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Restoring the electrolyte balance (Oct 2021)

Calf dehydration: what are the signs? And how should producers administer therapy? A leading cattle vet shares his tips and pointers.

Scours remains a significant challenge to calf health, accounting for around 50% of all mortalities, and is the cause of huge financial losses to UK dairy businesses. Scours or diarrhoea are typically the result viral or bacterial infection, and sometimes parasites. But, irrespective of the cause, mortality in affected calves is typically the result of dehydration and electrolyte disturbances.

So says Westpoint Vet’s Tim Potter, stressing that this means the single most important part of any treatment programme for scours and diarrhoea is rehydration therapy.

Tim Potter from Westpoint Farm Vets

“Producers must first assess the degree of dehydration,” he says. “Diarrhoea results in excessive loss of electrolytes and fluid, via the faeces. The average faecal losses are around two litres per day, but can be as high as six litres. And if this fluid loss is not replaced, the calf will rapidly become dehydrated and the animal can become extremely sick very quickly.”

Dehydration is often expressed as a percentage of water loss relative to the animal’s total body weight. The higher the dehydration percentage, the more severe the symptoms. Dr Potter says dehydration can be estimated through visual assessment of scouring calves.

“Check their demeanour – how is the calf responding to feeding and stimulation? As dehydration becomes more severe, calves lose energy, grow lethargic and show signs of depression,” he says. Skin elasticity, often referred to as ‘skin tent time’, is a test producers can use to determine the level of dehydration. “Pinch a fold of skin on the side of the calf’s neck and rotate it 90 O. Let go and then time how long it takes for the skinfold to disappear. In a healthy and well-hydrated calf the skinfold will disappear in under a second.”

Sunken eyes can also be an early sign a calf is ill. This is best assessed by pulling down the lower eyelid and measuring the gap at the corner of the eye from the eyelid, according to Dr Potter. For calves that are less than 8% dehydrated, oral rehydration is typically sufficient. For severely dehydrated calves (greater than 8% dehydration) oral fluid therapy is unlikely to be enough. “In this instance, producers should call their vet to administer fluids intravenously,” stresses Dr Potter.

Quicker absorption

Oral electrolyte therapy can be administered either by a bottle fitted with a teat or by stomach tube. Absorption is slightly quicker following suckling, tubing is frequently used as it is less time consuming. “There are a large number of oral electrolyte products currently available and vary, considerably, in their constituent ingredients. Again, your vet will be able to offer advice on the best product to use,” says Dr Potter.

And he stresses it’s important not to underestimate how much fluid calves need to rehydrate. “Producers can use the percentage dehydration determined from examining the calf to roughly estimate the volume of fluids required, simply by multiplying this figure by the calf’s weight.

A 50kg calf, for example, which is 8% dehydrated needs 50 multiplied by 0.08 litres – four litres of fluid – to replace what it has lost. “And remember this should be on top of ongoing losses and what a calf requires for normal maintenance. So avoid trying to replace the deficit in a single electrolyte feed.

“The maximum amount of electrolyte producers should administer as a single feed is two litres, so it will usually be necessary to provide a scouring calf with additional electrolytes repeatedly for several days,” he adds.

Oral electrolytes

And, typically, oral electrolytes should be fed as an extra meal to calves with diarrhoea. For example, where calves are fed twice a day (morning and evening), oral electrolytes can be fed as an additional feed in the middle of the day.

“There have been suggestions that continued milk feeding worsens diarrhoea and that treatment protocols should involve a period of ‘resting the gut’, during which milk is withheld,” says Dr Potter. “But research has shown that milk feeding does not worsen or prolong cases of diarrhoea, nor does it slow down the healing of the intestine. Studies have also shown that continuing to feed milk alongside electrolytes maintained growth and avoided the weight loss observed in calves only given electrolyte solutions.

“So it’s best to continue to feed milk as per the calf’s normal schedule and then add in additional electrolyte feeds.”

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