Effects of Spring Grass on Horses

Effects of Spring Grass On Horses

After such a wet winter where our fields in the UK have either been literally underwater, covered with surface water or a mud bath, it’s tempting to increase turn out for your horses at the first sight of green grass. Luxurious spring grass, nature's way of restocking important nutrients after the ravages of winter, is exceedingly tempting. Plus this abundance of grass coincides with the natural foaling season, providing mares with the high levels of protein and calories they need to support milk production. However as lovely as it is to see the majority of fields actually looking green again rather than brown, this change in grass composition causes all kinds of challenges for horses and owners. And we’ve all seen it – after a few weeks of milder weather, our horses seem to magically grow invisible springs on their hooves. Read on to find out why…

What are ‘Fructans’?

The reason why your horse becomes a monster for a couple of weeks a year is down to powerful soluble carbohydrates in the grass called ‘fructans’. Fructans are a type of sugar that is a by-product of photosynthesis and is used to aid plant growth. On sunny days, ‘fructose’ is produced in large quantities and stored within the blade of grass which is why grass is at its most sugary when it starts to shoot up in the spring time. When it cools off at night, these fructans are then utilised as fuel for growth.  

Fructans are higher in the seasons when the weather is cool: spring and fall. They are still present during hot summers, but not usually at levels that can be dangerous. 

How do ‘Fructans’ affect horses?

Fructans are a non-structural carbohydrate that horses cannot digest. They’re broken down by the microorganisms in the equine hindgut first so that they can be absorbed. Horses love to eat grasses that are high in fructans. Those that are unaccustomed to grass turnout, that have been on hay all winter or that are already prone to colic and laminitis can have their digestive tracts upset easily by high levels of fructans.  

Seven key facts you need to know about Fructans

It’s higher:

1) in over grazed fields than in lush grass

2) when night-time temperatures drop below 40 degrees because the grasses do not grow, so the excess remains stored in the stems

3) in mature grass that’s 8-10 inches long

4) in the afternoon/evening on a sunny day.

It’s lower:

5) in new spring grass that’s 3-6 inches long

6) in the morning when days are sunny and nights warm

7) in rainy wet weather.

Top tips you need to know for the sake of your horse’s health:

1) Increase spring turnout gradually

2) Turnout in the morning or late at night

3) Limiting the number of hours of turnout may be counterproductive, your horse will get wise to the regime   

4) Don’t let the grass get longer than 6 inches

5) Don’t overgraze your fields, rotate them to give them a break

6) Beware of Jack Frost, sunny frosty mornings are common at this time of the year

7) Use a grazing muzzle, these are scientifically proven to reduce the grass intake

8) Restrict the grazing area with temporary fencing.


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Kim Horton

Co-Founder of EQUUS and a keen equestrian, when Kim's not at her desk she's with her horse, Waldo.


  • Lisa Groves posted on March 06 2020 at 10:03 AM

    Thanks for all your informative blogs. I’m forever learning!!

  • Teresa Watts posted on May 20 2020 at 12:05 PM

    Help, my normal easy to catch ID is now no longer letting me get near him never mind putting a head collar on just prances off trotting and cantering almost taunting me, will sometimes let me get to him then sees the head collar and bobs off, he normally comes to me no issues coukd this be the Spring Grass? #witsendhorsemum

  • Andrea Deane posted on March 08 2021 at 09:03 AM

    Very interesting thank you x

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