Whenever calves are reared, scour can be a problem and the launch of Locatim®, a new product you may have read about in the farming press, provides a good opportunity to review the subject and the role colostrum plays in prevention.

Locatim® is a highly concentrated dose of antibodies obtained from donor cows that are vaccinated against E. coli, rotavirus and coronavirus, but which are guaranteed free from TB, Johnes Disease, IBR and BVD. The 60ml dose contains the same quantity of antibodies as 6 litres of normal colostrum. It is given at birth to protect vulnerable calves when quality colostrum from a vaccinated cow is not available, or is not known to be safe with regard to Johnes Disease.

Locatim® is used to boost immunity in calves that would otherwise be at risk from scour because of poor colostrum quality or colostrum leakage, or because of scour problems in a herd that is not vaccinated for rotavirus, coronavirus or E. coli. It is also suitable for weak calves that are hard to feed. At the time a writing Locatim® is £23.50 excluding VAT and discount.

Scour

Data from veterinary laboratories suggests that in calves under about three weeks of age rotavirus is the most common cause of scour, accounting for approximately 40% of cases. The next most common cause is cryptosporidium (25% of cases), followed by coronavirus and E. coli (15% of cases each).

Rotavirus is present on every farm and the peak age when scour starts is about 10 to 14 days, though it can cause disease down to about 6 or 8 days. The scour is characterised by pale or yellow faeces, with or without mucus, due to milk being only partially digested. Often the first part of the small intestine, the duodenum, is the first part of the gut to be affected, with the virus passing along the gut over time. Different strains of rotavirus are known to exist but variations in the severity of disease on-farm may also be due to mixed infections with other bugs, particularly cryptosporidium. Coronavirus is very similar to rotavirus in many ways, but the virus attacks the gut further down than rotavirus and infection tends to be slightly more severe on average. Control measures are similar.

E. coli bacteria come in many different forms, only some of which are harmful to health, and those types that cause scour can be categorised according to how they affect the animal. The type of E. coli which Rotavec Corona® protects against is the enterotoxigenic form or ETEC for short. This type of infection results in a very profuse, watery diarrhoea in calves under four days of age that rapidly leads to severe dehydration. ETEC attach themselves to the lining of the gut by protein structures called adhesins and it is from these structures that the different strains take their names. The most common is called K99, and Rotavec Corona® protects against this type. K99 ETEC is only present on some farms. The enterohaemorrhagic forms (EHEC) cause a bloody scour in older calves and tend to affect the large bowel.

Colostrum

Scour caused by Rotavirus and E. coli can be prevented or controlled by vaccinating cows with Rotavec Corona® and ensuring adequate colostrum intake by the calf. Attention to hygiene is also important. It has been estimated that damp bedding in the calf shed increases the risk of scour twofold.

“A target for feeding colostrum is at least four pints in the first six hours”

A target for colostrum feeding is 6% of body weight in the first six hours. For a 40kg calf this is 2.4 litres, or four pints in old money. This can be fed in two meals but it is important not to wait too long before feeding the second meal. A container with a teat is useful but a stomach tube should be available for when calves can’t be persuaded to feed. Make sure the tube has been sterilised if it has been used to administering fluids to scouring calves.

After the first day of life, when a calf takes a meal the components of the milk are fully digested. However, in the first few hours of life, and until the first meal is taken, the antibodies in colostrum are absorbed whole into the calf’s bloodstream. The first meal triggers a change in the gut that prevents the antibodies in subsequent meals from crossing the intestine and entering the bloodstream, so the first meal should be a large drink of quality colostrum. Milk also contains antibodies, but in much smaller amounts and milk, or mixture of milk and colostrum, should be fed for at least the first two weeks of life so that rotavirus antibodies are always present in the gut. Calves can transfer antibodies from the blood into the gut to protect against rotavirus but an on-going supply from milk is important.

If you are concerned that calves have not taken enough colostrum or that the colostrum has been of poor quality a quick blood sample allows you to monitor the transfer of passive immunity from antibodies. The laboratory fee is £3.35 per sample for four samples or more.

Treatment of Scour

Fluid therapy with a good quality electrolyte solution is the mainstay of treatment for scour. Calves should receive 2 litres four times per day, depending on their size and the severity of dehydration. Mixing milk with electrolyte solutions or diluting milk is not recommended as the meal will not form a clot in the abomasum. This could lead to further digestive upsets and on-going problems. Sometimes oral rehydration is inadequate and fluids need to be administered into the vein to stand any chance of saving a badly affected calf. In addition to dehydration, the blood of severely scoured calves, especially those with rotavirus, becomes more acidic and this needs to be corrected using bicarbonate in the intravenous fluids.

Antibiotics are widely used even though most causes of scour are not primarily bacterial infections. They are usually given because it is not possible to be sure bacterial infections are not responsible in an individual case and because bacteria can be secondarily involved if the gut is inflamed or the normal gut floral is disturbed. Courses of antibiotics longer than five days are to be avoided.

Kaolin is used to increase the thickness of gut contents and to slow their passage through the gut. It absorbs toxins and soothes the gut. A tablespoon of kaolin powder is added to each meal.
In an outbreak of scour it is always worth speaking to your vet as control measures and treatments depend on determining the cause of the scour.