Tackling Summer Scour Syndrome in Weaned Calves: Insights and Strategies

Summer Scour Syndrome (SSS) is an issue which appears to be reported upon more frequently with every passing year and consequentially it is a major topic of conversation when calves are at grass. It primarily affects groups of young, recently weaned dairy calves during their first grazing season in late spring and early summer, with recurrent issues occurring on many farms. The condition is characterised by an acute onset profuse and watery diarrhoea, alarming body condition wastage, coat discolouration, lethargy, lack of rumination, dehydration, and in some instances, ulceration along the gastrointestinal tract and death. SSS poses significant challenges to calf health and farm productivity. In the sixth episode of Precision Microbes’ ‘Tech in 10’ series, veterinary consultant Tommy Heffernan MVB CertDHH and veterinary ruminant specialist Ryan Duffy MVB CertDHH MSc delve into the complexities of SSS, exploring some of its potential causes, impacts, and effective management strategies.

Understanding Summer Scour Syndrome

SSS typically emerges in calves aged 8-12 weeks of age, often shortly after weaning from milk and turn-out during periods of peak grass growth. Unlike neonatal calf diarrhoea which can be caused by a range of recognised pathogens (see Table 1), to date no infectious agent has been definitively diagnosed as the primary cause of SSS. Therefore, it is suspected that SSS may be more closely linked to nutritional and management stressors.

Suspected key contributing factors include:

• Abrupt Weaning Practices: It is highly recommended that calves experience a slow and steady weaning policy as they transition from a milk-based diet to the forage-based diet expected of a mature ruminant. This can induce unnecessary stress on the animal, predisposing to a plethora of infectious disease processes, while also disrupting the gut microflora and digestive processes. After all, it is widely accepted that it takes 4-6 weeks for the rumen to fully adapt to a new diet.

• Rumen Underdevelopment: Calves may not have a fully developed rumen at the time of weaning, impairing their ability to digest the new complex, forage-based diet expected of a mature ruminant. We must all appreciate that these 8-12 week old calves must undergo significant anatomical, physiological, and microbiological transformations to facilitate the utilisation of this complex diet.

• Grassland Management: The predominance of rapidly growing, lush perennial ryegrass swards during late spring and early summer poses a unique risk to an immature ruminant. There are suspicions that a high water-soluble carbohydrate level (i.e., high sugars), low complex carbohydrate level (i.e., low fibre), high crude protein levels (especially if recent fertiliser applications), high unsaturated fatty acid levels (i.e., high oils/fats), or various combinations of these, may have negative associative effects in the immature reticulorumen, with a resultant gastrointestinal dysbiosis.

Clinical Signs and Diagnosis

Suspected cases of SSS are often diagnosed by a process of excluded common gastrointestinal ailments which would affect recently turned-out calves such as coccidiosis (caused by Eimeria species) and parasitic gastroenteritis (caused by a variety of worms such as Ostertagia Ostertagi, Haemonchus Placei, Trichostrongylus Axei, Cooperia species, and Nematodirus species).

Following the exclusion of common ailments through laboratory testing, identifying SSS involves observing a combination of the described clinical signs and understanding the recent farm history (in respect to weaning policy and pasture management).

Precision Microbes offers a unique liquid probiotic and postbiotic solution specifically designed to stabilise gut flora and enhance digestive health in calves. The product acts rapidly, with postbiotic components working quickly to restore normal gut function. Its liquid formulation allows for easy administration, whether given orally or mixed with milk. It is also compatible with other treatments, making it safe to use alongside antibiotics and rehydration therapies. The dosing is flexible and can be tailored depending on the calf’s age and the severity of symptoms, making it a practical and effective tool for managing gut health during critical periods like weaning.

Management and Prevention Strategies

Effective management of Summer Scour Syndrome requires a multifaceted approach focusing on nutrition, environment, and gut health support.

1. Nutritional Management

• Gradual Weaning Policy: Implementing a step-down approach to milk feeding pre-weaning promotes the voluntary intakes of solid feeds and therefore assists the adaptation of the reticulorumen to a mature ruminant diet, reducing potential digestive disturbances. It is recommended to carry this out over 2-4 weeks to minimise weaning stress.

• Ensure Adequate Intake Of Calf Starter Ration: Pre-weaned calves should be consuming between 1.5-2.0Kg of a high quality, palatable starter ration per calf per day for at least 3-5 days before the withdrawal of milk/milk replacer supply. This yields the energy dense volatile fatty acids, Butyrate and Propionate, which are required for rumen papillae and microvasculature development and metabolisable energy for maintenance and growth, respectively. This also allows for the expansion of amylolytic microbial agents in the rumen fluid.

• Provide High Quality Young Forages: Young and digestible straws and hays, chopped to 3-4cm in length, are preferred in pre-weaned calves, whilst longer strands can be provided to those post-weaned calves at grass in a round feeder. Providing physically effective fibre stimulates the development of the two muscular layers of the rumen – the scratch factor – while also promoting an expansion in rumen volume. This yields another energy source, Acetate, and facilitates the expansion of cellulolytic microbial populations which are needed for processing a complex forage-based diet.

• Ensure Access To Clean Water At All Times: This is often the ‘forgotten nutrient’ but should not be overlooked in any calf management system. This is because water is absolutely essential for rumen microbial growth, overall health, and the desired chemical fermentation process which occurs in the rumen.

2. Grassland Management

As these calves are expected to graze the available swards following weaning, and that SSS appears to be an issue at grass, grassland management has received some scrutiny when this topic is being discussed. The grasses in late spring and early summer are rapidly growing and therefore exhibit a high leaf:stem ratio. Calves are renowned for selectively grazing the highly nutritious leaf and leaving stem behind them if given the opportunity. Consuming only the lush components of the plant raises concerns as this promotes rapid gut transit, a lack of consumption of fibre and therefore rumen buffering, and a high consumption of crude protein, oils, and simple sugars. Plus, there are concerns around non-protein nitrogen, nitrates, and mineral deficiencies (such as those seen with copper and molybdenum issues). Timing and level of inorganic nitrogen fertiliser application pre-grazing is also being investigated.

This is why it is frequently recommended to turn at-risk calves out to rougher pastures, which had less inorganic nitrogen fertiliser applied. If this is not possible then strip grazing is suggested to promote the intake of the leaf and stem of the young plant. This can be supported by continued concentrate feeding and providing physically effective fibre, in the form of straw or young hay, in a round feeder. Severe cases may need to be re-housed to remove any potential disease exacerbation if maintained at grass.

3. Gut Health Support with Precision Microbes

Precision Microbes offers a unique probiotic and postbiotic liquid formulation specifically designed to stabilise gut flora and enhance calf digestive health. This complimentary dietetic feed contains live bacteria and therefore acts rapidly, while also being palatable and easy to administer – it can be given orally, mixed with milk, or top dressed on concentrates. This supportive therapy can complement antibiotic and oral rehydration treatments in addressing digestive upsets.

Precision Microbes offers a unique liquid probiotic and postbiotic solution designed to stabilise the gut flora and enhance digestive health in calves. Dosage of this zootechnical additive can be adjusted based on the severity of clinical signs and calf age, under veterinary guidance.

In the case of risk of, during periods of, or recovery from digestive disturbance, the product can be used as part of supportive care. Where loose faeces or diarrhoea is observed administer 60ml orally (veterinary administration or supervision), twice daily, as a physiological digestive stabiliser for up to 3 days.

Conclusion

SSS presents a significant challenge in calf rearing, particularly during the weaning transition from pre-ruminant to pseudo-ruminant, to functional ruminant. By understanding the potential underlying causes and implementing comprehensive management strategies – including nutritional adjustments, and gut health support with Precision Microbes – farmers and veterinarians can effectively mitigate the negative impacts of SSS. Proactive measures and vigilant monitoring are key to ensuring optimal calf health and farm productivity during the summer months.