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Causes and prevention of beef calf scours

Quick facts

  • 95% of infectious calf scours is caused by rotavirus, coronavirus, or Cryptosporidium.

  • Dehydration is what kills calves, and correcting with supplemental electrolytes is the most crucial part of any treatment protocol.

  • Let scouring calves continue to nurse. Calves need the nutritional value of the milk to help fight off the disease. Make sure to check the dam’s health.

  • To prevent calf scours, use a system-wide approach that includes, cow health, colostrum management, calf nutrition, cleaning and sanitizing and vaccination.

  • See the calf scours treatment decision tree to help you determine your best course of action.

Calf scours can be a major problem for any cow-calf operation. Controlling the disease is a complex issue and has many variables. While we can identify specific agents of disease that cause scours, it is important to remember that the control of the disease often requires a system-wide approach to prevention rather than individual treatment to solve the problem.

What causes calf scours?

Scours has many causes. We often focus on the infectious causes, which are significant, but it is important to note that there are also non-infectious causes of calf scours. 

Infectious causes

Rotavirus, coronavirus, or Cryptosporidium cause 95% of infectious calf scours cases in calves under 3 weeks of age. These three agents can also be present in combination. All calves are exposed to these pathogens; it is unavoidable. The deciding factor in whether or not a calf gets sick is often dose-dependent, meaning the more pathogen a calf receives, the more likely they are to have scours. 

  • Rotavirus infects cells essential to the absorption of nutrients in the small intestine. The lack of small intestine nutrient absorption causes nutritional deficiencies for the calf and interferes with the rest of the digestive tract’s ability to absorb water. The result is diarrhea, with an added complication of missing nutrients for the calf. 
  • Coronavirus infects cells in a similar way to rotavirus. However, instead of just interfering with absorption, the virus actively kills cells in the lining of the intestine. The result is widespread destruction of the lining of the small intestine. The calf cannot absorb any nutrients, the inflammation is massive, and severe diarrhea occurs.
  • Cryptosporidium, often referred to as 'Crypto', is a protozoan. Protozoa are microscopic animals. The most important thing to remember is that Crypto is not bacteria. Crypto implants itself in the wall of the intestine and causes severe inflammatory damage to the lining of the intestine. This damage results in diarrhea for the calf. Crypto infections are incredibly painful for the calf. Outside of the body, crypto has a thick shell that allows it to survive for long periods in the environment.

Non-infectious causes

Inadequate nutrition

Calves need to eat. They are trying to grow in addition to fighting off any pathogens that could be present. To gain weight and still have the energy to provide an adequate immune system, calves must have energy stored in the form of fat. With beef calves, infectious agents are likely to blame, but you should also check on the dam to make sure she is providing enough milk. Mastitis, big teats, low milk production and poor maternal instinct (calf rejection) are all potential causes of inadequate nutrition that could lead to scours.

How to diagnose scours

Check manure consistency

Just like any mammal ingesting a primarily liquid diet (like human infants), a calf's feces should not be solid. Scours is not defined as loose feces. A calf's feces should be slightly loose. 

  • Normal calf manure should be semi-formed to loose and sit on top of straw bedding. 

  • Scours manure will have a watery consistency and will run immediately through straw bedding. 

  • Unless the manure has blood in it, the color of the manure usually has little to no diagnostic value.

Examine the calf 

A visual and physical exam, in combination with manure consistency, can help you put the pieces together.

  • Visually, the calf should be bright and alert with clear eyes and upright ears. Sick calves are depressed and lethargic, with droopy ears and dull eyes.
  • Watch for calves that remain lying down when most other calves have stood up.
  • Not eating can also be a sign of a sick calf, but the goal should be to pick out the calf that is struggling before they have stopped eating.

Many calves with scours will breathe faster than usual with increased effort. Make sure you are not misdiagnosing scours cases as respiratory infections.

How to treat scours

As with almost anything on a farm, prevention is preferable to treatment. Having treatment protocols is essential for proper calf care, but the primary goal is always to identify the root of the problem and prevent scours. Even with excellent prevention in place, scours cases will occur. Here are the things to consider when treating.

If the calf is unable to stand, call your veterinarian. The calf may need IV fluid therapy in addition to the treatments below.


Dehydration is what kills calves, and correcting it with supplemental electrolytes is the most crucial part of any treatment protocol. Electrolyte feeding should be given in addition to milk feedings. If you can, leave the calf with its mother whenever possible. Work with your veterinarian to decide what electrolytes to use and how often to treat.

  • If you are bottle feeding, DO NOT stop feeding the calf milk. Leave the calf with the dam whenever possible and monitor the calf to ensure it continues drinking milk. The calf needs the nutritional value of the milk to help fight off the disease. 

  • Always mix electrolytes according to package instructions. Feeding electrolytes that are too concentrated can make things worse by causing more scours. 

Pain or discomfort

Scours is extremely uncomfortable and painful for calves. There are several options for anti-inflammatory use in calves. Providing pain relief helps calves get back on their feet faster. Work with your veterinarian to determine what and how much to use. 


As discussed above, 95% of scours cases are not caused by bacteria, meaning in 95% of cases, antibiotics will not treat the cause of the disease. Scours can result in secondary bacterial infections. The only way to know if antibiotics are necessary is to examine the calf. 

  • Every exam should include a rectal temperature. 

  • Use antibiotics in a set protocol you develop with your veterinarian. 

  • Consider using a long-acting antibiotic (8+ days) to prevent secondary infection.

How to prevent calf scours

The cow

Preventing calf scours starts even before the calf is born. A healthy cow produces a healthy calf. We can influence the health of the calf by making sure the cow has a proper body condition score, adequate nutrition (including minerals), and a clean, dry environment. We can also use vaccines to influence what antibodies a cow puts into her colostrum (first milk) that are then passed to the calf. By vaccinating at the correct time while the cow is pregnant, we can improve the quality of the colostrum and target specific scours-causing pathogens. Work with your veterinarian to develop a vaccine protocol.


A calf should drink good quality, clean colostrum within the first two hours of life. Every hour after birth, the calf’s ability to absorb the protective antibodies in colostrum decreases. Receiving colostrum is the single biggest predictor of calf survival and health. Make sure you have some colostrum replacer on hand during calving season. If a calf is unable to drink colostrum from the dam, feed a replacer. If you are unsure if the calf drank colostrum from the dam, feed a replacer. 

Calving area

Exposure to scours-causing pathogens starts the moment the calf is on the ground. If the calving area is not clean and dry, exposure to pathogens is more likely. Make sure your cows are calving in a clean environment. Mud is your biggest enemy. If you cannot avoid mud in your current system, you need to change your system or change the time of year you start calving.

Pathogen build-up

In general, scours-causing pathogens transfer from older animals to younger animals. Additionally, many of the pathogens (especially Cryptosporidium), persist in the environment for an extended period. This means that, over time, disease-causing organisms can build up in an area making exposure and disease more likely for calves. 

  • A 45-60 day calving period (calving window) keeps a large majority of calves the same age within a system that minimizes disease transfer between calf age groups.

  • Sorting and separating cows by calving date can minimize disease transfer between calf age groups.

  • Designating a pasture, concrete pen, or barn for calving and minimizing cattle traffic at all other times of the year can prevent pathogens from building up.


In order of importance, vaccines given to calves are at the bottom of the list. Colostrum, nutrition, clean environment and cow health are all more critical factors. There are products when given at birth under label instructions that can reduce scours, but they are not a cure-all solution. Work with your veterinarian to develop a vaccination protocol.

Author: Joe Armstrong, DVM, Extension educator

Reviewed in 2023

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