NEONATAL CALF SCOURS

Neonatal calf scours causes more financial loss to dairy producers than any other health problem in their herds. Calf scours is not a single disease; it is a clinical sign associated with several diseases characterized by diarrhoea. Regardless of the cause, diarrhoea in calves can become extremely costly and debilitating to your herd if not diagnosed and treated early.

The scouring calf loses fluids which can cause rapid dehydration. In addition to dehydration, scours causes electrolyte losses, (such as potassium and sodium) which in turn can lead to acidosis. This can happen quite rapidly in calves as they are much smaller than mature cattle and therefore have less to lose before becoming critically ill.

Infectious agents cause the primary damage to the intestine, but death from scours usually results from a combination of dehydration, acidosis and loss of electrolytes. The identification of infectious agents which cause scours, however, is essential for implementing effective preventive measures.

CAUSES OF CALF SCOURS?

The known causes of scours are grouped into two categories: (1) non-infectious causes, and (2) infectious causes. The non-infectious causes are often referred to as “predisposing” or “contributing” factors. Whatever they are called, there is a dramatic interaction between non-infectious causes and infection. Any effort to prevent infectious causes is usually fruitless unless serious control of contributing (non-infectious) factors are part of the overall program.

Non-infectious Causes of Calf Scours
Non-infectious causes are best defined as flaws in management which appear as nutritional shortcomings, inadequate environment, insufficient attention to the newborn calf, or a combination of these. The most commonly encountered non-infectious problems include:

1. Inadequate nutrition of the pregnant dam, particularly during the last third of gestation. Both the quality and quantity of colostrum are adversely affected by short changing the pregnant dam in energy and protein. Deficiencies in vitamins A and E have been associated with greater incidence of calf scours.
2. Inadequate environment for the newborn calf. Muddy lots, crowding, contaminated lots, calving heifers and cows together, wintering and calving in the same area, storms, heavy snow or rainfall, etc. are stressful to the newborn calf and may increase the chance for easy exposure to infectious agents. The wet and chilled newborn calf experiences a drainage of its body heat, may be severely stressed, and all too often lacks the vigour to nurse sufficient colostrum early in life.
3. Insufficient attention to the newborn calf, particularly during difficult birth or adverse weather conditions. The calf is born without scours-fighting antibodies. The calf will acquire these antibodies
   only by nursing colostrum early in life. Any effort to prevent scours by vaccinating cows is wasted unless the calf ingests colostrum in the first few hours of life. As the calf grows older, it loses its ability to absorb colostral antibodies by the hour. Colostrum given to calves 24-36 hours old is practically useless; antibodies are seldom absorbed this late in life.

Infectious Causes of Calf Scours

Infectious causes of calf scours may be grouped as follows:

Bacterial Causes:
- Escherichia Coli, Salmonella spp. and other bacteria

Viral Causes:
- Rotavirus, Coronavirus

Protozoan parasites
- Cryptosporidium, Coccidia

Some pathogens may be more predominant than others in a given area. It appears that cryptosporidum is more common than previously thought. Single infectious are common, but mixed infections (egg. E. Coli + cryptosporidium or coronavirus + Salmonella) are often reported.

BACTERIAL CAUSES OF CALF SCOURS

Escherichia Coli (E coli)
E. coli appears to be the single most important cause of bacterial scours in calves. Most newborn calves have a chance to pick up E. Coli scours infections from the environment, particularly when sanitation is marginal. There are numerous kinds of E. coli. Recent research indicates that the majority of E. coli strains able to cause diarrhoea first colonize (or adhere) to the calf’s gut. They do so by means of very fine, fuzz-like protrusions known as “pilli”. There are two main types of E.coli:

1. Intestinal Form (common)
   1. Most common form where the most predominant sign is pasty/watery faeces. In some cases this progresses to calves being dull, listless and recumbent. Without treatment these calves become increasingly dehydrated and die in 3-5d
2. Septicaemic Form (uncommon)
   1. Bacterial infection spreads throughout the entire body with severe, sudden onset of disease with death occurring in 24-48hrs. The younger the calves, the greater the chance for death from progressive, severe dehydration.

Salmonella
Salmonella produces a potent toxin or an endotoxin (poison) within its own cells. Animals may be more severely depressed following treatment with antibiotics because treatment causes the Salmonella cells to release the endotoxin, producing shock. Therefore, treatment should be designed to combat endotoxic shock while addressing the Salmonella infection. Calves are usually affected at six days of age or older. The source of Salmonella infection in a herd can be from other cattle, birds, cats, rodents, water supply or human carriers.

Clinical signs associated with Salmonella infection include diarrhoea, blood and fibrin in the faeces, depression, and elevated temperature. The disease is more severe in young or debilitated calves. Finding a membrane-like coating in the intestine on necropsy is strong evidence that Salmonella might be involved.

VIRAL CAUSES OF CALF SCOURS

Coronavirus and Rotavirus
Both of these viruses possess the ability to disrupt the cells which line the small intestine with resulting malabsorptive diarrhoea and dehydration. Coronavirus also damages the cells in the intestinal crypts and slows down the healing process in the intestinal lining. Furthermore, the damage caused by either corona or rotavirus is often compounded by bacterial infections and the risk for fatal diarrhoea is increased when mixed infections occur. Transmission is from adults carrying the infection and also from calves recovering from disease that continue to shed virus for up to 3wks.

Calves as young as one or two days old may scour from corona or rotavirus infection; however, most outbreaks seem to occur when calves are near a week of age and older. The morbidity (number of sick calves) ranges from one to two percent up to 20-30 percent. Mortality rates are quite variable. Many calves will recover if treated early. Conversely, up to 25 percent losses have been reported, particularly when either corona or rotavirus is compounded by bacteria. Losses of death were consistently associated with pronounced dehydration.

Rotavirus can survive in the calf’s environment for long periods of time therefore each new batch of calves are exposed. Newborn calves are protected against rotavirus infection during the first few days of life by the presence of specific colostral antibodies acting in the intestine. This protection though drops markedly around 3-4d after birth with calves then becoming susceptible.

PROTOZOAN CAUSES OF CALF SCOURS

Cryptosporidium
Cryptosporidium is a protozoan parasite much smaller than coccidia. It has the ability to adhere to the cells which line the small intestine and to damage the microvilli. As a rule, cryptosporidium is detected in combination with coronavirus, rotavirus, and/ or E. coli. Calves infected by cryptosporidium have ranged from one to three weeks in age. Cryptosporidium oocysts are very resistant to environmental conditions and can survive outside the calf for at least 3-4months.

In calves the source of infection is not adults but rather other calves or the environment. The route of infection is faecal-oral with overcrowding and low levels of hygiene predisposing to infection.
IMPORTANT: Cryptosporidiosis is a significant zoonosis and many human cases have been recorded following contact with farm animals. Salmonella is also a potential risk to humans.

Coccodiosis
Coccidiosis is seldom a problem in young calves. However; outbreaks in calves three to four weeks of age and older have been reported. Most outbreaks were associated with stress, poor sanitation, over-crowding, or sudden changes in feed. Some affected calves may exhibit signs of brain damage but tarry or bloody scours are commonly observed.

PREVENTION

Because calf scours result from a combination of non-infectious factors and infectious microorganisms, it is essential to use more than shots and pills in any effort to control scours successfully. There are managerial as well as medical requirements which must be met. They must complement each other. Furthermore, calf scours prevention is a year-round effort, not a set of activities centred only around calving season.

Management Aspects
All facets of management are important. Particular attention should be paid to nutrition, environment, sanitation, and care of the newborn calf.

1. Nutrition.
   The ration of the pregnant female should be balanced in energy, protein, minerals and vitamins. Care should be given to adjust the nutritional requirements during cold, inclement weather and to keep in
   mind that pregnant replacement heifers have not reached their mature size. Particular care must be taken to provide them with sufficient feed energy for maintenance and growth. Failure to meet energy needs will not only result in a weak calf at birth but also contributes to delays in return to oestrus and lowered conception rates.
2. Environment and sanitation.
   Historically, severe outbreaks of scours are associated with bad weather, storms, slush and mud. Weather conditions are unpredictable and beyond our control. We can, however, control the environment in which the calf is born and raised early in life. The newborn calf needs a dry/clean place if we expect it to survive free of scours. Geographic and climatic conditions dictate the type of management needed to ensure decent shelter. Sanitation is just as important as a dry/clean environment. Ideally, provide a special area used only for calving. After the calf is born and has nursed, it should be moved with its dam to a nursing area before being turned to pasture.
3. Attention to the newborn.
   Calving difficulties may weaken the newborn and its dam; the calf may not nurse sufficient colostrum and scour later on. Perhaps the single most important requirement for the newborn calves is to nurse colostrum early in life. The calf must have colostrum during the six to 12 hours (up to 24 hours) immediately after birth. The calf is born without disease protection. Only by absorbing antibodies present in the colostrum will a calf acquire immunity against the various infectious causes of scours.

Colostrum may be saved from dairy cows. Make sure it is from cows vaccinated against infections predominant in your area and attempt to get it from older cows in the dairy herd. Older, vaccinated cows are more likely to have greater antibody levels than young, unvaccinated heifers. Colostrum should be saved from only the first two milking’s. When needed, frozen colostrum should be thawed out slowly; boiling will destroy most of the antibodies. Colostrum may be kept frozen almost indefinitely.

TREATMENT

Treatment of calves for scours is very similar regardless of cause. Treatment should be directed toward correction of the dehydration, acidosis and electrolyte loss. Antibiotic treatment can be given simultaneously with the treatment for dehydration. Dehydration can be overcome with simple fluids given by mouth early in the course of the disease. If dehydration is allowed to continue, intravenous fluid treatment becomes necessary.

The clinical signs of dehydration first occur when the fluid loss reaches five to six percent of the body weight. Fluid loss of eight percent results in depression, sunken eyes, dry skin and a calf will probably be unable to stand. A 12 percent loss of fluids usually results in death. Oral fluids used early in the scouring process have been quite successful. Consult your veterinarian for electrolytes to be given orally. There are dry electrolyte powders available that can be mixed with water for oral administration.

In terms of what antibiotics to use, ideally a faecal sample from a sick calf should be taken and sent to a laboratory by your veterinarian to determine exactly what organism is present and what antibiotics they are susceptible to. If you are having problems with your current treatment not working against scouring calves, you need to contact your local veterinarian sooner rather than later to determine the cause of the problem.

This information sheet is not intended as a substitute for a veterinary consultation. It is recommended that a consultation be arranged with a Veterinarian if you have any concerns with your animal’s health.