Getting to the Bottom of Calf Scour
Calf scour听remains听one of the most common and costly health challenges in beef听suckler听herds across Scotland. While mortality is the most visible impact, the hidden costs are often greater. Calves that experience significant diarrhoea in the first weeks of life听frequently听suffer reduced growth rates and lower sale weights later in the season. For spring-calving suckler herds in particular, scour can quickly escalate during busy periods when labour is already stretched.听
Scour is not a single disease but a clinical sign with multiple infectious causes. In Scottish beef calves, the most common pathogens include听Rotavirus,听Coronavirus, enterotoxigenic听E. coli听K99,听Cryptosporidium parvum, and Salmonella species such as听Salmonella Dublin听and听Salmonella Typhimurium.听Identifying听which pathogen is involved is important, as age of onset, severity and control strategies differ.听
Which pathogen is to blame?听
Enterotoxigenic听E. coli听K99 typically affects calves within the first few days of life. It attaches to the intestinal lining using fimbriae (the K99 antigen) and produces toxins that cause rapid fluid loss. When scour appears in calves under three days old, inadequate colostrum intake or heavy contamination of calving pens is often the underlying issue.听
Rotavirus and coronavirus are most common between five and fourteen days of age. These viruses damage the gut lining, reducing the calf鈥檚 ability to absorb nutrients and fluids. While many calves recover with supportive treatment, disease severity increases when environmental contamination is high or when colostrum intake has been suboptimal.听
Cryptosporidium parvum听is highly infectious, resistant to many disinfectants and capable of surviving for prolonged periods in damp bedding. Group calving indoors, particularly during wet Scottish springs, increases infection pressure significantly.听
Salmonella differs from the other scour pathogens because it听frequently听causes systemic illness. Affected calves are often dull,听febrile听and reluctant to suck before scour develops.听Bloody diarrhoea听may occur. Some strains, particularly听S. Dublin, can create carrier animals and cause disease in adult cows, including abortions. Salmonella is also zoonotic, posing a risk to farm staff and family members. Laboratory testing and speciation are important, as听identifying听the serotype helps听determine听likely persistence, vaccination听options听and public health risk.听
How to deal with scour听
Regardless of the pathogen involved, calves do not die from diarrhoea itself but from dehydration and metabolic acidosis. Prompt fluid therapy is therefore the cornerstone of treatment. Oral electrolyte solutions should be given in addition to continued milk intake from the dam whenever possible. Removing milk entirely can reduce energy supply and delay recovery. Antibiotics are not听indicated听for viral or Cryptosporidium infections but are听appropriate in听cases of systemic illness, particularly when Salmonella is suspected.听
Prevention, however,听remains听far more effective than treatment. Colostrum management is the single most听important factor influencing calf health. Unlike dairy systems where feeding can be controlled directly, suckler calves depend on early and vigorous suckling. Observing calving's where possible, ensuring calves stand promptly and听assisting听weak calves to suck can significantly improve immunity. Research consistently shows that calves receiving adequate high-quality colostrum within the first two hours of life have reduced incidence and severity of scour.听
Dam vaccination during late pregnancy can increase antibody levels in colostrum against rotavirus,听coronavirus听and听E. coli听K99. In herds with confirmed Salmonella, vaccination may also reduce shedding and improve calf protection. However, vaccination cannot compensate for poor calving hygiene or inadequate colostrum intake.听
Environmental management is particularly important in beef systems where calving often occurs in group pens or straw-bedded courts. High stocking density, wet听bedding听and continuous use of calving areas allow pathogens to accumulate rapidly. Regular bedding replacement, ensuring dry lying areas and avoiding overcrowding are practical measures that significantly reduce infection pressure. Where possible, rotating or resting calving pens between batches can help break disease cycles.听
Scour outbreaks rarely arise from a single failure. More often, they reflect a combination of high pathogen challenge and insufficient immunity. Beef herds that consistently achieve good calf health focus on optimising colostrum intake while minimising environmental contamination during the critical first weeks of life.听
Top tips听
- Ensure every calf suckles within two hours of birth听
- Assist听weak calves promptly and听monitor听first feeds听
- Consider late-gestation vaccination to boost听colostral听antibodies听
- Keep calving areas clean, well-bedded and uncrowded听
- Replace wet bedding regularly during busy periods听
- Provide oral electrolytes early and continue milk intake听
- Practise good hygiene when handling sick calves due to zoonotic risk听
Strong colostrum management, clean calving听environments听and听early action听remain the foundations of scour control in beef herds. Small improvements applied consistently can yield significant gains in calf survival,听growth听and overall herd performance.听
Captiva听Mills, Consultant,听Captiva.Mills@sac.co.uk
Posted by SAC Consulting on 16/03/2026
