Trickle feeding: What is it and why is it so important?
By Ellen Chapman, founder of Trickle Net
We are all too familiar with the challenges of caring for horses through the cold wet and dark weather, but it’s during winter when our horses are most likely to exhibit stress related behaviours, often linked to restricted turnout and limited grazing.
Stabled horses are at increased risk of gastrointestinal disorders such as
colic and gastric ulcers. The causes can include a decrease in intestinal motility (movement of digesta) an unsuitable diet, and management practices which do not align with the horses fundamental need to trickle feed.
The horse has evolved to roam, browse and graze for approximately 18 hours a day, consuming a wide variety of different grasses, shrubs and course fibrous plants, in continuous small quantities whilst constantly travelling across miles of wild landscape. Under natural conditions, horses spend 60-70% of the daytime on feed intake, and 30-40% of the night time.
Horses do not voluntarily pause from feeding for more than 3 to 4 hours, and nor do they ever fast.
It is virtually impossible to keep our domestic horses this way. Common equine management practices often don’t allow for this feeding pattern or give the horse choice to roam and browse. Consequently, this disruption to natural feeding behaviour can lead to deleterious physical and psychological issues.
For improved welfare in managing our horses, we must seek to find the best solutions, considering both their natural environment and behaviour and adapting to provide suitable opportunities in daily management.
How horses eat
Trickle feeding begins with ingestion, and this starts at the lips. Horses have tactile, prehensile lips which manoeuvre with great dexterity to select and grasp grasses and forage or pluck tasty treats from hedgerows.
Have you ever had a horse nibble at your collar or find the zip on your jacket? Or root around for your treat pocket? Horses are mentally stimulated when they can exhibit this natural foraging behaviour, searching out small morsels of food.
Next, we come to the bite, enabled by the teeth. Horses have 12 incisors (6 upper and 6 lower) which are used to bite and tear stalks of grass and other forage from the ground, or from bushes and trees (or feeders and nets). Together with a natural twitch motion, the incisors extract an amount of forage determined by the environment, or by our method of feeding.
The horse’s cranial anatomy has evolved for the purpose of selecting forage, cropping small amounts of leaves or plant matter and passing this back to the premolars and molars which then laterally grind grass, feed and forage, breaking it down to small particles.
Equines have hypsodont teeth, meaning they have high crowns providing an excellent chew surface for abrasive plant material. Hypsodont teeth erupt continually throughout life (slowing down in old age) usually growing 2-3mm annually.
In their natural environment, this is balanced by horses consuming a far more stalky, gritty and abrasive fibrous diet, which is delivered at a steady rate through foraging and naturally grinds down the constant growth. The domestic horse eats a much softer forage diet. This means regular dental examinations are essential for rasping/reduction of the teeth due to unnatural wear and insufficient chewing/grinding which results in sharp points.
Digestion continues in the mouth with the addition of saliva. This is a crucial aspect to gastric health. A horse can produce 10 to 12 litres of saliva daily which is directly linked to the forage they consume. Saliva production is stimulated by the action of chewing, which lubricates the bolus of food/fibre.
The density of the fibre being chewed can also contribute to saliva production, with harder stalky forage producing more saliva than softer leafy forage simply because this takes longer to break down.
Studies have shown that the time spent chewing is the major factor for increased saliva production, rather than the chew rate. This means that providing opportunities for forage rations to be delivered over longer periods of time will support increased saliva production.
A one-way conveyor belt
Horses are non-ruminant herbivores. As opposed to ruminant species who have a multi-compartmented stomach and a return system for secondary chewing of ingested food (chewing the cud), horses are monogastric, having just one stomach.
Food bolus passes from the mouth to the oesophagus, which then pushes food down further with muscular contractions called peristaltic waves. At the entrance to the stomach is a one-way valve called the cardiac sphincter. This is an incredibly strong muscular ring which does not allow food stuff or even gas to return from the stomach.
This strict one-way digestive conveyor belt is perfectly tuned to trickle feeding on small constant amounts. Though this no-return system can be very unforgiving when the horse overfeeds or ingests harmful or inappropriate matter.
Their unusual gastrointestinal anatomy leaves horses prone to colic, where problems with matter occurring within the stomach cannot be regurgitated for relief. Horses cannot vomit or burp. Additionally, when the stomach is full or distended, it pushes back onto the cardiac sphincter valve, closing it tighter.
Choke in horses commonly occurs when a food bolus is swallowed which
is too large in volume, where there is insufficient chewing or food is too hard (eating too fast) or food is too dry due to insufficient saliva or inappropriate food (unsoaked pellets).
Food matter can become stuck at any point in the oesophagus, and the horse will exhibit muscle spasms as the peristaltic waves attempt to force the food along the tract. This can be quite distressing for the horse and the owner, and often requires a vet to dislodge the blockage. Ensuring an appropriate diet fed in a manner which provides a trickle feeding delivery can prevent choke.
A relatively small stomach
The horse’s stomach is relatively small, only about the size of a rugby ball in an adult horse. It holds between 8 and 15 litres. It’s at this point we need to consider the size of our feed buckets. A ‘standard’ feed bucket will hold up to 15 litres, meaning a large feed may easily fill the stomach; though the stomach works best when it is approximately half full.
The stomach lining has two distinct regions: the lower glandular region, equipped with a protective mucosal lining, where hydrochloric acid and enzymes are secreted to break down feed, and the upper non-glandular region, which lacks both glands and a protective lining, and does not produce acid or enzymes.
This anatomy supports the consistent, slow trickle of food intake. Saliva contains bicarbonate, which is an effective natural stomach buffer, neutralising the acidic environment to help maintain an optimum pH throughout the digestive tract, and protecting the upper non-glandular mucosa. If a horse is constantly chewing and consuming a natural trickle of forage, this enables an ideal environment for digestion and prevents the build-up of excess gastric acid.
The food consumption rate of any equine is fundamental to gastric function. If too much foodstuff is consumed too quickly, the stomach fills above the glandular area into the non- glandular area, allowing hydrochloric acid to reach this sensitive tissue which can cause irritation and potentially become ulcerated and painful.
Conversely, if the horse does not consume enough forage, this may lead to an unnatural increase in gastric acid which also brings a high risk of pain and ulceration.
The stomach empties regularly, passing the food bolus into the small intestine, which is responsible for the initial absorption of sugars, starches, proteins, and fats through enzymatic digestion.
Food moves through the small intestine quickly (1.5 hours) and this efficient process provides optimum absorption of nutrients with a constant trickle of matter. Following this, food passes into the caecum, where microbial fermentation begins. These microbes break down fibrous plant material, producing essential nutrients and energy.
A constant trickle of fibrous feed in to the caecum means it fills gradually. When full, it triggers the release of small amounts into the colon where fibre digestion continues through microbial fermentation, while also absorbing water.
Rather than eating until their stomach is full, horses need to eat small amounts continuously until their caecum is full to ensure optimum hind gut function and fermentation.
Feeding large amounts can be counter-productive in terms of the feeding goal. Research has shown that improved nutrient digestibility is achieved by feeding smaller more frequent meals. It is thought that the decreased passage rate of digesta through the gastrointestinal tract with slower transit times gives more exposure to enzymes and microbial fermentation for longer periods.
Effect on blood glucose
Another important benefit to feeding our horses at a natural rate is the effect on blood glucose. Meal frequency will influence blood glucose and insulin concentrations in horses, and smaller more frequent meals are beneficial - especially for horses with metabolic disorders who need to maintain low blood glucose levels.
Horses who are subject to inappropriate diet and management may be at risk of insulin dysregulation when obesity starts to change the normal function of cells and hormones.
Stress-related behaviours
Horses are highly motivated to eat. In addition to their physical function, they have a psychological dependency on trickle feeding. It is a high priority of every equine to take in roughage continuously to ensure good behavioural, physical and mental welfare.
Chewing for prolonged periods of time supports a healthy digestive system, though trickle feeding (grazing) also releases endorphins in the horse, reducing stress, improving mood and supporting a calm, happy herd life.
Modern management doesn’t always allow for trickle feeding, and horses can exhibit stereotypical behaviours when natural behaviour is suppressed. A large number of studies have found direct links between the absence of consistent feeding and stress related behaviours such as cribbing, weaving, wood chewing and box walking.
Non-edible bedding
One significant change in modern horse management is the growing popularity of non-edible bedding. The range of shavings, wood fibre and unpalatable plant bedding is extensive, and brings benefits in convenience, storage and absorbency.
However, the absence of edible roughage in the form of straw bedding is shown to bring negative behavioural changes in horses.
A study in Germany looked at 104 horses, stabled side by side on edible and non-edible bedding. It was found that horses on non-edible bedding finished their hay meal faster, and took fewer pauses during eating. The majority of these horses had finished their forage by midnight, and the average nocturnal feed intake interruption was 9 hours - far exceeding the maximum tolerable pause of 4 hours and presenting a risk to welfare.
Another study found that horses kept on straw express less aggressive behaviour compared to those living on non-edible bedding. Could the decline in straw bedding be linked to the increase in EGUS diagnosis?
The right balance
The balance between providing the correct amount of forage and also providing enough chew time is particularly important, and it’s here that we must seek the most beneficial delivery of forage within the horse’s management and environment.
Horses require 1.5% to 2.5% of their bodyweight in dry matter per day, depending on the feeding goal. Overweight horses and ponies are often restricted to 1.5%BW on vet’s instructions to prevent or manage laminitis. It is crucial to supply this forage over the longest time possible to enable optimum function of the gastrointestinal tract, preventing both physical disorders and psychological distress.
Though it’s not just overweight horses who require this consideration. All
horses need access to a near constant supply of forage, delivered at a species appropriate rate to support optimum gut function and overall wellbeing.
Given the high prevalence of EGUS in performance horses across all disciplines, there is a clear need for improved dietary management and understanding. While some treatments look to supress acid, it could be that a simple management change in providing trickle feeding opportunities to sports horses is the most effective performance enhancing solution possible.
