suggestive of toxins (produced by pathogenic bacteria) present in the blood

If a veterinarian prescribes antibiotics, it is essential the correct dose is given by the correct route for the correct duration. Clear records of all treatments should be kept, noting the calf ID, dates of treatment, nature of treatment and outcome. All treated calves should be clearly identified and designated feeding equipment used. Sick calves should be fed and treated last.

Blanket use of antibiotics or medicating large groups of calves should be avoided whenever possible and only ever done under the advice of a veterinarian.

Antibiotics and other veterinary drugs should be stored in a secure cupboard or the fridge (depending on the specific drug), out of the reach of children. All staff responsible for administering veterinary drugs should ensure they are adequately trained in this procedure.

Water

Fresh, clean water should be available to calves from birth, ensuring even very young calves can reach the water source. Scouring calves can become very dehydrated between milk feedings and will feel thirsty and drink water to help combat the effects of dehydration.

Risk factors

• Inadequate colostrum intake (quantity, quality, timeliness, cleanliness)
• Poor feeding hygiene, such as poor storage and handling of milk or contaminated feeders
• Inconsistent feeding routines (type, volume, temperature of milk feed)
• Poor housing management, such as continuous flow vs all-in all-out system
• Inadequate housing, such as wet bedding, poor ventilation, build-up of manure or a dirty calf trailer
• Overcrowding or mixing of calves of different ages
• Stress, such as disbudding, weaning, vaccination, turnout or transport
• Poor biosecurity, such as inadequate separation of sick calves

Prevention

Prevention of calf scours can be achieved by addressing the above risk factors. Good management alone will reduce the risk of calf scours significantly.

Colostral vaccines are available for calf scour pathogens. These involve priming the immune system of the cow to boost specific antibodies in colostrum which is then fed to the calf. The effectiveness of colostral vaccines relies on calves receiving adequate colostrum in the first 24 hours of life.

Typically, cows are vaccinated 10 to 12 weeks before calving followed by a second dose four to six weeks later. An annual booster is then given four to six weeks before calving. Label instructions should always be followed when administering colostral vaccines as the exact vaccination schedules can vary for each product.

More information about ensuring adequate colostrum intake and preventing calf scours can be found in the Rearing Healthy Calves manual.

Causes of scouring in older calves