Energy and electrolytes are what scouring calves need most, as this update from Dr Ingrid Lorenz, chairman of the CalfCare Technical Working Group, Animal Health Ireland, explains.
Calf scours (diarrhoea) remain the most common health issue in young calves. They cause major financial losses to the Irish livestock industry every year and, just as importantly, lead to a great deal of stress and increased workload for the farmer. Since calf diarrhoea is a classical multifactorial disease, infectious, as well as environmental, factors contribute to its development. In general, sub-optimal management factors are either lowering the resistance of the calf or increasing the infectious pressure. The single most important factor for the prevention of calf diarrhoea (as well as other diseases) is colostrum management, followed by appropriate nutrition of the newborn calf up to weaning. Non-infectious causes increasing the infectious pressure relate mainly to housing and general hygiene. It may be difficult to prevent calf diarrhoea completely, especially in intensive farming systems However, once a scour develops, losses can be minimised through good management practices. A scouring calf, if housed in group pens, should be separated out and housed individually, to avoid infectious agents being spread to other calves.
The most common infectious causes in new-born diarrhoeic calves are cryptosporidia (a parasite) as well as rotavirus and coronavirus. Enterotoxic Escherichia coli (a bacterium) is rarely found in this context and, if at all, only causes diarrhoea in the first four days of life. If viruses and cryptosporidia are involved, the lining of the intestines is damaged, resulting in the loss of large amounts of body fluid into the gut. As a result, the calf quickly dehydrates, electrolytes become unbalanced, energy reserves are depleted, and the calf may develop shock and die. Once the damage is done, the calf will continue to scour until the intestines are repaired.
The single most important treatment for a calf with diarrhoea is the replacement of the fluids and electrolytes lost due to scour. These are best provided in the form of good quality electrolyte solutions (see Figure 1) which should be given in addition to milk feeds, for example at noon and at night. The feeding of electrolyte solution should be given as soon as you see signs of scouring. If it is left too late, the calf may have already have lost too many fluids and electrolytes to be treated successfully with oral solutions. If a calf refuses to drink the oral electrolyte solutions, it can safely be given by stomach tube or drench. This is also an option for a suckler calf as it is unlikely to drink the solution from the nipple bottle or bucket. However, if a scouring calf refuses to drink milk or milk replacer, this should not be stomach-tubed. Milk given repeatedly by stomach tube will lead to the build-up of acids in the rumen and damage the ruminal wall. Therefore, it is not a recommended method for feeding of milk to calves that are not drinking due to ill health.
For the provision of energy, the scouring calf needs as much milk as the healthy calf (at least 6L per day for an average-sized Holstein calf). Scours have often been blamed for weight loss or ill thrift in young calves. However, research has shown that a scouring calf can digest milk almost as well as a healthy calf. This means that a calf can gain weight even while scouring, provided it is fed correctly. A scouring calf should be kept on milk or good-quality milk replacer while it has diarrhoea. Feeding of milk has no adverse effect on the scour, but its withdrawal can lead to emaciation and death from starvation. The advice, therefore, is to maintain a normal feeding regime for dairy calves, and to leave beef calves with their mothers.
Since most cases of neonatal calf diarrhoea are caused by parasites or viruses, antibiotics cannot be of immediate benefit. The indiscriminate use of antibiotics increases the risk of the development of resistance to antimicrobials, and, therefore, they should not be used in uncomplicated cases of calf diarrhoea. If, however, calves are severely sick (dehydrated, not drinking and depressed, bloody faeces) or if they have fever, there is an increased risk of bacteria entering the bloodstream and causing septicaemia. In these cases, calves should be treated by your veterinary practitioner, preferably with injectable antimicrobials with a spectrum that includes gram-negative bacteria. Antibacterials used as last resort in human medicine (eg. fluoroquinolones, third/fourth-generation cephalosporins) should only be used in single animals for a limited number of strict indications where other antibiotics fail.
The use of halofuginone can be considered, if cryptosporidia are identified as a problem in your herd. Halofuginone is licensed to protect against cryptosporidiosis. To be of benefit, it has to be given as a preventive and according to the manufacturer's instructions. However, halofuginone on its own is unlikely to solve a cryptosporidia problem if general hygiene is not improved along with the treatment. The infective stages of cryptosporidia are resistant to inactivation by many of the disinfectants commonly used on Irish farms. Therefore, correct cleaning and the use of effective disinfectants are paramount when fighting cryptosporidia problems. Also, it has to be emphasised that cryptosporidia can cause diarrhoea in humans, so personal hygiene is very important when dealing with sick calves. For more information, see Animal Health Ireland (AHI) leaflet, Cryptosporidiosis in Neonatal Calves.
If scouring calves are in poor condition (down, not drinking, eyes sunken, very sleepy) your veterinary practitioner should be called to assist and give further treatment, such as intravenous fluids.
If calf scour is a problem in your herd, your veterinary practitioner can also investigate what infectious agents are involved and give you advice on the best measures for prevention and treatment.
Figure 1. Minimum ingredients required in commercial oral rehydration solutions.
Oral rehydration solutions should contain:
Glucose and/or another facilitator of the absorption of sodium and water;
An alkalinising capacity of 60-80mmol/L from bicarbonate or bicarbonate precursors (the strong ion difference can be calculated to assess the alkalinising capacity: SID = alkalinising capacity = [Na+]+[K+]-[Cl-]);