Summer Scour in calves

Summer Scour Syndrome is characterised by signs of scour and rapid weight loss of calves at grass not associated with common infections or worm burdens

Affected calves can also show lethargy, weakness and lack of rumination, which can progress to profound weakness and death. Some calves may develop ulcers on the muzzle, mouth or oesophagus. Not all calves in the group are affected and severity can vary from year to year and farm to farm. It typically occurs in dairy calves up to 12 months of age within a month of turnout. Conventional scour treatments seem ineffective and calves only improve once removed from grass.

The cause of Summer Scour Syndrome is still being explored. As a relatively new condition, summer scour hasn’t been widely researched yet and current advice is reliant on practical experience. Multiple theories exist as to what the most likely risk factors are, but the one common factor to all cases is a grazing diet (exclusively or partially) in first grazing season calves. An infectious cause has not yet been identified and the disease is thought to relate to nutritional issues, such as when the rumen is insufficiently developed to digest forage. Only when the common causes of diarrhoea and weight loss in grazing calves are ruled out (using faecal samples, grass trace element analysis, trace element blood testing and response to treatment/supplementation), can a diagnosis of summer scour be made with more confidence. Summer Scour Syndrome is more common in calves grazing 'rich' or 'lush' pastures, typically with a high crude protein (greater than 20%) and low fibre (less than 40%) content per kg of dry matter ingested. Calves are selective grazers and preferentially consume the top, leafier parts of the grass, which contain more nitrates and non-protein nitrogen (NPN). It is suspected that consumption of large quantities of nitrates and NPN by young calves, with immature rumen development might lead to an excessive build-up of ammonia in the rumen. Inadequate rumen development may also lead to an unstable pH for rumen microbes to function appropriately which may also potentially contribute to the syndrome.

Other conditions which may resemble summer scour are: Coccidiosis, high gut worm burden, mineral issues such as molybdenum toxicity and copper toxicity, rumen acidosis, Salmonellosis, BVD, Corona virus

Treatment options for summer scour need to be discussed with your veterinary practitioner, as there is no single cure that works in all cases. Symptomatic and supportive treatment for scour should be used as quickly as possible. Keep in mind that affected calves can be immunosuppressed and more prone to other diseases that require separate treatment.

It is important to monitor dairy calves closely for evidence of diarrhoea and weight loss during their first 4 to 6 weeks post turnout to grass. If summer scour is suspected, then affected calves should be removed from grass immediately. The earlier that calves are removed from grass the greater the chance of recovery for the calves involved. This may only involve housing 10-20% of the calf group, as usually only a small proportion of calves are affected. Housed calves should be fed good quality forage such as hay, silage or straw along with a good quality calf concentrate and have ad-lib access to water. Following a period of 4-6 weeks, if calves are recovered sufficiently, they can be returned to a pasture that is not lush and provided with access to extra fibre and good quality concentrates

STEPS TO PREVENTION:

Review calf rearing process - Discuss with your veterinary practitioner and farm advisors if your calf rearing strategy is optimal. It may be appropriate to delay weaning to at least 10 weeks of age.

Wean calves gradually - Gradual weaning ensures a smooth transition from a milk diet to a forage diet, concentrates should be introduced to calves from the first week in life. Begin weaning up to 4 weeks before removing milk completely and calves should be eating at least 1kg of concentrate daily consistently before weaning. See GAIN Heifer Rearing Programme for weaning guidelines.

When weaning, make no other dietary changes - Other dietary changes will increase stress and take longer for the calf to adjust. For farms with Summer Scour Syndrome issues and depending on the farm facilities and the type of grazing available, it might be worthwhile to consider retaining calves indoors on a concentrate and high fibre diet for at least 1 week after weaning before turnout to pasture.

Ensure calves have high levels of fibre in the diet from stemmy grass or older swards, when first turned out to pasture - Calves need adequate levels of fibre and on farms with Summer Scour Syndrome issues, this may include grazing more stemmy grass covers or providing an additional fibre source (straw or hay). For farms with these issues, calves should avoid grazing reseeded pastures, or paddocks with very leafy (lush) grass for at least 2 months after turnout.

Strip graze calves to encourage consumption of both the leaf and stem of the grass - Calves may prefer more lush grass but may not be able to digest large amounts of it.

Avoid pastures that have had slurry or nitrogen applied recently - Slower growing pastures have less nitrogen and more fibre.

First Published 10 June 2022