1. Introduction
Neonatal calf diarrhoea (“calf scour”) remains one of the leading causes of morbidity, mortality and antibiotic use in dairy and beef youngstock systems worldwide (Animal Health Ireland 2021; Trotz-Williams et al. 2007). Scour is not a single disease, but a clinical outcome resulting from disruption of intestinal function caused by infectious agents, environmental stressors and management factors acting together (Constable et al. 2017).
The pathogens most frequently associated with calf scour include bacteria (Escherichia coli, Clostridium perfringens), viruses (rotavirus, coronavirus) and protozoa (Cryptosporidium parvum, Eimeria spp.). However, exposure alone does not explain disease occurrence. Increasingly, research shows that the environment in which the calf is born and reared determines whether disease develops (Calderón-Amor et al. 2020; NADIS 2023).
2. Most calf scour starts in the environment
Environmental hygiene and housing conditions are consistently identified as dominant risk factors for calf scour.
Case–control and cohort studies show that calves reared in wet, contaminated bedding, poorly drained pens and unhygienic calving environments have a significantly higher incidence of diarrhoea (Klein-Jöbstl et al. 2014; Calderón-Amor et al. 2020). These environments increase pathogen survival and dramatically raise the infectious dose calves are exposed to during their most vulnerable early life (Animal Health Ireland 2021).
Drinking-water hygiene is an often-overlooked component of this environment. Biofilms frequently develop in pipes, troughs and buckets, intermittently releasing pathogens such as E. coli into water supplies (Münster et al. 2024). Poor water quality has been linked to reduced immunity, impaired growth and higher calf mortality (Kamal et al. 2024).
Together, these findings support the principle that most calf scour does not start in the calf – it starts in the environment.
3. Biofilms, ammonia and environmental stress
Biofilms allow microorganisms to persist despite routine cleaning and disinfection. Studies show that conventional disinfectants often fail to penetrate established biofilms, allowing rapid recolonisation of surfaces once cleaning stops (Münster et al. 2024).
At the same time, excessive microbial breakdown of organic matter in bedding and on floors drives ammonia production. Although ammonia is best known for its respiratory effects, it is also a reliable indicator of poor environmental biological balance and excessive pathogen pressure (Calderón-Amor et al. 2020).
Chronic environmental stress weakens calves’ natural defence mechanisms, including gut barrier integrity and mucosal function, making it easier for enteric pathogens to attach, colonise and damage the intestinal lining (Constable et al. 2017; NADIS 2023).
4. Protozoa: the overlooked driver of calf scour
Protozoal pathogens, particularly Cryptosporidium parvum and Eimeria spp., are a major but frequently underestimated cause of calf scour.
Cryptosporidium parvum commonly affects calves between 5 and 21 days of age and causes severe villus atrophy, malabsorption and watery diarrhoea (Thomson et al. 2017). Importantly, protozoal oocysts are extremely resistant to commonly used disinfectants, including chlorine and many oxidising agents (Robertson et al. 2014; Ryan et al. 2021).
Oocysts can survive for months in:
- Moist bedding
- Soiled floors
- Calf pens
- Drinking systems and equipment
As a result, the environment becomes the primary reservoir of infection, not the calf (Thomson et al. 2017). There is no broadly effective curative treatment for cryptosporidiosis; control relies almost entirely on environmental management and reduction of exposure (Animal Health Ireland 2021).
5. Why antibiotics and disinfectants alone fall short
Antibiotics do not address dehydration, do not repair intestinal damage and are ineffective against viral and protozoal causes of scour. Furthermore, repeated antibiotic use contributes to antimicrobial resistance, a major One Health concern (WHO 2020).
Similarly, repeated chemical disinfection without addressing underlying biofilm and environmental biology often leads to rapid pathogen rebound. This “clean–dirty cycle” leaves calves repeatedly exposed during early life (Münster et al. 2024).
6. How Pruex helps: fixing the environment first
Pruex takes an environment-first approach by guiding microbial ecology toward stability rather than sterility.
Using selected beneficial Bacterial species, Pruex works by:
- Establishing positive biofilms in water systems, reducing pathogen-dominated biofilm formation on troughs and pipes
- Improving bedding and floor biology, slowing the breakdown of organic matter into ammonia-producing compounds
- Creating drier, less pathogenic conditions that limit protozoal persistence
- Reducing environmental stress so calves can maintain gut integrity and immune competence
The concept of managing surfaces to favour beneficial, non-infective microbial communities is increasingly recognised as a sustainable disease-prevention strategy in livestock systems (Bastos et al. 2022).
7. Environmental health, calf health and antibiotic reduction
By lowering pathogen pressure in water, bedding and housing environments, calves encounter fewer bacteria, viruses and protozoa during early life.
Studies show that Bacterial detergent based interventions can reduce diarrhoea incidence and improve calf growth, supporting the principle behind Pruex’s approach (Le et al. 2016). Healthier calves require fewer treatments, less labour intervention and reduced antibiotic use, aligning calf performance with antimicrobial stewardship goals (Animal Health Ireland 2021; WHO 2020).
8. Conclusion
Most calf scour does not start in the calf – it starts in the environment. Dirty bedding, biofilm-contaminated water systems, ammonia-rich housing and protozoa-friendly conditions combine to increase pathogen exposure and overwhelm the immature calf gut.
Because key scour agents such as Cryptosporidium are highly resistant to disinfectants, prevention depends on managing the biological environment, not merely reacting once calves are sick. Pruex supports this by restoring microbial balance in water, bedding and floors. When environmental biology is stable, calves are more resilient, scour incidence is reduced, and reliance on antibiotics falls.
References
Animal Health Ireland. 2021. Management of the Scouring Calf. AHI, Dublin.
Bastos, C., Faciola, A.P., and Franz, E. 2022. Positive biofilms to guide surface microbial ecology in livestock environments. One Health 14:100386.
Calderón-Amor, J., Gallo, L., Vitali, A., et al. 2020. Dairy calf welfare and factors associated with diarrhea and respiratory disease. Animals 10(11):2070.
Constable, P.D., Hinchcliff, K.W., Done, S.H., and Grünberg, W. 2017. Veterinary Medicine. 11th ed. Elsevier, London.
Kamal, M.A., Rashad, A.M., and El-Sayed, A. 2024. Effect of drinking water quality on immunity and mortality in dairy calves. Archives of Animal Breeding 67:25–38.
Klein-Jöbstl, D., Iwersen, M., and Drillich, M. 2014. Farm characteristics and calf management practices associated with diarrhea. Journal of Dairy Science 97(8):5110–5119.
Le, O.T., Dart, P.J., Harper, K., et al. 2016. Effect of probiotic Bacillus amyloliquefaciens H57 on diarrhoea in dairy calves. Animal Production Science 56:1990–1998.
Münster, P., Heitmann, S., and Truyen, U. 2024. Drinking-water biofilm development in livestock systems. Frontiers in Animal Science 5:1467287.
NADIS. 2023. Calf Scour in Beef and Dairy Rearing Units. NADIS, UK.
Robertson, L.J., Björkman, C., Axén, C., and Fayer, R. 2014. Cryptosporidiosis in farmed animals. Parasitology 141:1455–1475.
Ryan, U., Fayer, R., and Xiao, L. 2021. Cryptosporidium in humans and animals. Clinical Microbiology Reviews 34:e00062-19.
Thomson, S., Hamilton, C.A., Hope, J.C., et al. 2017. Bovine cryptosporidiosis and control strategies. Veterinary Research 48:42.
Trotz-Williams, L.A., Jarvie, B.D., Martin, S.W., et al. 2007. Calf-level risk factors for neonatal diarrhoea. Preventive Veterinary Medicine 82:12–28.
World Health Organization. 2020. Antimicrobial Resistance. WHO,
Calf Scour: Why It Starts in the Environment – and How Pruex Can Help
1. Introduction
Neonatal calf diarrhoea (“calf scour”) remains one of the leading causes of morbidity, mortality and antibiotic use in dairy and beef youngstock systems worldwide (Animal Health Ireland 2021; Trotz-Williams et al. 2007). Scour is not a single disease, but a clinical outcome resulting from disruption of intestinal function caused by infectious agents, environmental stressors and management factors acting together (Constable et al. 2017).
The pathogens most frequently associated with calf scour include bacteria (Escherichia coli, Clostridium perfringens), viruses (rotavirus, coronavirus) and protozoa (Cryptosporidium parvum, Eimeria spp.). However, exposure alone does not explain disease occurrence. Increasingly, research shows that the environment in which the calf is born and reared determines whether disease develops (Calderón-Amor et al. 2020; NADIS 2023).
2. Most calf scour starts in the environment
Environmental hygiene and housing conditions are consistently identified as dominant risk factors for calf scour.
Case–control and cohort studies show that calves reared in wet, contaminated bedding, poorly drained pens and unhygienic calving environments have a significantly higher incidence of diarrhoea (Klein-Jöbstl et al. 2014; Calderón-Amor et al. 2020). These environments increase pathogen survival and dramatically raise the infectious dose calves are exposed to during their most vulnerable early life (Animal Health Ireland 2021).
Drinking-water hygiene is an often-overlooked component of this environment. Biofilms frequently develop in pipes, troughs and buckets, intermittently releasing pathogens such as E. coli into water supplies (Münster et al. 2024). Poor water quality has been linked to reduced immunity, impaired growth and higher calf mortality (Kamal et al. 2024).
Together, these findings support the principle that most calf scour does not start in the calf – it starts in the environment.
3. Biofilms, ammonia and environmental stress
Biofilms allow microorganisms to persist despite routine cleaning and disinfection. Studies show that conventional disinfectants often fail to penetrate established biofilms, allowing rapid recolonisation of surfaces once cleaning stops (Münster et al. 2024).
At the same time, excessive microbial breakdown of organic matter in bedding and on floors drives ammonia production. Although ammonia is best known for its respiratory effects, it is also a reliable indicator of poor environmental biological balance and excessive pathogen pressure (Calderón-Amor et al. 2020).
Chronic environmental stress weakens calves’ natural defence mechanisms, including gut barrier integrity and mucosal function, making it easier for enteric pathogens to attach, colonise and damage the intestinal lining (Constable et al. 2017; NADIS 2023).
4. Protozoa: the overlooked driver of calf scour
Protozoal pathogens, particularly Cryptosporidium parvum and Eimeria spp., are a major but frequently underestimated cause of calf scour.
Cryptosporidium parvum commonly affects calves between 5 and 21 days of age and causes severe villus atrophy, malabsorption and watery diarrhoea (Thomson et al. 2017). Importantly, protozoal oocysts are extremely resistant to commonly used disinfectants, including chlorine and many oxidising agents (Robertson et al. 2014; Ryan et al. 2021).
Oocysts can survive for months in:
As a result, the environment becomes the primary reservoir of infection, not the calf (Thomson et al. 2017). There is no broadly effective curative treatment for cryptosporidiosis; control relies almost entirely on environmental management and reduction of exposure (Animal Health Ireland 2021).
5. Why antibiotics and disinfectants alone fall short
Antibiotics do not address dehydration, do not repair intestinal damage and are ineffective against viral and protozoal causes of scour. Furthermore, repeated antibiotic use contributes to antimicrobial resistance, a major One Health concern (WHO 2020).
Similarly, repeated chemical disinfection without addressing underlying biofilm and environmental biology often leads to rapid pathogen rebound. This “clean–dirty cycle” leaves calves repeatedly exposed during early life (Münster et al. 2024).
6. How Pruex helps: fixing the environment first
Pruex takes an environment-first approach by guiding microbial ecology toward stability rather than sterility.
Using selected beneficial Bacterial species, Pruex works by:
The concept of managing surfaces to favour beneficial, non-infective microbial communities is increasingly recognised as a sustainable disease-prevention strategy in livestock systems (Bastos et al. 2022).
7. Environmental health, calf health and antibiotic reduction
By lowering pathogen pressure in water, bedding and housing environments, calves encounter fewer bacteria, viruses and protozoa during early life.
Studies show that Bacterial detergent based interventions can reduce diarrhoea incidence and improve calf growth, supporting the principle behind Pruex’s approach (Le et al. 2016). Healthier calves require fewer treatments, less labour intervention and reduced antibiotic use, aligning calf performance with antimicrobial stewardship goals (Animal Health Ireland 2021; WHO 2020).
8. Conclusion
Most calf scour does not start in the calf – it starts in the environment. Dirty bedding, biofilm-contaminated water systems, ammonia-rich housing and protozoa-friendly conditions combine to increase pathogen exposure and overwhelm the immature calf gut.
Because key scour agents such as Cryptosporidium are highly resistant to disinfectants, prevention depends on managing the biological environment, not merely reacting once calves are sick. Pruex supports this by restoring microbial balance in water, bedding and floors. When environmental biology is stable, calves are more resilient, scour incidence is reduced, and reliance on antibiotics falls.
References
Animal Health Ireland. 2021. Management of the Scouring Calf. AHI, Dublin.
Bastos, C., Faciola, A.P., and Franz, E. 2022. Positive biofilms to guide surface microbial ecology in livestock environments. One Health 14:100386.
Calderón-Amor, J., Gallo, L., Vitali, A., et al. 2020. Dairy calf welfare and factors associated with diarrhea and respiratory disease. Animals 10(11):2070.
Constable, P.D., Hinchcliff, K.W., Done, S.H., and Grünberg, W. 2017. Veterinary Medicine. 11th ed. Elsevier, London.
Kamal, M.A., Rashad, A.M., and El-Sayed, A. 2024. Effect of drinking water quality on immunity and mortality in dairy calves. Archives of Animal Breeding 67:25–38.
Klein-Jöbstl, D., Iwersen, M., and Drillich, M. 2014. Farm characteristics and calf management practices associated with diarrhea. Journal of Dairy Science 97(8):5110–5119.
Le, O.T., Dart, P.J., Harper, K., et al. 2016. Effect of probiotic Bacillus amyloliquefaciens H57 on diarrhoea in dairy calves. Animal Production Science 56:1990–1998.
Münster, P., Heitmann, S., and Truyen, U. 2024. Drinking-water biofilm development in livestock systems. Frontiers in Animal Science 5:1467287.
NADIS. 2023. Calf Scour in Beef and Dairy Rearing Units. NADIS, UK.
Robertson, L.J., Björkman, C., Axén, C., and Fayer, R. 2014. Cryptosporidiosis in farmed animals. Parasitology 141:1455–1475.
Ryan, U., Fayer, R., and Xiao, L. 2021. Cryptosporidium in humans and animals. Clinical Microbiology Reviews 34:e00062-19.
Thomson, S., Hamilton, C.A., Hope, J.C., et al. 2017. Bovine cryptosporidiosis and control strategies. Veterinary Research 48:42.
Trotz-Williams, L.A., Jarvie, B.D., Martin, S.W., et al. 2007. Calf-level risk factors for neonatal diarrhoea. Preventive Veterinary Medicine 82:12–28.
World Health Organization. 2020. Antimicrobial Resistance. WHO,