23 October 2024

Search continues for cause of summer scour syndrome

Theories aplenty, but as of yet there has been no clear confirmation of the cause of summer scour syndrome – an ailment of dairy and dairy-beef calves resulting in diarrhoea, ill-thrift and weight loss.

That was one of the key messages delivered by John Donlon, Beef Herd Health Research Officer at Teagasc Grange, who addressed delegates at the International Dairy Calf to Beef Conference, organised by Teagasc in partnership with ABP and BSAS, in Co. Wexford recently.

With cases witnessed in Ireland, Australia, New Zealand and the UK, Donlon explained that the syndrome primarily occurs in calves in their first grazing season; reports on the prevalence of its occurrence can vary from year to year.

Diagnosis

Making diagnosis of summer scour syndrome difficult at farm level, he explained, is the wide array of clinical signs – ranging from diarrhoea, ill-thrift, weight loss, ulceration of the mouth and oesophagus in some cases, browning of the coat, and death in severe cases. These symptoms are often associated a number of other diseases, such as parasite burdens, coccidiosis and even chronic pneumonia, to name just a few.

“The clinical signs are quite vague. You are not going to be able to make a diagnosis of summer scour syndrome by just looking at calves. When advising vets and farms on how to tackle this problem, the first thing to do is actually rule out all of the other much more common causes such as parasites and respiratory disease,” Donlon added.

Along with this, completing a forage analysis was recommended to rule out molybdenosis – a scour and ill-thrift causing disease occurring where excess molybdenum is present within the pasture.

John Donlon, Beef Herd Health Research Officer at Teagasc Grange, pictured at the International Dairy Calf to Beef Conference, organised by Teagasc in partnership with ABP and BSAS, in Co. Wexford recently

Vet survey and research at Teagasc Grange

Reporting on a survey of practicing vets whose theories were gathered on the potential causes of summer scour syndrome, Donlon explained that the finger was pointed toward:

1. Insufficient weanling protocols with inadequate quantities of concentrate offered to ensure rumen development;
2. The grazing of very lush grass by recently weaned calves, thus potentially causing sub-acute ruminal acidosis due to its high carbohydrate content;
3. And, nitrogen rich grass exerting pressure on the microbes in the rumen and resulting in higher rumen and blood ammonia levels.

As opposed to ruling any of these out as the possible cause, Donlon instead told those in attendance: “It is very possible that on a lot of these farms with summer scour syndrome, calves maybe weaned too quickly and are then put out to highly palatable grass that they are not really set up to metabolise. These are all theories currently, one of them maybe true but it is also possible that a couple of them are true.”

To examine these theories further, a team from Teagasc and UCD School of Veterinary Medicine visited five farms in June 2023 with suspected cases of summer scour syndrome and completed a clinical investigation. Two farms were designated as non-summer scour syndrome case farms after confirmation of coccidiosis or chronic pneumonia. Three farms were classified as having summer scour syndrome.

Citing this study undertaken by Rischi Robinson, a Walsh Scholar in the Teagasc Animal and Bioscience Programme, Donlon said: “Probably the most interesting finding of this work was that the blood ammonia was a lot higher in the case farms than the non-case farms and similarly the blood urea nitrogen was higher as well.

“That would lend some credence to excess non-protein nitrogen, but it is putting the cart before the horse to say that is definitely the case because you will get cases where animals that are scouring will have increased ammonia; it may be the case that the ammonia is causing the scour or it may be the case that this is simply a symptom of the animals already scouring. We need to do more work to actually definitively say that is the case.”

This work includes an investigation of nitrogen fertilisation application rates, currently ongoing in Teagasc Grange, which hopes to shed light on if there is a link between artificial nitrogen application strategies and the potential occurrence of summer scour syndrome.

In the meantime and until a definite cause of summer scour syndrome has been found, Donlon advised farmers to focus on a number of on-farm strategies that may aid in its prevention. These include:

• Wean calves gradually, making sure that are consuming sufficient concentrate and forage before moving to grass.
• Consider strip grazing calves instead of offering them generous allocations of grass. This will enable calves to consume more fibre as they graze lower into the sward profile, as opposed to being selective and only consuming the leafiest grass.

For more insights on summer scour syndrome, John Donlon’s paper as delivered to the International Dairy Calf to Beef Conference is available to read here.

Diary date – Teagasc National Beef Conference

The Teagasc National Beef Conference 2024 takes place on Tuesday, 19 November at 5pm in the Landmark Hotel, Carrick-on-Shannon, Co. Leitrim, N41 N9W4.

The theme of the conference is ‘Sustainable Beef Farming: Pathways to a greener future’.