Horse Husbandry: Nutritional Requirements

This essay is going to evaluate nutritional requirements when feeding horses to prevent or manage impaction colic, laminitis and obesity. Horses (Equus caballus) are non-ruminant herbivores that graze throughout the day. As this species has a small stomach there is a limited amount of food that can be eaten before changes occur within organs, leading to many health issues.

Obesity, the excessive accumulation of fat, can be noticed easily when examining the body. Muscle and bones being hard to see are signs of this. This is a common issue in equines which makes them susceptible to further health problems such as laminitis and colic. Ponies, which are below 14.2 height in hands, have evolved to survive on a fibre-based diet of rough plains. However, due to the extra feed that is provided by owners, which contains additional calories, the animal can quickly and easily become overweight if their diet is not monitored alongside their exercise levels. Recent studies have shown this is a common issue in all ponies, even those that are thought to do a lot of exercise.

A perfect exact body weight is difficult to determine due to affecting factors such as the age, breed, height and fitness levels of the organism. For example, it is thought 12hh ponies should weigh 230-260kg whereas 14hh ponies should be 320-380kg, but 360-450kg for a 14hh cob pony. Body scoring, along with weighing, is a suitable method used to get an overall condition of the animal. A weigh-tape is used by wrapping it around the pony’s body, running over the highest point of the horse’s withers, in the same place each time to get a measurement. This scoring assesses different areas of the body to examine physical condition by looking at the fat proportion and can help maintain a healthy weight. In the UK a 0-5 system is used with 0 being emaciate, 3 being a healthy weight and 5 being obese. This gives a good perspective on the overall condition of the animal.

The main cause of this health problem is diet. Horses and ponies require a high fibre low sugar diet, but due to the amount of additional feeds that are available, which all have a different calorie and vitamin quantity, this makes it difficult to maintain their weight. They are overfed on sugars and get too many calories for the amount of exercise they do, so do not use up this extra energy which then turns into fat.

Laminitis, a common vascular disease, can cause permanent damage to equines hooves affecting any four feet, but mainly seen in the front two hooves. It is inflammation and damage to the soft tissue structures that attach the pedal bone of the foot to the hoof wall (laminae). This inflammation leads to instability of the pedal bone in the hoof and in more severe cases, separation of and rotation of this bone within the hoof wall can occur. This disease can disrupt the blood and oxygen to the laminae which causes this part of the hoof to die, leading to the rotation of the bone since the attachment gets weaker.

For acute laminitis, symptoms usually occur very suddenly and includes unwillingness to move, lameness and leaning backwards to relieve pressure from its front feet. Whereas for chronic laminitis, which is when the signs have been showing for 48 hours, ongoing symptoms will be shown. An example of this is the hoof having an appearance of growth rings around the hoof wall which indicates a previous attack of this condition.

There are many causes of this condition, but more commonly it is due to a high intake of soluble carbohydrates. Grass needs light, to make sugars, and a temperature above 5°C to grow. If the conditions are suitable for making sugars, but not grow, then these extra sugars are stored as fructan. Due to this, laminitis can occur year-round and not just in spring, as it was thought previously thought. Fructan is a component responsible for this disease. As horses are unable to digest this in the stomach and small intestine it is passed into the hindgut where it is fermented by bacteria. Starch, which is stored in cereal grains, is absorbed in the small intestines, but when too much is eaten it passes to the hind gut where that too is digested by bacteria. However, the excess fructan and starch that enters the gut results in the gut becoming more acidic and some beneficial bacteria dying (Bailey et al, 2014). Then due to an overload of these soluble carbohydrates, a release of endotoxins enters the bloodstream through the damaged gut wall which occurs due to less beneficial bacteria being present.

Impaction colic, which is defined as abdominal pain, is caused by a blockage in the large intestine, usually by a build-up of solid material, which prevents food passing through the gut. This common health problem can be life threatening to horses with it being one of the main causes of death. Some symptoms of this includes sweating, kicking or biting the stomach, rolling or laying down excessively and refusing to eat, but it is not certain that an animal has got colic until seen by a veterinarian.

To prevent and manage impaction colic, the horse must be on a strict diet that reduces the change of a blockage. Whereas for laminitis and obesity it is to reduce the amount of sugar and starch that is digested. Factors influence how prone an animal is to being affected, such as age and breed. For example, studies have shown that thoroughbreds are of highest risk of getting colic. Compared to older individuals, which are more prone to being overweight with laminitis signs due to their activity levels decreasing.

Owners care for their horses in the best way possible, however sometimes more harm than good is caused. If a horse’s energy levels decrease but their diet is not altered then this can quickly lead to health issues. Similarly, if they are no longer in work, for example, their owner may be less strict with treats which will see the same results. A UK study showed 61% of horses were reported to have a decrease in the intensity of exercise in older individuals and therefore the health problems became more common with age. Colic was the overall leading reason for admission to a veterinary referral hospital of horses 20 years old and above, laminitis was the next most common issue. Here, supplements made up a part of their diet, but this did not stop them becoming ill. This suggests supplements do not always work alone and the rest of their diet needs to be looked at too. Another UK study on horses 15 years old and above resulted in 18.6% being lame on a walk and 50.5% being lame in a trot. Also, 83.5% had a reduction in motion range in at least one joint which is a laminitis sign. Many of the equines in these surveys were overweight, suggesting this is also common in geriatric horses. However, individuals of any breed and age can be affected by these issues so they should all get fed a suitable diet for them to be prevented.

Furthermore, for horses that are in hard work they will require more food and a higher calories intake as they us up a lot of energy. Whereas for older horses their calorie intake should be reduced due to the limited exercise they will have. Additionally, if the pony was needing to gain weight then a chaff that does contain more calories can be useful, but a risk of laminitis comes with that. An underweight pony with laminitis can be fed digestive enhancers, such as Baileys Digest Plus. which encourages the use of existing useful bacteria in the gut. Additionally, the percentage of food intake would alter depending if the aim was to lose or maintain weight.

As forage makes up the majority of the horse’s diet, a dramatic change in this can have a more severe effect on the body resulting in any of these health problems. Either changing the batch or type of the food, turnout time, or the quantity and frequency of feeding can influence the animal’s health. So, it is recommended that a change occurs slowly to allow time for the body to adapt rather than suddenly. Adjustments to feed changes can take a minimum of 3 weeks, so to allow the gut to adapt these changes should be made slowly over a 2 – 4 week period. Regularly changing the turn out time would impact the animal’s health as grass has a different nutritional value at different times throughout the day, due to the conditions it can grow in. Therefore, if the horse regular had more sugar, but their concentrate or balancer was not changed to accommodate this then this is when laminitis could show.

Not starving the horse but feeding little and often throughout the day is the best option. Large meals increase the amount of soluble carbohydrates that go into the hindgut, as the food moves quickly through the digestive system. A large consumption of concentrates, or a small quantity of feed but with a high sugar content, increases the risk of these conditions due to the excess going through the gut. Therefore, the maximum individuals should be fed each meal is 0.4kg per 100g bodyweight, but each brand has its own specific recommended weight. If the organism was to be starved, then every time they have access to food this would lead to overeating in that period as they are unaware of how long they would have to go without eating again. Also, if the feed was reduced in an attempt to lose weight, then gas bubbles that have formed will accumulate leading to a blockage and causing impaction colic. Furthermore, the animal should be fed according to their workload so the correct amount of energy is gained to match what has been used.

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One study showed a high fibre diet resulted in the majority of individuals getting colic due to this absorbing water. However, other studies showed a decrease of the risk when fed on a high-fibre diet only getting forage or grass. This shows that it is the diet which has a massive affect on if the horse gets colic or not. Implying outcomes can change depending on what other foods are being fed alongside the main feed. These studies also suggest it is due to the workload of the animal that changes the outcome too, with if little work is done a high fibre diet is not suitable.

Also, some roughage should be restricted due to this being hard to digest. Although grass is easy to digest it does not offer as much fibre than hay or haylage. Therefore, if feeding hay a soft and digestible one should be chosen to prevent colic. Haylage is typically more digestible making it the better option and is high in fibre. Moreover, hay can be soaked before giving as a feed. This can reduce the sugar quantity, the same as for laminitis or obesity, but this also increases the water intake which reduces the chances of dehydration. A different option to hay that can be fed is haylage. This is moister therefore offering extra water to prevent blockages. Also, salt can be given in one of the feeds to encourage drinking. A further way in which these conditions can be avoided is by using hay nets with smaller holes, this will lead to it taking longer for the horse to eat.

At periods of high risk of laminitis or colic, digestive enhancers such as Baileys Digest Plus can be given. These help useful bacteria grow to prevent more insoluble carbohydrates entering the bloodstream through the damaged gut wall. As the small intestine is where sugar and starch are digested and absorbed, these levels need to be kept as low as possible. Soaked high fibre feeds, such as fibre-beet is an example of feed to help minimise these conditions. Oats are digested easier, due to the simple starch structure, compared to cereal. However, when on a cereal feed the diet is made up of much forage too which can still lead to colic. Although, most cereals are cooked which minimises the chances of any starch spilling into the hindgut and causing either impaction colic or laminitis.

It is recommended for a horse or pony to eat 1.5% of its body weight per 24 hours, but 1.3% if laminitic. The amount and type of feed that the animal gets depends on their weight, height, age and workload. An example for a 6-year-old 12hh laminitic Shetland pony, what is in light work and weighs 300kg, is for 3.90kg of feed with an additional balancer or supplement to be provided per day. This is spread out over four feeds which 2/3 is hay and 1/3 is low energy chaff, as shown in the ration below.

Hay Low energy chaff Balancer

Morning 1kg 175g

Noon 1kg

Afternoon 0.30kg 10g of salt

Evening 1.60kg 125g

Although forage, which makes up the majority of the diet, can be essential for a healthy gut function, it contains many calories. This can mean the weight is not managed if the rest of the feed is unsuitable. As part of this ration, access to grass should be restricted to limit fructan intake to help with managing the health conditions. Then when some weight has been lost, grass can be slowly reintroduced. After weighing the hay it should be soaked to remove the sugar and energy content, especially since the pony is laminitic.

As chaff must be fed in larger quantities to get enough nutrients, it is essential for one with less calories to be used. This is given with the concentrate to slow down the time it takes for the equine to eat. Baileys Light Chaff, which is high in fibre but low in calories, starch and sugars would help to lose weight as well as to manage laminitis. Additionally, the importance for a low sugar content is necessary for the same reason. As more chaff is required to get enough nutrients a large feed is a must. However, this still increases the risk of laminitis due to the excess carbohydrates entering the bloodstream.

There are many different balancers that can be used when ponies are overweight, such as Dodson and Horrell ultimate balancer and TopSpec Comprehensive Feed Balancer. Since the majority of balancers are guided to feed the same amount (100g per 100kg of the body weight) it is the nutritional value that differentiates them. One that could be used in this example is Baileys Lo-Cal Balancer. This is suitable for ponies in light work, are restricted to grazing, and prone to laminitis. The benefit to this balancer is there is a higher vitamin number of protein and fibre percentage, which is essential due to those that are lost from not eating grass, and lower starch and sugar percentage compared to other brands. So, as well as getting the needed nutrients, overload of starch and fructan is limited which helps to decrease the weight, taking less pressure off the limbs and reducing extra sugars from entering the hindgut. It also means less food is required to get enough nutrition, which helps with managing the weight and preventing laminitis. This specific feed is also beneficial as it can be suitable for geriatric ponies. This reduces the chances of getting any of these health problems further with there not being a major change in the diet.

Moreover, supplements can be used rather than a balancer. However, although it is recommended by companies it is believed that this is not the best option. This is due to many being high in fat which does not help with the weight loss. Additionally, some supplements have a high molecule size which does not absorb as quick, making it easier to get blocked which can cause further issues such as impaction colic.

Overall, equines require a strict diet to ensure they get the correct nutrition level. If this is not stuck too then many health problems such as obesity, laminitis, or impaction colic can be a result, leaving the animal in pain. However, there are many ways to prevent this with a range of feed options that can be picked from. Although they have certain requirements it also depends on the individual horse to what is best for them, not every option will work for every animal.