Dr. Brad Heins
Diarrhea and other digestive diseases are some 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 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
In young calves, the most common causes of scours are either viruses and/or bacteria although as the calf ages, it is also susceptible to coccidia and other parasites. With an unprimed immune system, the calf is often infected from the environment or even directly from the cow by nursing contaminated teats. Viruses such as rotavirus and coronavirus often infect the animal in the first few days of life and may cause clinical symptoms of diarrhea due to blunting or destruction of the cells lining the intestine which leads to reduced nutrient absorption. Bovine viral diarrhea virus (BVD) may also affect neonatal calves, leading to diarrhea, oral lesions, hemorrhage and increased risk of persistently infected animals being born. 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 due to toxin production that increases fluid movement into the intestines while others may be linked to bloody scours of variable severity. Whether or not infection with these bacteria leads to diarrhea is dependent on environment and management factors. Several parasitic agents may also be responsible for causing calf diarrhea including Cryptosporidium and Coccidia species in young calves and intestinal nematodes as the animal ages. These organisms are shed by the adults within the herd and can 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 after birth. Colostrum is the milk produced by the cow or heifer and is available for only a short period after calving. In order for the cow to produce adequate colostrum, she must be in a positive energy balance with a diet containing an appropriate amount of energy and protein. Additionally, pre-calving vaccinations can increase immunoglobulin production in the colostrum to provide better protection for the calf. It contains a higher concentration 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. 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 as 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. It is also important that managers ensure the cow or heifer does not reject the calf. In these situations, or 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.
Calves at Risk of Poor Colostrum Consumption
Calves born to heifers represent a significant area of concern as beef heifers may have lower volume and/or 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”. Calves experiencing failure of passive transfer are at increased risk of digestive and respiratory disease. Calves experiencing dystocia at birth or those 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. Additionally, cows with large sagging udders or those with poor teat conformation may limit the ability of the calf to adequately nurse, or have a greater risk of mastitis, all of which will limit consumption and absorption of an adequate volume of colostrum from the cow.
Colostrum Products
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) in a single dose, 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. There are also two main methods of manufacturing colostrum products; one method is collection of plasma derived immunoglobulins that are mixed with a milk-based powder and the other method is a dehydrated colostrum product that can be mixed with water and dosed to the calf. 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, 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 destroy many of the valuable antibodies we are trying to provide. The colostrum should be administered by bottle and nipple if possible, but in calves that do not suckle, one way to guarantee the calf receives an adequate amount of the colostrum substitute is to use an esophageal feeder to provide the feeding, 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 3 months prior to moving in cows nearing their delivery dates to minimize 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 that cows and older calves may have begun to shed. 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 and reduced organic matter contaminating the udder.
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, have lost weight or are failing to thrive, or have a wet or manure covered tail. While some people may claim to be able to distinguish which agent is responsible for the disease based on the color or odor of the feces, it is important to submit appropriate diagnostic samples whenever possible so that correct therapy can be provided as well as potential management changes. In general, fecal floatation samples may be used to identify some organisms such as parasites but are very poor samples for diagnosing viruses and bacteria which may require advanced diagnostics such as culture or molecular PCR detection. 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 and may lead to a misdiagnosis. 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.
When determining if a calf should be treated for diarrhea, I often follow a few simple criteria:
- How difficult was the calf to catch? If you had to chase it down with a 4-wheeler or UTV, the calf probably requires monitoring and not intensive therapy, but if the calf is down or slow to move, the calf probably requires oral fluid therapy and potentially IV fluids.
- Is the calf’s flank sunken? If so, this indicates the calf has not had a recent meal and should be evaluated.
- Are the ears droopy and eyes recessed? For each millimeter of eye recession, the calf is experiencing approximately 2% dehydration; i.e. if the eyes are recessed 4 mm, then the calf is 8% dehydrated and in need of aggressive fluid therapy.
- Is there prolonged skin tent when the skin over the neck is pulled away with your fingers? As the calf becomes dehydrated, the skin loses hydration and becomes less turgid leading to skin staying tented for > 2 seconds.
- Does the calf have a suckle reflex? For calves that were growing well, the loss of suckle reflex indicates the presence of dehydration, energy loss, and acidosis due to lactic acid buildup in the body.
Much of the treatment for calf scours involves supportive care to ensure the animal has adequate access to milk and water and is not becoming dehydrated. 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 to prevent the loss of the calf and keep in mind that until the diarrhea resolves, the calf will require ongoing fluid therapy to replace excess fluid losses. Ideally, oral electrolyte solutions will contain a buffer to reduce acidosis, appropriate electrolyte levels to aid with ongoing electrolyte losses, and even an energy source to support calf metabolism. In some cases, using a dose of colostrum supplement or replacer can help provide antibodies that may act locally within the intestines to help bind pathogens. Remember that if the intestinal epithelium was damaged, it will also take time for the cells to be replaced and digestion to become normal.
The typical response to outbreaks of neonatal diarrhea is to give antibiotics. However, many of the causes of diarrhea are not bacterial or are self-limiting so it should not be surprising that many times antibiotic treatment is not effective. Guidance from your herd veterinarian should be used in all cases when treating neonatal calves to ensure appropriate antimicrobial therapy, 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.
As with all herd health problems, the herd veterinarian should be consulted whenever possible to ensure appropriate diagnostics and therapy are provided. It may not always be possible to save every calf, but with improved management, producers may reduce the losses associated with calf scours.