All about Starch
Read any article regarding equine digestive health and you will be advised to feed a low starch horse feed. But what is starch, why do we feed it to horses and why do we need to be careful with high starch horse feed?
What is starch and where do we find it?
Starch is a carbohydrate and storage form of energy for plants. Plants store varying amounts of starch and it is typically found in much higher concentrations in the seeds or grains of cereal plants. Oats, barley, wheat and maize are the cereal grains most commonly used in horse feeds and contain high levels of starch. Grasses and alfalfa would typically supply 2-3% starch, compared to cereal grains like oats that supply in excess of 50% starch. Interestingly, alfalfa stores the sugar it produces as starch but it moves it into its roots which is why the parts that are used in horse feed are so low.
Why do we feed starch to horses?
Traditionally starch in horse feed has provided a concentrated source of energy that horses find very palatable. Horses that are working very hard have high energy demands and as forage has a low energy density a lot would have to be consumed to meet the horse’s needs. There are ways around this such as pelleted forms of high-quality fibre such as Alfalfa Pellets and using oil alongside the fibre which are becoming more popular alternatives to cereals.
Starch is broken down in the horse’s small intestine to the simple sugar glucose which is a readily available source of energy for the horse. When produced in excess of the horse’s immediate energy requirements, glucose is stored as glycogen in the horse’s muscles and liver. Having a sufficient store of glycogen is particularly important for the performance horse, like the racehorse, as when they are working at fast speeds their body uses anaerobic metabolism to break down glycogen to glucose to use for energy. Insufficient glycogen stores will limit performance and result in fatigue. Starch from cereal grains tops up the horse’s glycogen stores faster than other energy sources such as fibre, which may be particularly significant for horses that are competing with little rest time between competitions. It is interesting to note that compared to humans, horses are quite slow at replenishing their glycogen stores regardless of the energy source.
Why do we need to consider a low starch diet for horses?
Firstly, as the amount of cereal based feeds in the diet increases, typically the amount of fibre offered or consumed decreases. Fibre is vital for the maintenance of digestive health and digestive disturbances, such as gastric ulcers and colic, are more likely to be experienced in horses on a low fibre, high starch diet. Secondly, horses have a limited capacity to digest starch in their small intestine. Starch escaping digestion in the small intestine ends up in the horse’s hindgut where it is rapidly fermented. This results in a more acidic environment and a change in the intestinal microbiota. This change has also been linked to an increased risk of colic, laminitis and even behavioural changes.
When feeding starch to horses we therefore need to be mindful of the amount used and consider whether, for horses in lower levels of work, we actually need to feed cereal based concentrates at all. If too much starch is fed, then the risk of digestive disturbance increases. Current advice is to restrict starch intake to less than 1g of starch per kg of bodyweight per meal and less than 2g of starch per kg bodyweight per day.
Click here to use our Starch Intake Calculator to ensure you are feeding the correct amount of starch to your horse.
What’s the alternative to starch for horses?
How can we strike a balance for hard working horses that have high energy demands between meeting their energy needs whilst looking after their digestive health? As a starting point use more digestible sources of fibre such as early cut haylage, alfalfa and sugar beet, as these can provide significantly more energy than less digestible fibre sources such as late cut hay. Oil is also a useful addition to the ration as it is very energy dense. Dengie Alfa-A Oil combines highly digestible alfalfa with a rapeseed oil coating and supplies as much energy as a competition feed, but without the starch. Only then, if energy demands cannot be met as the horse is working very hard with limited rest between competitions, should a high starch horse feed be considered and care taken not to exceed recommended levels.
For feeding advice on low starch diets for horses contact the Dengie Feedline on 01621 841188 or complete our Feed Advice Form.