By: Dr. Bradley D. Heins, DVM, MFAM Candidate and
Dr. Roger W. Ellis. MS, DVM University of Georgia College of Veterinary Medicine, Dept. of Population Health

Diarrhea and other digestive diseases are one of the most common causes of death loss and morbidity in beef and dairy herds in the United States. With a variety of viruses, bacteria, and parasites capable of causing disease, it is difficult to accurately identify the organism responsible for the disease, even if diagnostic samples are submitted for analysis. This occasionally limits our ability as producers and veterinarians to adequately respond to an outbreak and reduce or eliminate the problem. As with many other diseases, prevention is often the best course to take to limit the exposure of our animals and reduce the risk of disease in the herd and the subsequent risk of death and lost production of those animals affected.

Causes of Scours

Young calves are the most susceptible to many of the scours-causing viruses and bacteria. With an unprimed immune system, the calf is often infected from the environment or from the cow. Viruses such as rotavirus and coronavirus often infect the animal in the first few days of life and may cause clinical symp- toms of diarrhea due to destruction of the cells lining the intestine which leads to malabsorption of nutrients. Bovine viral diarrhea virus (BVD) may also affect neonatal calves, leading to diarrhea, oral lesions, hemorrhage and death. Disease due to BVD may be more common if persistently infected animals are found within the herd as the high level of shedding represents a significant risk factor for neonatal diarrhea. Many of the bacterial agents responsible for scours are commonly isolated in the environment and carrier adult animals within the herd. The primary bacterial agents responsible include E. coli, Salmonella, and Clostridium species. Some E. coli species may cause a profuse watery diarrhea while others may be linked to bloody scours of variable severity.

Whether or not these bacteria actually cause diarrhea is dependent on environment and management factors. A number of parasitic agents may also be responsible for causing calf diarrhea including Cryptosporidium and Coccidia species. These organisms are shed by the adults within the herd and are able to infect the calves through dirty equipment and contaminated environments.

Protection from Colostrum

One of the best ways to prevent scours in calves is to ensure each calf receives an adequate amount of colostrum delivered in a timely manner. Colostrum is the milk produced by the cow or heifer available shortly after calving. It contains a higher concentra- tion of maternal antibodies and increased fat and protein content when compared to the regular milk produced. Colostrum in beef cows is often more concentrated than that from dairy animals, but one way to boost colostral antibodies is to vaccinate the cow four to six weeks before anticipated parturition. From a management standpoint, it is essential that the beef calf rises to nurse the cow within the first two or three hours after birth. It is also important that managers ensure the cow or heifer does not reject the calf. In situations where the cow does not have sufficient colostrum, a colostrum replacer may be used to drench the calf to provide an adequate volume of antibodies that may help to limit early infection. Shortly after birth, the calf begins to lose the ability to adequately absorb the antibodies from the colostrum, making it less effective at preventing disease.

Calves born to heifers represent a significant area of concern as beef heifers may have lower quality of colostrum due to decreased antibody content. Poor quality colostrum or poor absorption of antibodies can result in the calf having a condition termed "failure of passive transfer." Consequently, the affected calves are at increased risk of digestive and respiratory disease. Calves that experience dystocia at birth or are born as twins may have reduced ability to nurse the cow due to being weak, thus it is important to pay close attention to these animals to ensure they have a chance to absorb these early nutrients. Cows with large sagging udders or those with poor teat conformation may limit the ability of the calf to adequately nurse and absorb an adequate volume of colostrum from the cow.

A variety of commercially available colostrum supplements and replacers are available on the market but there is a significant difference between the two product types. Colostrum supplements often only contain 50 grams of immunoglobulin (IgG), the important antibodies responsible for improving calf immunity, while colostrum replacers contain 100 grams or more of IgG. Colostrum replacers also contain many of the fat and protein molecules found in natural colostrum which are important for helping the calf get a good start, especially in cold weather. An additional option would be to collect a gallon of colostrum from a local dairy (keeping in mind farm biosecurity measures) or from any fresh mature cow and freezing it in a zip- top bag and thawing in warm water when needed. If one should choose to use this method, it is important to never use colostrum that has been frozen for more than one year and ensure that the water used to thaw the colostrum is not excessively hot, as that will often destroy the antibodies one are trying to provide. In calves that don't suckle, one way to guarantee the calf receives an adequate amount of the colostrum substitute is to use an esophageal feeder to provide the liquid, taking care not to insert the tube into the trachea which will force liquid into the lungs and lead to calf death.

Pasture Management

One of the easiest ways to reduce pathogen exposure from environmental contamination is to have a dedicated calving area. It is best if cattle are kept out of the calving area for three months prior to moving in cows nearing delivery. This decreases the amount of contamination on the pasture. As the herd progresses through the calving season, animals that have not yet calved may be moved to an additional clean pasture, to further reduce the opportunity for the newborn calves to be exposed to scours causing agents. This method of pasture management was developed in the Great Plains and is known as the "Sandhills Calving System" and has been shown to significantly reduce the risk of neonatal calf diarrhea when compared to calving in regular year-round pasture environment.

Additional pasture management should be used to ensure there is adequate grass or other forage available. Low stocking density, adequate grass cover and length, plus good drainage will help reduce the environmental contamination that often negatively affects calf health and production. Not only will this maintain body condition and milk production in the cow herd, but it will limit the ability of the infectious agents to be transmitted due to increased pasture length.

Scours Diagnosis and Treatment

It may be difficult to distinguish which calf or calves in a herd are suffering from scours, but it is important to look for those animals that may appear clinically sick or to have lost weight, have a wet or manure covered tail, or observe defecation whenever possible. While many people may claim to be able to distinguish which agent is responsible for the disease, it is important to submit appropriate diagnostic samples whenever possible so that correct therapy can be provided. In general, fecal samples may be used to identify some organisms such as the parasites, but are very poor samples for diagnosing viruses and bacteria. If a calf dies on the farm and is to be submitted for diagnostics, it is important to have the samples taken by a veterinarian and submitted within a few hours as other bacterial organisms often overgrow the agents responsible for disease. One critical point is to use disposable gloves when handling scouring calves, as many of the pathogens that infect calves also affect humans, some leading to severe diarrhea, dehydration, septicemia, or even death in rare cases.

Much of the treatment for calf scours involves supportive care to ensure the animal has adequate access to milk and water. The calf should not be removed from the source of nutrients as this provides the best source of energy and electrolytes for the young animal. The primary cause of death in affected animals is usually not the agents themselves, but the dehydration that follows. If necessary, one should consult their veterinarian to provide appropriate oral therapy of electrolytes or intravenous fluid therapy in order to prevent the loss of the calf.

The typical response to out- breaks of neonatal diarrhea is to give antibiotics. However, as one can see many of the causes of diarrheal disease are not bacterial so it isn't surprising that many times antibiotic treatment is not effective. Guidance from the herd veterinarian should be used in all cases when treating neonatal calves to ensure appropriate antimicrobial choice, as well as ensuring that the animal being treated is not severely dehydrated as those individuals often may have reduced ability to clear the antibiotic from the body due to reduced kidney and liver function which may lead to a reduction in survival despite therapy.

A number of other potential products are available to assist with reducing the risk of calf scours including electrolyte solutions, antimicrobial drugs, and vaccines, but as with all herd health problems, the herd veterinarian should be consulted whenever possible to ensure appropriate diagnostics and therapy are provided for each individual situ- ation. It may not always be possible to save every calf, but with improved management, producers may reduce the losses associated with calf scours.

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