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Causes and prevention of dairy 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.

  • DO NOT prevent scouring calves from nursing. Calves need the nutritional value of the milk to help fight off the disease.

  • In general, feed calves a minimum of 8 quarts (2 gallons) per day of either whole milk or high-quality milk replacer (26:20).

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

What is calf scours?

Plain and simple, scours is diarrhea. The cattle industry has routinely used the term scours to refer to diarrhea in young animals for as long as anyone can remember. Scours causes dehydration in calves and is the leading cause of death in calves under one month of age. 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 of 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

Poor nutrition is the most common cause of scours. 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. Not feeding enough milk to give the calf the energy it needs to maintain a healthy immune system is the number one cause of scours.

Incorrect timing

Feed calves on a regular schedule. Feeding at inconsistent times causes calf stress and increases the chance of acidosis.

Incorrect temperature

Calves should be drinking body temperature milk. A cow’s body temperature is between 101 F and 102.5 F.

Incorrect mixing

Make sure to accurately measure water and measure replacer powder by weight, then mix thoroughly. Milk replacer that is too concentrated can cause water from the calf’s body to move into the intestine, resulting in osmotic diarrhea.

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 calves 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 consistency close to water 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 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 mom 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 make sure it is continuing to drink 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. 

  • Antibiotics are usually reserved for when a temperature is too high (above 102.5 F) or too low (below 101 F).

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.


Four quarts of good quality, clean colostrum should be fed within the first two hours of life. Every hour after birth, the calf’s ability to absorb the protective antibodies in colostrum decreases. Managing colostrum correctly is probably the single most influential thing a farmer can do to improve calf health. 

Calving pen

Exposure to pathogens starts the moment the calf is on the ground. If the calving pen is not clean and dry, the exposure to pathogens is more likely. Make sure your cows are calving in a clean environment.

Clean, clean, clean

In addition to a clean calving pen, everything else the calf comes into contact with needs to be clean. As discussed earlier, infectious causes of scours are dose-dependent. More harmful bugs means a higher likelihood of disease. Look at your calf housing and decide what the calves can reach with their mouths. If they can reach it, they will chew on it, and you need to clean it.

  • Clean and disinfect Individual calf housing between each calf use. Clean and disinfect group housing between groups. 

  • Feeding equipment should also be cleaned and disinfected regularly. 

  • Chlorine dioxide is an excellent disinfectant and can be mixed in varying concentrations for different applications.


Calves need to eat because they need calories. The energy need only increases when cold weather is also a factor. Inadequate nutrition leads to sick calves that do not grow. In general, feed calves a minimum of 8 quarts (2 gallons) per day of either whole milk or high-quality milk replacer (26:20).


Timing, mixing and temperature have huge impacts on scours prevention. You should strive to deliver the same product at the same time every day to your calves. Timing and temperature are more straightforward measurements to keep consistent. When mixing milk replacer or when using whole milk, the products can change from day-to-day. 

  • When using milk replacer, weigh all measurements of powder. Humidity, clumping and other factors make the volume an inconsistent measure for a powdered product. 

  • You can measure total solids of your final mixture, or whole milk, to target a consistent reading. 


In the order of importance, vaccines given to calves are towards the bottom of the list. Colostrum, nutrition, clean environment, cow health and feeding consistency are all more critical factors. There are products that can reduce scours when given at birth under label instructions, 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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