Technical Tip - Calf Scour

UMMARY Calf scour is a prevalent condition in young calves, caused by various factors including bacterial, viral, and parasitic infections, dietary changes, stress, and environmental conditions. Treatment options for calf scour include supportive care with oral rehydration solutions, targeted antimicrobial therapy or IV fluids when necessary, and probiotics or nutritional supplements to support gut health and aid in recovery. Prevention of calf scour involves health management through vaccination, regular monitoring for signs of illness, strict biosecurity protocols, maintaining clean housing environments, and ensuring proper nutrition. Natural alternatives such as Orego-Stim, have shown numerous benefits in calves including managing calf scour, and can reduce reliance on antibiotics. BACKGROUND Calf scour, also known as diarrhoea, is a condition characterised by frequent and watery bowel movements in calves. It is the largest health issue affecting young calves, especially within the first few weeks of life. Calf scour can be caused by various factors including infectious agents such as bacteria, viruses, and protozoa, as well as non-infectious factors like dietary changes, stress, and environmental conditions. The monetary cost of calf scour to farmers can vary depending on various factors such as the severity of the outbreak, the number of affected calves, the cost of treatment, and any associated losses such as reduced growth rates, increased mortality, and veterinary expenses. A lower weight at weaning has a significant impact on first lactation milk yield performance (Chester-Jones, et al., 2017). Additionally, indirect costs such as labour and management time spent on dealing with the outbreak can also contribute to the overall financial impact.  Specific figures may vary, but a widely referenced report from 2013 (Vickers & Wright) estimated that the economic cost of calf scour to UK farmers was approximately £58 per calf affected. This cost includes both direct expenses such as treatment costs, as well as indirect costs related to reduced growth rates and increased mortality. CAUSES AND SIGNS OF SCOUR Bacterial Several bacteria can cause calf scour, including Escherichia coli (E. coli), Salmonella spp., Clostridium spp., and others.  E. coli is a gram-negative bacterium commonly found in the intestines of healthy animals, including calves. However, certain strains of E. coli can cause diarrheal illness. In calves, enterotoxigenic strains (containing the K99 antigen) of E. coli are often responsible for yellow-white calf scour, especially in days 1-3. These strains produce toxins that lead to fluid secretion and inflammation in the intestines. Salmonella is a genus of gram-negative bacteria. Once ingested, Salmonella bacteria invade the intestinal lining, where they multiply and produce toxins that damage the intestinal epithelial cells. This damage disrupts the normal absorption and secretion processes in the intestines, leading to diarrhoea. The diarrhoea associated with Salmonella infection is often watery, foul-smelling, and may contain blood or mucus. Calves tend to be affected between weeks 2-6.  Clostridium is a genus of gram-positive, spore-forming bacteria, often occurring due to overeating, poor weather, or poor digestibility and mixing of milk replacer. Clostridium infections tend to be around 2 weeks of age. Clostridium perfringens (types A, B, and C) and Clostridium difficile are two species within this genus that can cause calf scour. Clostridium perfringens produces toxins that damage the intestinal lining, leading to diarrhoea and abdominal pain. Clostridium difficile infection can occur secondary to antibiotic use, leading to an overgrowth of this bacterium in the intestines and causing diarrhoea and colitis. Viral Viruses such as rotavirus, coronavirus, and bovine viral diarrhoea virus (BVDV) can also cause calf scour.  Rotavirus is one of the most common causes of calf scour. The infection typically occurs through the ingestion of contaminated faecal material or through contact with infected animals or their environment. Once ingested, rotavirus infects the cells lining the small intestine, leading to damage and disruption of normal intestinal function. The resultant diarrhoea is often yellowish or green, with a characteristic foul odour. Calves tend to be affected between 1-2 weeks.  Coronavirus causes diarrhoea which is similar to, or more severe than, those observed for rotavirus infection. Fortunately, coronavirus infection is much less common than rotavirus. Infection tends to be seen in weeks 13.  Bovine Viral Diarrhoea Virus (BVDV) belongs to the Pestivirus genus within the Flaviviridae family. BVDV exists in two biotypes: cytopathic (CP) and non-cytopathic (NCP), with the latter being more common and causing persistent infections. Persistently Infected (PI) Calves are born following infection of the dam during pregnancy with NCP BVDV. These calves carry the virus for life and shed it continuously, serving as a source of infection to other cattle. They may appear healthy or show signs of ill-thrift, but they remain highly susceptible to other infections and often have stunted growth. PI animals that become superinfected with a CP strain of BVDV can develop mucosal disease, a severe and often fatal form of the disease characterised by erosions and ulcerations in the gastrointestinal tract, diarrhoea, oral lesions, and weight loss. BVDV is primarily transmitted through direct contact between cattle, such as nose-to-nose contact, aerosols, and through the ingestion of contaminated materials such as feed, water, or milk. Additionally, transmission can occur through PI animals shedding the virus into the environment. Parasitic Parasites like Cryptosporidium parvum (cryptosporidiosis) and Eimeria (coccidiosis) are common causes of calf scour.  Cryptosporidiosis is a parasitic disease, caused by the protozoan parasite Cryptosporidium, with Cryptosporidium parvum being the most common species affecting calves, usually in the first 1-3 weeks. Cryptosporidiosis scour can range from mild to severe and can lead to dehydration, weight loss, and even death, especially in young calves. Transmission of Cryptosporidium occurs through the ingestion of oocysts (eggs), the environmentally resistant stage of the parasite, which are shed in the faeces of infected animals. Calves can become infected through direct contact with contaminated faeces, ingestion of contaminated milk or feed, or exposure to contaminated environments such as calf pens. Once ingested, Cryptosporidium oocysts release sporozoites that invade the lining of the small intestine, where they replicate and cause damage to the intestinal epithelium. This damage disrupts normal intestinal function, leading to malabsorption of nutrients and electrolytes and resulting in diarrhoea. Clinical signs of cryptosporidiosis in calves typically include profuse, watery diarrhoea that may contain mucus and sometimes blood.  Coccidiosis is a parasitic disease caused by various species of protozoa belonging to the genus Eimeria, usually E. bovis or E. zuernii. Coccidiosis is typically transmitted through the ingestion of oocysts, the environmentally resistant stage of the parasite, which are shed in the faeces of infected animals. Calves become infected by ingesting oocysts from contaminated feed, water, or the environment. Coccidiosis is more prevalent in crowded or unsanitary conditions where the concentration of oocysts is higher. Once ingested, the oocysts release sporozoites that invade the intestinal lining, where they reproduce and cause damage to the intestinal epithelium. This damage disrupts normal intestinal function, leading to malabsorption of nutrients and electrolytes, as well as inflammation and damage to the intestinal mucosa. The severity of coccidiosis in calves can vary depending on factors such as the species of Eimeria involved, the calf's age, immune status, and environmental conditions. Clinical signs of coccidiosis in calves may include diarrhoea (which can be bloody or watery), dehydration, weight loss, decreased appetite, weakness, and in severe cases, death. Calves tend to be infected with coccidiosis between three weeks and six months.

Other There are many other, often indirect, causes of calf scour. Failure to receive an adequate amount of colostrum shortly after birth can weaken a calf's immune system, making them more susceptible to infections that cause diarrhoea. Factors such as cold weather, wet bedding, overcrowding, and poor sanitation can stress calves. Consumption of contaminated colostrum, milk, or feed can introduce pathogens into a calf's digestive system. Weaning is a stressful period for calves, and stress can predispose them to gastrointestinal infections and diarrhoea. Sudden changes in diet or feeding practices can upset the balance of microbes in the calf's gut. Poor hygiene, inadequate ventilation in calf housing, and improper manure management can contribute to the spread of pathogens that cause calf scour.  

TREATMENT OPTIONS Treatment options for calf scour typically involve a combination of supportive care, oral rehydration therapy, and targeted antimicrobial therapy when indicated. Oral rehydration solutions (ORS) are commonly used to replace fluids and electrolytes lost due to diarrhoea in calves. These solutions contain a balanced mixture of electrolytes, glucose, and water to help restore hydration and electrolyte balance. ORS products specifically formulated for calves are available and can be administered orally using a bottle, tube feeder, or oral electrolyte drench. In severe cases of dehydration, intravenous fluid therapy may be necessary to rapidly restore fluid and electrolyte balance. This typically requires veterinary intervention. Any electrolytes fed to calves must meet EU regulation No. 1123/2014, which requires that all scour treatments must have an SID of at least 60mmol/litre which will assist in correcting acidosis. Antimicrobial therapy may be prescribed by a vet in cases of bacterial calf scour where systemic signs of illness are present or when there is a high risk of bacterial involvement (e.g., in cases of calf pneumonia or septicaemia). Commonly used antibiotics for treating bacterial calf scour in calves include sulphonamides, fluoroquinolones, and tetracyclines. It's important to note that the use of antibiotics should be based on veterinary diagnosis and guidance to minimise the development of antimicrobial resistance. 

Probiotics or nutritional supplements can also be used to support gut health and aid in recovery from calf scour. These products are typically administered orally and may contain beneficial bacteria or prebiotics to help restore the balance of gut microbiota. TREATMENT ISSUES While treatments for calf scour can be effective in many cases, there are several issues and challenges associated with their use. Some of these issues include: Antimicrobial Resistance. The indiscriminate use of antimicrobial drugs to treat bacterial calf scour can contribute to the development of antimicrobial resistance (AMR) in bacterial pathogens. Overuse or misuse of antibiotics can lead to the selection of resistant bacteria, reducing the effectiveness of antimicrobial treatments and posing a threat to both animal and human health. AMR can also develop through misdiagnosis. Calf scour can have various underlying causes, including viral, bacterial, and parasitic infections. The failure to identify the specific cause of calf scour can result in inappropriate treatment with antimicrobials or other medications that may be ineffective or unnecessary, leading to treatment failure and prolonged illness in affected calves. Antimicrobials may also have an environmental implication due to their potential contamination of water sources with drug residues. Sustainable and responsible use of antimicrobial treatments is necessary to minimise their impact on the environment. Lack of specificity and efficacy. Some treatments for calf scour, such as electrolytes, provide supportive care by addressing dehydration and electrolyte imbalances, but do not directly target the underlying cause of the scour. While supportive care is essential for managing calf scour, it may not be sufficient to resolve the underlying infection or condition responsible for the diarrhoea. Certain pathogens causing calf scour, such as some strains of E. coli or Cryptosporidium parvum, may be less responsive to treatment, making it challenging to achieve successful outcomes with standard treatment regimens. Parasitic infections are particularly stubborn to treat, due to the tough outer casing of the oocysts. Cost and Availability. Some treatment options for calf scour, particularly antimicrobial drugs, may be costly or not readily available in certain regions or countries. This can limit access to effective treatments for farmers and vets, particularly in resource-limited settings.  Timing. By the time calf managers have identified calves are needing spot treatment with electrolytes or IV fluids, the effect of scour and dehydration has already had some negative effect on growth performance and milk or feed intake. There is also a secondary effect to calf scour, enabling other conditions such as pneumonia to take advantage of the weakened calf. PREVENTION Preventing calf scour requires a comprehensive approach that addresses three main areas contributing to disease.  Health • Follow a targeted vaccination program to protect calves against common pathogens that cause calf scour, such as rotavirus, coronavirus, Escherichia coli (E. coli), and Cryptosporidium parvum.  • Consult with a vet to develop a vaccination strategy tailored to the specific disease risks in your herd.  • Regularly monitor calves for signs of illness, including diarrhoea, dehydration, lethargy, and poor appetite.  

Implement a surveillance program to detect and monitor calf scour outbreaks early, allowing for timely intervention and control measures. Environment • Implement strict biosecurity protocols to prevent the introduction and spread of infectious agents that can cause scour. This includes quarantining new animals, limiting contact with other herds, and practicing good hygiene to minimise the risk of disease transmission. • Maintain clean and dry housing environments for calves, including calf pens, barns, and other facilities.  • Regularly clean and disinfect calf housing areas to reduce the buildup of pathogens and minimise the risk of disease transmission. • Manage calf housing environments to minimise stressors and promote optimal health. Provide adequate ventilation, temperature control, and bedding to create a comfortable and hygienic environment for calves.  • Implement proper manure management practices to reduce the risk of pathogen contamination in the environment. Nutrition • Ensure calves receive an adequate intake of high-quality colostrum shortly after birth to provide passive immunity against common pathogens that cause calf scour.  • Proper colostrum management includes timely colostrum feeding, testing colostrum quality, and ensuring calves consume an adequate volume of colostrum. • Provide calves with nutritionally balanced diets that meet their specific nutritional needs.  • Avoid abrupt changes in diet and feeding practices that can disrupt gut health and increase the risk of calf scour.  • Make sure either whole milk or milk replacer is fed at the appropriate volume by age of calf, to avoid under- or overfeeding.  OREGANO ESSENTIAL OIL Natural oregano essential oil (OEO) has many properties, including antimicrobial, antioxidant, and immunomodulatory functions. OEO contains over 100 compounds, such as carvacrol and thymol, which have been shown to have these functions in many species, including calves. Some components of OEO also possess anti-inflammatory properties, which could help in reducing inflammation in the gut associated with scour. By decreasing inflammation, OEO may contribute to alleviating discomfort and promoting healing of the intestinal lining. With increasing concerns about antibiotic resistance and the desire for natural alternatives, OEO presents itself as a potential candidate for managing scour without relying solely on antibiotics. OREGO-STIM Developed to manage intestinal health and support an optimum gut microbiome, integrity, and performance, Orego-Stim is a consistently high quality, 100% natural OEO based feed additive. It has been formulated to be low inclusion and free flowing for inclusion in milk and calf starter rations, providing an effective, homogenous mix. The recommended inclusion of Orego-Stim Liquid for calves is 10ml per head per day for the first 10 days, followed by 2-5ml per head per day until weaning.  Producers can then follow this on with Orego-Stim Powder, formulated in calf starter at an inclusion of 1kg/tonne, to help smooth the transition from milk to feed.  

REFERENCES Chester-Jones, H., Heins, B.J., Ziegler, D., Schimek, D., Schuling, S., Ziegler, B., De Ondarza, M.B., Sniffen, C.J. and Broadwater, N., 2017. Relationships between early-life growth, intake, and birth season with firstlactation performance of Holstein dairy cows. Journal of Dairy Science, 100(5), pp.3697-3704. Vickers, M. & Wright, N. 2013. Economic Impact of Health and Welfare Issues in Beef Cattle and Sheep in England.