Which is safer? Long Grass or Short Grass?
Many owners assume that long grass is automatically safer for a laminitis-prone or overweight horse - but that isn't necessarily true. Shorter grass does contain a higher percentage of water-soluble carbohydrates (WSC) than longer grass, but horses eat actual amounts of grass, not percentages. A horse grazing on long grass can take in significantly more per bite, meaning total WSC intake over an hour can end up higher on "safer-looking" fibrous long grass than on short. The real risk factor isn't grass length alone, it's total intake.
Jennifer Little BSc Hons MSc RNutr PgCert PgCert
Equinutrition® - Independent Equine Nutritionist, written 8.9.26
Why Grass Length Isn't the Whole Story
Horses evolved to be browsers, consuming a range of nutritionally poor but varied forages, including mixed grasses, plants and even certain trees and shrubs. They would cover large distances to find this varied but nutritionally poor diet on a daily basis. But fast forward to today and horses are more likely to be managed as grazers, with limited freedom to roam, grazing in fenced fields of nutritionally rich but variety poor grasses. This change of diet and lifestyle has meant that it can be easy for horses to over consume energy (calories) and become overweight or even obese, just from their grazing alone. Grasses provide calories in the forms of fibre, which in horses is converted into energy by the action of the bacteria within the hindgut. Calories are also provided by oils, protein and carbohydrates, including Water-Soluble-Carbohydrate (WSC), which are converted into body fat by a cellular process called de novo lipogenesis (DNL). WSC are the fructans and simple sugars that have been produced by the grass via the process of photosynthesis, converting sunlight into energy. These are made up of sugars, starches and fructans, which when consumed raise blood glucose and insulin levels. In horses if these are consumed in excess it can cause diseases such as obesity, Insulin Dysregulation (ID), Equine Metabolic Syndrome (EMS), and laminitis.
A horse’s sensitivity to WSC consumption and their risk of developing laminitis is influenced by several factors, such as being overweight and having conditions such as PPID (Cushings), ID or EMS. For horses at increased risk of laminitis, it is particularly important to control and limit the WSC intake from all feeds, forages and grazing. Controlling the WSC intake from bucket feeds and preserved forages such as hay and haylage, can be easier to achieve than with grass. As it can be difficult to know for certain how much grass is being eaten, how fast it is growing and (because of natural fluctuations) the WSC content within that grass. The WSC content within grass is affected by a range of factors including the seasons, the weather, the time of day and the rate of growth. The recent summer high temperatures and low rainfall have resulted in below average grass growth over the summer months, but this has been followed with moderate temperatures and rain fall, which caused rapid grass growth in the Autumn, as illustrated in figure 1. This has put horses that are sensitive to WSC at a greater risk of developing potentially fatal laminitis well into the Autumn months.
Figure 1: Seasonal grass growth (UK) 2025 & 2025 vs previous 5-year average [1]
If the amount of grass consumed is providing energy or WSC at an excessive level, then a change of management is required to reduce it. This can be achieved by several methods including, reducing the size of the field with strip grazing, reducing the time a horse is turned out, using grazing muzzles, or by increasing the energy requirement by significantly increasing the horse’s workload.
Another factor that affects the WSC content is the length of grass. As shorter grass contains a higher percentage of WSC and it is up to 25% more digestible than long, stalky grass [2], it can be easy for an owner to fall into the trap of thinking that longer grass must be ‘safer’ and short grass must be ‘bad’, but that is not necessarily the case. Because horses don’t eat percentages, they eat actual grams and kilograms and we don’t turn them out until they have eaten a certain amount of grass, we turn them out for a period of time. If grazing on long grass, a horse can take in a mouthful, or a larger amount with each bite than they could on short grass, where each bite can be reduced to a small nibble. Therefore, per hour grazing a horse could consume far more grass, calories and WSC on long grass versus on short grass, despite the longer grass being of lower nutritional value. Another way of thinking about it would be if we were wanting to reduce the number of calories or amount of sugar we were eating ourselves, we might opt for reduced sugar digestive biscuits (the longer grass) over a triple chocolate option (the short grass). But if we were to then eat three packets of the ‘diet’ digestives, we would be eating more calories and sugars than if we had only eaten two of the richer biscuits. Therefore, in a real life setting long grass is not guaranteed to be ‘safer’ for a sugar sensitive or overweight horse, and in some situations long grass could be considered less suitable.
This real-world scenario combined with above average Autumn grass growth rates, poses significant management challenges, especially for those horses at a higher risk of developing laminitis (overweight, ID, EMS or PPID). Regarding this group of horses, it is particularly important to monitor changes in weight, to prevent excessive body condition and manage grazing to control total intake. Care should be taken if horses need to be moved to rested areas with long grass, especially when so many current fields are parched and bare after the hot and dry summer, as this would result in a sudden increase in grass, calorie and WSC intake. Possible methods to control grass intake when on the longer grass could include the use of grazing muzzles, limiting either the time grazing or the available area with strip grazing. Regarding strip grazing care should be taken to avoid opening too large an area of longer grass. Consider moving a small number of fence posts into the rested area by only one or two stride lengths daily, rather than moving the whole fence line. In addition, if the grass is starting to regrow in the current area, consider stripping off a similar area as that which has been opened, to prevent the total grazing area from continuing to extend as the fence line is moved. Monitoring for changes in weight, behaviour or signs of ill health is vital in all horses, but especially during periods of change and for those horses at increased risk of laminitis. If you are unsure of the suitability of your horses’ diet you could speak with an equine nutritionist, but if you have any concerns regarding your horses’ body condition, sugar sensitivity, risk of laminitis or overall health please consult your vet.
References
[1] https://ahdb.org.uk/knowledge-library/forage-for-knowledge
[2] Geor, R.J., Harris, P.A., Coenen, M. 2013. Equine applied and clinical nutrition, health welfare and performance. Saunders Elsevier Ltd 332-335
FAQ’s
Is long grass safer than short grass for laminitis-prone horses?
Not necessarily. Shorter grass contains a higher percentage of water-soluble carbohydrates, but horses eat total amounts, not percentages - a bigger bite of long grass can mean more overall sugar and calorie intake per hour, even though the grass itself is less concentrated.
What is WSC in grass, and why does it matter?
WSC (water-soluble carbohydrates) includes the sugars, starches and fructans grass produces through photosynthesis. When consumed in excess, WSC raises blood glucose and insulin levels, which can contribute to obesity, insulin dysregulation, EMS and laminitis in sensitive horses.
How can I reduce my horse's sugar intake from grazing?
Strip grazing, grazing muzzles, reducing turnout time, and increasing workload to raise energy requirements can all help manage total grass intake. Introduce any reduction gradually and avoid opening large areas of rested, long grass all at once.
Does restricting grazing affect anything besides sugar intake?
Yes, it's worth remembering that grazing is also a horse's main source of dietary variety. Restricting turnout or forage intake to manage sugar levels can significantly reduce the range of plant fibres a horse consumes day to day, which matters for hindgut health as much as calorie control does. If your horse is on restricted grazing, it's worth reviewing whether their wider nutritional support is genuinely covering that gap, not just the sugar side of the equation.
Why does autumn grass growth increase laminitis risk?
A dry summer followed by rain and moderate temperatures can trigger rapid autumn grass growth - meaning horses at risk of laminitis may face elevated risk well beyond the usual spring danger period.
