Infectious scours - as opposed to nutritional scours - is the exposure to and infection by specific infectious agents, in the main:

  • Rota virus
  • Corona virus
  • Cryptosporidium parvum - virus
  • E. coli (K99 enterotoxigenic form) - bacteria
  • Salmonella - bacteria
  • Coccidiosis

With the exception of Salmonella, these pathogens are present on all farms. Every calf is exposed to them but not all develop disease. This depends on the calf's immunity and the amount of pathogens in the calf's surroundings. Understanding the impact these diseases have on the young calf can help reduce mortality and mitigate the long-term impact on a calf. Adequate colostrum intake by the calf is the first building block. An active, healthy colostrum immune calf will be well protected against normal pathogen levels and the possibility of infection.

The first 3 organisms on the above list usually cause diarrhoea at 7 to 21 days of age, while the common E. coli strains cause diarrhoea within the first few days of life. The E Coli bacteria attaches to cells in the lining of the gut and turn on the fluid pump mechanism to cause excess water secretion into the gut. (Enterotoxigenic scours. Dam vaccination is helpful with this form.) The viral scours are caused by decreased absorption of water from the gut as the virus kills the cells of the gut papilla. (Dam vaccination is available but not always effective). Both cryptosporidium and salmonella are zoonotic (transferable to humans), and are easily contracted without adequate protection and hygiene.

The severity of scours is determined by the:
  • number of organisms the calf is exposed to
  • amount or lack of calf immunity (colostrum)
  • stress on the calf
When should I treat the calf?
Calves that are alert and happy, still feeding and bright-eyed with yellow or white diarrhoea may only need light rehydration. The main indications for treatment are:
  • generally poor disposition
  • loss of appetite
  • level of dehydration
  • body temperature
Sick calf

If the calf is weak, depressed, or reluctant to move - something is wrong. Evaluate dehydration by pinching and pulling up the skin on the side of the neck or shoulder – this is called tenting. A normal calf's skin snaps back into position quickly. A dehydrated calf's skin remains tented for a varying period of time. The longer the tenting, the worse the dehydration. As dehydration progresses, the eyeballs sink away from the eyelids. This is a bad sign and fluids are needed immediately. Normal body temperature (use a rectal thermometer) is 37°C. Body temperatures less than 36°C and over 39°C are sign of problems and treatment should be started.

What are the recommended treatments?
  • Immediate isolation
  • Rehydration

The main treatment is rehydration therapy. Secondary treatments are antibiotics and nursing care. The main problem in scouring calves is loss of body fluid and electrolytes, so the water balance must be restored as soon as possible. Generally the calves are too sick to drink, so drenching them with an oral electrolyte is advisable. All electrolyte solutions contain glucose or a similar material, sodium chloride (table salt), and other electrolytes. The glucose and sodium allow the animal to absorb the water they need from their digestive tract. Smaller quantities, more regularly is advisable. Usually 2 litres of the oral fluid solution 3 x per day is about right. See our table for a guide to rehydration quantities.

If calf has advanced diarrhoea please consult your vet

Antibiotics are often given incorrectly to a scouring calf even though they are unable to kill most calf scours agents. If, due to damage in the gut of scouring calves, bacteria leak into the blood stream, antibiotics are of value for this reason. The huge negative is that antibiotics kill the good gut bacteria and often simply add to your health problems.

Consult with your veterinarian regarding the use of antibiotics to give

Be careful around scouring calves. Always treat them after feeding and attended to healthy calves. This will decrease pathogen transfer to the younger healthy calves. Remember keep all your all equipment clean - including hands and clothes.

General note on cleanliness around calves
Gloved hand
  • Have an antiseptic hand sanitiser fixed on a wall in the calf shed or use pump bottles as available
  • If you wear heavy duty rubber gloves in the rearing unit for cleaning and other activities, always put on a new pair of disposables before handling the calves' milk or meal
  • Dirty hands and gloves make it all too easy to transfer pathogens to bottles and nipples and stomach drenchers – then straight into the calf's gut!
When do I need additional help?

If your treatment methods are not working, contact your veterinarian immediately for additional help. If more than 5% of your calves are scouring and require treatment, or if scouring death loss is greater than 2%, contact your veterinarian.


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