Calf Scours and Infectious Identification Back »

Written collaboratively by Kaylee Wegner and David Casper.

Scours tend to be the first disease to impact calves on the dairy operation, which can have a lifelong implications. Reduced feed intake and large amounts of lost fluids due to scouring can impair growth early in life and affect lifetime productivity. The impairments in growth can result in slower growth rates, poorer feed conversions, later breeding and future lower milk production. Obviously, if the scours, diarrhea, and subsequent dehydration are severe enough, the life of the calf can be lost. Preventing scours and keeping calves hydrated when disease strikes on the dairy operation reduces the impact of sickness on performance of the dairy herd.

About Scours

Scours are a calf’s response to a metabolic upset or imbalance in the digestive tract causing changes in the visual appearance of manure, water, mucous, and occasional blood in the stools of calves. Usually, we typically believe that the diarrhea is being caused by bacterial scours, but scours can occur as a result of a nutritional change or imbalance. Overfeeding whole milk, sudden changes to the diet, feeding less than 10% or greater than 18% solids in milk replacer, water quality for drinking and/or reconstituting milk replacers, and feeding poor quality milk replacers can all be causes of loose stools. It is important to consider these non-infectious causes of diarrhea before treating a calf for scours because antibiotics will not help in these situations.


Scours can also be caused by a number of infectious agents or pathogens, which can infect the calf during the first few weeks of life depending on a number of factors on the dairy operation. Table 1 outlines the common or typical causes of scours. The differences in a calf’s age and color of the scours can help identify the specific type of infection or pathogen causing the scours. Proper steps can be taken to eliminate the infectious agent once the correct cause is identified.

Table 1. Scours caused by different infectious agents will occur at different stages of a calf's life. Disease onset combined with different signs of infection can be useful in identifying the cause of scours.

commonly affected

E. coli
24-36 hours
diarrhea, depression, and coma
> 6 days old
diarrhea with blood and fibrin in the feces, depression, and fever.
< 2 weeks
None in most cases; may include listlessness, uneasiness or strain, kicking at abdomen, foul smelling diarrhea that contains blood.
1-2 weeks
Watery brown to light green scours that contain blood and mucus.
3 days - 3 weeks
Profuse, watery and yellow diarrhea.
7-10 days
Erosions and ulcers on the tongue, lips, and mouth. Very liquid feces that are yellowish brown to grayish green which may become yellowish gray and contain blood and fibrin as the disease progresses.
Eimeria bovis/ Eimeria zeurnii
> 21 days
Tarry and often bloody scours.
2-3 weeks
Watery brown to light green feces with blood and mucus.


Because of the early onset of scours, prevention is more effective in controlling scours than treating sick calves. Scours caused by most infectious agents are best prevented by early feeding of high quality colostrum and ensuring the calving area is clean, dry, and well-bedded. Proper sanitation of maternity pens and calf housing are important in controlling bacterial proliferation. Veterinarian prescribed vaccination protocols for cows during the dry period can minimize the number of cases of bovine virus diarrhea (BVD), rotavirus, and coronavirus by providing antibodies in the colostrum.

Loose stools caused by scours cause calves to become quickly dehydrated. The reason is most of the water consumed by the calf is quickly excreted. The greatest damage to the health of the calf is caused by dehydration, rather than the agent which caused the scours. Ensuring that all, especially scouring calves, have ready access to ample clean water is especially important during this time. Along with water loss, calves also lose electrolytes and other essential fluids. Electrolyte supplementation can make the difference between calves that recover from scours quickly and those that continue to be poor doers up to and when they enter the milking herd.

Understanding the signs of different non-infectious and infectious agents that cause loose stools in calves is the first step in identifying the cause of scours and taking the appropriate response. Prevention of infection through clean and sanitary facilities and equipment is instrumental in reducing the incident of scours. When calves do become infected, proper hydration and electrolyte therapy will aid the calf in responding as the disease runs its course. Calves are the foundation for the future milking herd; taking a few extra steps to reduce the incidence and severity of scours can result in healthier cows in the long-run.

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