Many calves are out grazing at the moment, and they can all seem fit and healthy before suddenly taking a turn to summer scour syndrome.
Summer scour is a terribly frustrating disease that primarily affects young calves grazing lush, protein-rich pastures with little fibre in the diet.
The annoyance with the disease is that, at this point, many feel all the hard work has been done – after getting calves their colostrum and onto milk to successfully weaning them off milk – only for them to get a setback and life-threatening disease such as summer scour.
The true cause of the disease is still unknown but it is thought to be related to nutritional issues, such as the quality of grass being offered to calves and an excessive intake of nitrogen (N), which leads to ammonia toxicity.
The rumen may be insufficiently developed to digest grass, as a calf’s grazing diet in the first year is a common denominator in all cases of summer scour.
Summer scour
The condition sees calves experiencing dehydration, rapid weight loss, scour, lethargy, lack of rumination, and weakness, which can ultimately lead to death.
This can happen only a few weeks after turnout to grass, resulting in calves falling behind targets, which can be difficult to regain.
Sick calves should be separated and fed extra meal with a bit of milk to get them back up to speed, ensuring they have access to hay or straw and water.
The disease often occurs when calves are grazing lush pastures with a high crude protein (CP) content (>20%) and a low fibre content (<40%).
If their rumen is not properly developed and they continue grazing the leafier parts of the grass which contain more nitrates and non-protein nitrogen (NPN), a large quantity of ammonia may build up in the rumen.
Unstable pH is another knock-on effect of inadequate rumen development, which may lead to the calf getting summer scour.
Calves should be let out to paddocks of covers less than 1,000kg of dry matter (DM)/ha as these covers will encourage intakes and they should ideally be offered fresh grass every three to four days.
How to prevent it?
By now, most calves will be weaned off milk, but this is a critical point as there needs to be a gradual weaning for calves, with an appropriate transition from milk to grass.
In order to allow for rapid rumen development, concentrates should be added to the diet within the first week of life.
At four-weeks-of-age, the gradual weaning should begin and, prior to milk being stripped from the diet completely, calves should be eating 1kg of concentrates/day.
Making any dietary changes should be avoided as it will only cause stress on the calf and take the animal longer to adjust.
As calves are unable to handle high-quality grass, it may be better for them to have access to more fibre – calves that are grazing on more fibrous grass rarely suffer from the disease.
A practical way of correcting the fibre deficit for calves is to introduce hay or straw into their diet while they are out at grass.
When calves are first turned out to grass, they should continue to receive about 1.5-2kg of meal for about five to six weeks after tun-out to transition them fully to grass.
If the weather is good and calves are in good form, they can be taken off meal from around mid-June before being re-introduced in September. Any weak or late-born calves should be kept on meal for the summer months.
Strip grazing calves is another possible method to prevent the onset of summer scour as it will encourage them to graze both the leaf and the stem of the grass.
It is crucial in the first four to six weeks after turnout to grass to closely monitor your calves for any evidence of scour and weight loss so you can detect the condition early and treat accordingly.
Another thing to consider during this mild and damp weather is lungworm issues. Farmers need to be wary about getting calves out to the same paddock year after year, as altering the paddock will help avoid the build-up of pathogens and diseases.
