Scour is the most common disease found in young calves, and the greatest cause of mortality.

Scour is the most common disease found in young calves, and the greatest cause of mortality, accounting for 50 per cent of all calf deaths, says Dr Graham Shepherd of G Shepherd Farm Animal Health. While calves can recover from scour, they may experience reduced growth, delayed calving, and reduced lifetime production as a result.

Both infection and nutritional issues can cause calf scour says Dr Shepherd, with diseases such as Rotavirus and Cryptosporidium being common causes. However, changes to milk consumption in terms of quantity and quality can be nutritional causes.  

“When calves scour their gut lining is damaged, results in less food being digested,” says Dr Shepherd. It also causes toxins which drive water and salt loss from the calf, and as a result, water and salts are directed into the bowel causing a large amount of watery diarrhoea. This results in the calf becoming dehydrated, says Dr Shepherd.

Blood and tissue fluids also become very acidic, which is too acidic for the calf to handle, causing acidosis. Dr Shepherd says: “Acidosis is a powerful depressant and is usually what will kill the calf.” Because of this, he advises always using an electrolyte with an alkalinising agent.  

Dr Shepherd says the two main electrolytes for calves in the UK, are either a sachet or a liquid. “Sachets containing an accurate amount of well mixed powder formulation are usually for mixing with water not milk,” says Dr Shepherd. He adds, water mixed formulations can be fed by stomach tube to calves that will not drink but can stand and have a suck reflex.

Liquid electrolytes are formulated for mixing with milk or a milk replacer. He adds: “These can be used when the calf is drinking voluntarily but should not be fed by a feeding tube.”

An advantage of liquid electrolytes, is their simple feeding, says Dr Shepherd. “By adding them to the milk or feeding alongside milk, the calf can still benefit from the milk’s feed value, which is important as starvation starts to affect the gut adversely after two days.”

In terms of what is in a good electrolyte, Dr Shepherd says: “Labels are complicated nowadays, the units are complex, and you need to be a chemist to work them out! But most reputable formulations fit into the recommendations.”

Water is the most important thing, says Dr Shepherd, as dehydrated calves need water. He advises in addition to electrolyte feeds, calves should always have access to drinking water. “Calves are 75 per cent water and need 10 per cent of their body weight in water per day.” He adds, diarrhoea can increase a calf’s water requirement between one and four litres per day.

The salt levels in electrolytes are well researched, including sodium, potassium and chloride levels says Dr Shepherd. He adds: “Products which are too low in sodium will not adequately restore hydration in the calf, but products which are too high may increase the risk of sodium poisoning, if access to water is not available.”

Dr Shepherd advises checking the label of liquid electrolytes when using them with milk powder. “Make sure the product is okay to be taken with a milk replacer, as whey-based milk powders can be high is salt.

Dextrose and glycine are components of electrolytes which help to drive water and salt back into the cells and the body. However, too much dextrose can be detrimental, says Dr Shepherd. Dextrose is included within formulations to help rehydration, but is not a food source, so calves benefit from milk as well. Whereas glycine is not required with milk products as the milk provides enough amino acid on its own, says Dr Shepherd.

Bicarbonate or similar alkalinising agents are used in electrolytes to neutralise the excess acid in the calf’s blood and tissues, says Dr Shepherd. He says Bicarbonate and citrate are good but should not be fed with milk or within a four-hour window after being fed milk. Acetate is a better alkaliniser, that is, it is better at correcting the acidity in the blood that results from scours.

In terms of scour management, Dr Shepherd advises to always suspect scour if a calf looks dull or is slow to feed. “Sometimes if the calf is just starting to scour, the diarrhoea can be watery and is not seen on the bedding,” says Dr Shepherd. He advises taking the calf’s rectal temperature to stimulate the flow of scour.

Dr Shepherd advises feeding electrolytes early, with the simplest method of feeding being to add a liquid electrolyte into the milk for two to three days, with clean bedding and access to water. “In obvious cases calves will be dopey, unable to get stand, with a poor suck reflex, sunken eyes, and diarrhoea. Whereas in severe cases the calf will be found in a coma,” says Dr Shepherd.

He advises oral rehydration therapy as the standard nutritional support for scouring calves with a good suck reflex, which can stand and only show mild depression signs. If the calf is standing, but has a weak suck reflex, Dr Shepherd advises being ‘aggressive’ with water based oral fluids, fed by a stomach tube. “If the calf is unable to stand or has no suck reflex, you need veterinary advice, as it will need intravenous fluids.”

Dr Shepherd adds: “If scour is common or severe then you need to involve your vet to diagnose the cause. Reaching the true cause can often be less than straightforward and is often a mixture of issues.”