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Top tips for preventing summer scour syndrome in calves
Early life nutrition is a key player in protecting the health status of young calves. Although turnout is largely dictated by weather and ground conditions, for calves it mostly happens in late spring. While grass is a cheap source of feed, it must be managed well if calves are to reap the benefits from it and avoid issues such as summer scour syndrome.
As the name might suggest, the syndrome results in calves scouring when they are at grass and they also get oral ulcerations, rumination is reduced and thrive is lost over a period of time. These symptoms can be similar to other conditions so it is always best to undertake faecal egg counting to diagnose or rule out other likely suspects such as coccidiosis, worms and mineral deficiencies.
So what are the causes of summer scour syndrome and how can calves be managed better at turnout?

Dr Amanda Dunn, of Bonanza Calf Nutrition, says consideration must be given to how calves transition from a dry and cosy indoor bedded situation to a diet of grass in an environment where they are dealing with different weather conditions, often without much shelter. Weather and sudden changes in diet tend to increase stress levels which can predispose calves to disease, she says.
To help ease the transition, shelter and feed supplementation should therefore be available, especially for younger spring born-calves. It is important to be mindful of the type of pasture young calves are offered, says Dr Dunn. “Is it lush grass high in sugars, oils and maybe nitrogen? Unlike fibre, these components are not favourable to a young, undeveloped rumen.’’
Calves rely on the microbes in their rumen to degrade and ferment food into short chain fatty acids and microbial proteins that they can utilise. When calves were housed, these microbes would have been used to break down concentrates and forage such as straw, hay and silage, all of which are high in fibre.
Each time the diet changes, the rumen microbes also change. “It takes about a fortnight for the rumen to adjust and be able to utilise the new feed source such as grass,’’ Dr Dunn explains.
The first grazing season is the calf’s introduction to grass so it will take time for them to explore and learn how to graze.

Having access to both housing and pasture prior to turnout is advantageous as this will get calves accustomed to grass. Calves often prefer the top of the grass plant which contains the most nitrogen and don’t eat the full stem, the component which provides the necessary fibre element.
High concentrations of nitrogen can sometimes lead to acidosis-type symptoms, Dr Dunn warns. Calves born later in the spring won’t have weaned for long before they are turned out to grass, a process that can sometimes be rushed. “These calves may have been weaned too early, before their rumen has fully developed and is incapable of digesting solid feed successfully,’’ says Dr Dunn.
“These are likely victims of summer scour syndrome as their rumen isn’t fully developed and cannot cope with the consumption of grass as they are unable to break it down and utilise it.’’
A gradual step-down weaning protocol is important in the transition from milk to solid feed as this allows the rumen microbiome to adapt and develop.
Summer scour syndrome can greatly impair the rumen function of calves and this results in the rumen being unable to generate B vitamins. Severe B vitamin deficiency can result in blindness, says Dr Dunn. “Before a deficiency gets the chance to develop it may be the case that calves should be taken off grass and reintroduced to milk as a source of B vitamins,’’ she suggests.
Overall, rumen health and weaning management have major roles to play in preventing the onset of summer scour syndrome. Promoting rumen development in the early days by providing calves with access to fresh concentrates, clean water and roughage is therefore essential. Secondly, a gradual step-down weaning approach is best as this allows a smooth transition and successful rumen function.
Also, provide calves with familiar feeds alongside their new grass option to prevent gorging on lush grass and supply necessary fibre in the diet, Dr Dunn recommends.
Top tips for preventing summer scour syndrome
Implement a gradual weaning process
Promote rumen development during the pre-weaning period
Maintain the original housed diet alongside grass
Ensure calves have access to fibre such as straw, hay and silage
Add a buffer to the meal
Strip graze to encourage calves to eat the full stem
Avoid pastures which have recently had slurry or bagged fertiliser applied
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