There’s nothing more disheartening for a producer than seeing a healthy, bouncing newborn calf become weak, dehydrated and ill from diarrhoea. Calf scours is the most common cause of illness in young calves and the disease has a number of causes. Like all young and vulnerable animals, calves succumb rapidly to diarrhoea – regardless of the cause – and urgent treatment is required.
Common causes of calf scours
Infectious agents such as viruses (especially rotavirus), bacteria (E. coli and salmonella) and protozoa (including coccidia) are the most common causes of calf scours. More than one of these organisms can be part of the disease process.
Hand-reared calves are particularly vulnerable to scours, often caused by a poor quality milk substitute, over or under-feeding or poor hygiene and failure to properly clean feeding equipment. Once the gut becomes unsettled, bacteria and viruses can cause secondary infection.
Calf diarrhoea is obvious and needs little description. Other signs are important to monitor and include weakness, lack of interest in suckling and feeding, dehydration and sunken eyes. Scouring damages the gut lining allowing body fluids to enter the intestine from general circulation, causing dehydration. Pinch the skin behind the calf’s neck between two fingers – if the skin springs back into place, the calf is adequately hydrated. If the skin remains elevated for more than 3 seconds, treatment for dehydration is required quickly.
The most critical part of treatment is addressing dehydration and electrolyte and energy imbalances. This can be done in hand-reared calves that are still drinking by providing water with added electrolytes in between feeds. Calves with severe dehydration need intravenous fluids. This is the fastest and most reliable way to rehydrate any animal, and the most effective scour treatment – but fluids must be administered early.
Scouring calves need extra care. Separate from healthy calves and make sure they are kept warm and dry.
Faecal examination will confirm or rule out protozoa and worm eggs, although gastrointestinal worms are usually a problem in older calves.
The diet and feeding pattern of hand-reared calves must be evaluated, but regardless of the milk replacer being fed, the scouring calf should be given two feeds of water and electrolytes only four hours apart, then milk can be reintroduced. Additional feeds of water and electrolytes in between milk feeds will help maintain hydration.
Calves need about 10% of their body weight in milk or milk replacer each day to maintain hydration – ie a 30kg calf needs 3 litres daily. When dehydrated, up to 5 litres of fluid is required orally to achieve adequate hydration. Often this is impossible to deliver if a calf does not want to drink – and this is when intravenous fluids become essential.
Most scours are not caused by bacteria so antibiotics will not be effective. When a bacterial agent is suspected (E. coli or salmonellosis) short-acting antibiotics may be administered. It’s essential to take into account meat residues – calves treated with antibiotics must be withheld from sale until the residues have disappeared.
Colostrum (first milk) supplies important protective antibodies to all newborns – calves should receive at least two litres of colostrum within 12 hours of birth. It’s good practice to collect colostrum from older cows and store in the freezer to have on hand for emergencies.
Vaccination of cows and heifers in late pregnancy may be indicated in herds that have recurrent E.coli scours outbreaks. The vaccination boosts antibodies against E. coli in colostrum and helps to protect the calves from infection.
People and calves can share the same infectious organisms, especially bacteria such as E.coli and salmonella. Always wear rubber glove and pay particular attention to hygiene when treating and caring for calves with scours.