Summer scour is a relatively new phenomenon that is being seen in dairy calves at grass on Irish farms.

Grazing management on dairy farms has improved greatly over the last number of years, and there is some indication that this may be linked to summer scour.

A calf’s rumen is not fully developed so they are unable to handle the high-quality leafy grass they are being offered.

It is also believed that an excessive intake of nitrogen leads to ammonia toxicity and the resulting scouring and wasting in the calves.

Although it goes against what many would think, it may be better to offer calves grass with more fibre. Calves fed on coarser, more fibrous grass rarely suffer from the condition.


Usually, the affected calves don’t respond to conventional treatment.

Summer scour causes calves to scour profusely, become dehydrated and lose weight rapidly a few weeks after turnout to grass.

It often results in a calf falling behind its targets, which it may struggle to regain.


There is currently no vaccination or treatment for summer scour, so the best way to deal with it is to try and prevent it.

A practical way of preventing summer scour is by offering calves fibre while at grass in the form of hay or straw.

Keep the hay or straw fresh and continue to offer it to calves for the first number of months they are at grass.