Calf laying down in stall
Updated: June 21, 2022
By Sarah Potts

Troubleshooting Calf Scours

Diarrhea, also known as scours, is the number one leading illness in dairy calves (respiratory infection is number two). Scours can lead dehydration, which, if severe, can lead to death in a hurry if the calf does not receive treatment. According to a recent USDA report, 34% of dairy calves experience illness during the pre-weaning period and of those, over half experience scours. Nationally, the average pre-weaning calf mortality rate is 5%, with nearly one third of those deaths associated with scours. Needless to say, calf scours is a universal challenge that has substantial economic impact on dairies across the nation.

The Culprit

Scours can have infectious or noninfectious causes. Infectious scours is caused by bacteria (E. coli, Salmonella spp., or Clostridium), viruses (rotavirus, coronavirus), or protozoa (coccidia, cryptosporidia) and can be transmitted between animals (and sometimes people). Noninfectious scours can be cause by poor nutrition, sub-par milk feeding management, and poor colostrum management. Symptoms of scours includes loose manure that does not sit on top of straw bedding, bloody manure, dehydration, poor appetite, and fever (>102.5°F). Many times, the first noticeable symptom of scours (or other illness) is depressed appetite.

“Calves scouring within the first few days of life could indicate an issue related to calving area sanitation.”


Focal point

  • Scours can have infectious or non-infectious causes
  • Timing of scours onset can narrow down the list of potential pathogens
    • Helps with development of prevention strategies
  • Treat scouring calves with electrolyte solution to prevent dehydration
    • Do NOT substitute electrolytes for a milk feeding
    • AntAibiotics are often not needed


It can be frustrating when trying to determine the root cause of calf scours. Taking note of the age at which calves begin to experience scours symptoms can be extremely helpful when trying to pinpoint an infectious cause. If scours appears in calves less than 48 hours old, E. coli or rotavirus could be to blame. If calves are less than 7 days old, then E. coli, rotavirus, or coronavirus are possible culprits. Coronavirus, Salmonella, clostridia, cryptosporidia, and coccidia often affect calves between 1 and 2 weeks of age, while calves who are over 2 weeks of age are more likely to be affected by Salmonella, clostridia, cryptosporidia, or coccidia. A fecal culture can also help clearly define which (if any) infectious agent is causing scours. This can be extremely helpful when determining course of treatment and identify effective preventative strategies. If an infectious agent cannot be pinpointed, it is also important to consider the possibility of noninfectious causes of scours.

Table 1. Potential scours pathogens according to scours onset.

Age at Onset Potential Pathogen
0-48 hours E. Coli, rotavirus
1-7 days E. Coli, rotavirus, coronavirus
1-2 weeks Coronavirus, Salmonella, clostridia, cryptosporidia, coccidia
>2 weeks Salmonella, clostridia, cryptosporidia, coccidia


The trouble with scours is not the diarrhea itself, but the dehydration that it causes. In most cases, providing scouring calves with oral electrolytes can help mitigate dehydration. When providing oral electrolytes, it is important to follow product mixing instructions. Using too little water can make the solution too concentrated and make scours worse. It is also important to continue offering milk or milk replacer as part of the normal feeding routine. In other words, do not substitute an electrolyte dose for a milk or milk replacer feeding. While they may not drink all of their milk feeding, it should still be offered because proper nutrition can help calves recover quicker. Antibiotics are often not needed to treat scours, but if it coincides with a fever (>103°F), antibiotic treatment may be recommended, so be sure to consult your veterinarian.


Prevention is the best course of action when it comes to managing calf scours. Maintaining a clean, dry, and well-ventilated environment is certainly an important part of scours mitigation. This applies not only to calf housing, but also to calving areas. Calves scouring within the first few days of life could indicate an issue related to calving area sanitation. To prevent pathogen transfer among calves, be sure to clean all feeding equipment, such as bottles or buckets, in between calves. Feeding older calves before younger calves and any sick calves last can also help reduce the potential for transferring infectious agents between calves. Finally, always be sure to clean individual calf housing, such as pens or hutches, in between calves.

Good colostrum management is also critical for developing the calf’s immune system.  Colostrum management can be evaluated by examining colostrum quality before feeding using a Brix refractometer or colostrometer.  As a rule of thumb, a Brix reading of >22% or a colostrometer reading of >50 g IgG/L is indicative of good quality colostrum.  Calves should receive 10% of their body weight of good quality colostrum within the first 12 hours of life.  Ideally, this would be split into two feedings, with the first occurring within 2-4 hours of birth and the second at 12 hours after birth.  Colostrum effectiveness can be evaluated by taking a blood sample from calves between 2 to 7 days of age and assessing serum total protein levels.  On-farm, a Brix refractometer can be used for this and a serum total protein >15 g/L suggests good passive transfer of immunity.  

Milk feeding management is also plays a role in scours prevention.  Because calves thrive on consistency, be sure to follow a routine feeding schedule each day.  It is also important to follow milk replacer mixing instructions to ensure proper solids content.  Feeding milk replacer that is too concentrated (not enough water added) or too dilute (too much water added) can cause scours.  Ideally, milk replacer should be mixed to contain 12-13% solids, which can be evaluated on farm using a Brix refractometer.

Vaccinations can also play a role in scours prevention.  Vaccinating dry cows 2-6 weeks before calving can boost colostrum antibody concentrations for specific infectious agents.  These dry cow vaccines can help reduce calf hood incidence of E. coli, coronavirus, and rotavirus. 


Scours is an inevitable part of rearing dairy calves. However, monitoring colostrum management, utilizing good sanitation practices, ensuring good milk feeding practices, and adopting a dry cow vaccination program are all tools that can be used to help prevent and reduce the economic impact of scours.

This article appears on June 16, 2022, Volume 3, Issue 2 of the Maryland Milk Moos newsletter.

Maryland Milk Moo's, June 16, 2022, Vol.3, Issue 2

Maryland Milk Moos is a quarterly newsletter published by the University of Maryland Extension that focuses on dairy topics related to Nutrition and Production, Herd Management, and Forage Production. To subscribe to this newsletter, click the button below to enter your contact information.