Grass Laminitis by Liz Craigie, MSc, Nutritionist at Norvite
The days are stretching and the weather is getting warmer. Day by day we see the countryside getting
greener - the grass is really growing now. For those owners of ponies and native bred horses the annual
priority of pasture and feed management to avoid laminitis is coming to the fore. Some may already have
had their first laminitis incident of the year.
We have to return to the origins of the horse to look at what might be causing laminitis in our modern
day management system. Horses evolved in a number of environments, most of them quite harsh. The
British natives evolved to graze the uncultivated forage of mountains, moors, heaths and downlands.
The herbage was varied with grasses, herbs and shrubs but generally of poor quality. The herds would
graze vast areas to get all the nutrients they needed.
Our modern management involves restricted grazing on improved pasture. The plant variety is not so
varied but the concentration of nutrients is much greater. Grass varieties such as ryegrass have been
developed to give high yields of energy and protein. Traditional varieties are still used in some pastures
in the aim to minimise poaching. Grass mixes can be selected to specific purpose including native pony
grazing but in the majority of cases it is selected to maximise productivity. Grass and plant species will
vary with soil type, drainage, age of the sward and fertility of the ground.
Still the question has to be “Why does the field my pony grazed all winter suddenly provide the wrong
nutrient balance and pose a risk to his health?”
Links have been shown between high starch diets or a move to high energy legume diets in the cause of
laminitis. Fructans, a soluble carbohydrate produced in grass are now a key focus.
Legumes and Nitrogen
The most common legume in horse pastures is clover. It is a key nutrient source for ponies but the
sudden growth in the late spring can result in a rapid increase in the protein content of the diet. Clover
growth is slightly slower than grass, it is at its greatest in July and August. As the season progresses your
pony will naturally eat less clover as it becomes bitter to taste and therefore less palatable.
If grass is grazed short the clover has more opportunity to compete for space and may become more
dominant in your sward than intended. A maximum 40% of your pony’s grazing area should be clover.
Clover levels are limited when the grass is not grazed below a length of 4-6cm. Application of Nitrogen
fertiliser will also inhibit clover productivity.
Equines have developed to cope with a normal level of what are potentially toxic compounds referred to
as Non-Protein Nitrogen (NPN) in their forage. The level of these compounds is higher in the lush spring
growth of fertilised, improved pasture. Clover under stress such as frost or drought will also accumulate
these compounds naturally. Certain weeds also act as nitrogen accumulators and a fourth source of
NPN is the direct consumption of fertiliser. At excess levels these compounds overload the digestive and
metabolic system of the horse causing liver imbalance and toxins in the blood. Toxins in the blood may
trigger laminitis.
Sugars, carbohydrates and fructans
Fructans are water soluble fructose polymers ie simple sugar complexes made from fructose molecules.
These compounds are made by actively growing plants to capture the energy of the sun making the
energy available for growth. The plant gathers the fructans at its key growth areas. In the early spring the
plant’s focus is the growth of leaves to capture as much sunlight as possible, fructans therefore gather in
Norvite, Wardhouse, Insch,
Aberdeenshire. AB52 6YD
Telephone: 01464 831261 Fax: 01464 831400
the leaves. Later in the season the plant focus changes to reproduction and the fructans are transported
from the leaves to the emerging flower-heads.
If the plant is able to grow at the optimum speed the fructans will not accumulate as they will be used
to produce the new growth. If nutrient levels are restricted limiting growth or other factors such as frost
after sunny days cause plant stress limiting growth, the fructans will accumulate until the growth is reestablished.
With all horses and particularly our laminitic ponies we are careful year round with carbohydrate intake.
Excess water soluble carbohydrate is known to be a laminitis trigger. This non structural carbohydrate
must be digested in the pony’s small intestine. From here the nutrient can be taken into the blood stream
and used by the horse. Carbohydrate reaching the large intestine or fermentation vat of any horse should
be structural otherwise known as fibre. The micro-organisms of the large intestine ferment this fibre to
release energy and protein.
If soluble carbohydrates such as sugars and starches reach the large intestine they can cause digestive
upset. The fermentation changes which affects the bacterial population and may result in lactic acid
production. The result may be acidosis, colic or laminitis.
Fructans are soluble carbohydrates but unfortunately cannot be digested by the horse in the small
intestine. All the fructans consumed will therefore arrive at the large intestine resulting in the negative
type of fermentation, potentially triggering laminitis if supply is not controlled.
How can I manage my pony and pasture to limit the risk
Being aware that your pony may be at risk is vital. Overweight ponies, those that have had laminitis
before and good do-ers would be the “classic” victims of the disease. However, management to prevent
laminitis infact involves good horse and pasture management and is not going to negatively affect any
animal. The focus should be on maintaining the condition of your animal and good pasture care.
The management of the pony to minimize the risk of laminitis is a year round task. It is important to keep
your animal in its ideal body condition throughout the year, not just the key laminitis seasons of spring
and Autumn. It has been shown that a pony experiencing excess weight at any time during the year is at
greater risk of laminitis. Weightape your pony regularly to monitor any fluctuations. You should be able
to feel the ribs when you stroke the side of your pony but not see them when you step back.
It is important not to starve your pony. Fasting actually increases the susceptibility of animals to the
effects of sugar. Make sure your pony gets at least 1.5% of its body weight a day as roughage. Ideal for
this is hay that was made after the grass had flowered or bagged fibre feeds including alfalfa but low or
no molasses. Try to give part of any bucket feeding prior to turnout.
Fructans are most concentrated in grasses under stress. Stress can be caused by any environmental
factor that restricts potential growth while the sun is providing the energy to produce sugars excess to
requirement. These stress factors include temperature drops to below 5OC, lack of nitrogen or lack of
water which is are essential nutrients for growth.
Calculate how much fertilizer your grazing area needs. Use a balanced fertilizer containing N & P, some
experts would recommend limiting the amount of K (potassium) in the fertilizer as an excess can affect
magnesium availability. Allow the grass to grow at its optimum level the concentration of fructans per kilo
of grass will be less but the amount of grass in the area will be greater.
Restrict the daily intake by your pony through the use of electric fencing and a strip grazing system. This
will allow you the greatest control over intake. Opening up a new section of grass daily will allow access
to fresh clean grass. Once the restricted grazing area is big enough to allow your pony to stretch his legs
in a canter use a second fence to block the same area behind the grazing as you open up at the front.
This then allows controlled grazing, freedom to exercise and a re-freshing of the pasture.
Norvite, Wardhouse, Insch,
Aberdeenshire. AB52 6YD
Telephone: 01464 831261 Fax: 01464 831400
Protein and NPN management of your pasture is again linked to the fertilizer policy. Fertilizer can be
used to manage the clover levels in your pasture. Rotation of the pasture to allow periods of rest is an
important part of any pasture management plan. Fertilizer should be applied as the horses come off
the field. This should ensure that the horses do not come into contact with “raw” fertilizer. Rain will
soak the fertilizer into the top soil making the nutrients available to the grass. Ask your local supplier
for help in developing a fertilizer program..
Key tips to manage your laminitic
Strip graze
Clear paddocks of dung – daily if possible
Choose grass mixes specific to the task
Develop a fertilizer policy to optimize grass growth
Fertilise ground at the start of a rest period
Aim to manage clover production
Buffer feed using hay or alfalfa
Norvite, Wardhouse, Insch,
Aberdeenshire. AB52 6YD
Telephone: 01464 831261 Fax: 01464 831400