Feeding the hot or fizzy Horse

Most horse owners have heard the terms ‘feeling their oats', ‘high’, ‘fizzy’, ‘hot’ and ‘hyper’ all used to describe the effect that grain or certain feeds seem to have on the behaviour of some horses.

Does feeding management or individual feed ingredients really influence the behaviour of horses?

Scientific research on the effects of feed or feeding management on horse behaviour is scarce. However, a basic understanding of feed and feeding management coupled with data from other animals may help to determine if a ‘calming feed’ actually exists or if it is just wishful thinking.

Feeding Management

The ‘natural’ diet for a horse is often far different compared to the performance diet for a horse. The ‘natural’ diet allows the horse free-access to pasture. Given this opportunity, the horse will graze for approximately 16 – 18 hours per day, assisting a slow, continuous intake of fibrous feed into the digestive system. Further, the ‘natural’ diet has the added advantage of the horses being able to roam around the paddock providing the horse with an ample amount of natural exercise. On the other hand, the ‘performance’ diet typically consists of two feeds per day to horses that are confined to a stable. These horses often finish their meals – that often consist of high-energy grain and limited amounts of hay or chaff - quickly and then stand for long periods of time waiting for the next meal, with little to no natural exercise. So what effect does the ‘performance’ diet have on the behaviour of a horse? The main features of the ‘performance’ diet are a low fibre intake, a small amount of time spent eating, a high grain intake and limited natural exercise. The combined result is an increase in stereotypic behaviours such as cribbing, wood chewing, weaving and stable walking. Many of these horses also exhibit excitable behaviour and scientists have tried to determine the exact cause or causes of these behaviour problems. Possible explanations include frustration due to confinement, lack of socialisation with other horses, acid accumulation in the digestive system as a result of a low fibre, high grain intake leading to pain, or simply a lack of exercise leading to pent up energy.

Formulating a more ‘natural’ diet

Some of the negative behaviour effects of the ‘performance’ diet can be alleviated by modifying feeding management. First, horses need to be provided with an adequate amount of forage. Horses require a minimum of 1.5% of their body weight in hay or pasture - for a 500 kg horse this equates to a minimum of 7.5 kg of forage. Horses will comfortably consume 2% of their body weight in dry forage (10 kg of forage for a 500 kg horse), and contrary to popular belief, providing adequate amounts of forage will not cause horses to become fat. Another management tool is to feed smaller meals on a more frequent basis, for example feeding three or even four times per day keeps horses occupied, alleviating boredom and frustration. It also slows the movement of material through the digestive system keeping the horse full and satisfied. Finally, giving horses an opportunity for turnout in a paddock or an arena will provide exercise and allow horses to expend pent up energy. Turnout for as little as 30 minutes twice a day will help keep horses mentally healthy and avoid negative stereotypic behaviour.

Dietary Ingredients

Several ingredients fed to horses have been identified by horse owners as ‘heating’ or having the potential to result in negative behaviour in horses.

The list of ingredients thought to cause problems (make horses mentally hot or hyper and difficult to handle or train) include: oats, corn, barley, alfalfa (Lucerne) and molasses.

Several possible explanations exist for why these ingredients may alter behaviour in horses. First, each of these ingredients contains a significant amount of calories and the negative behaviour may simply be a result of overfeeding calories to horses that are not adequately exercised. Since an overfed horse would have plenty of energy and they are not getting adequate turnout or forced exercise, they may channel the energy into negative behaviour. Starch and Sugar: A more scientific explanation for the change in behaviour may have to do with the sugar and starch content of the diet. Sugar and starch are found in large quantities in cereal grain and when it is digested in the small intestine of the horse the end product is glucose, which is absorbed into the blood. Fluctuations in blood sugar may be the cause of behaviour changes. Research has demonstrated that horses fed the exact same number of calories as either starch or fat had more spontaneous activity and reactivity to stimuli when fed a starch-rich diet compared to a fat supplemented diet. Does that mean fat is a non-heating ingredient or is it simply the fact that less sugar was fed to the fat-supplemented horses? Simply stated, more research is needed to answer this question, which brings up another interesting question. If changes in blood sugar cause behaviour changes then why do not all horses have behaviour changes when fed grain? The answer may lie in the fact that horses have large differences in their ability to digest starch and thus alter blood sugar. Serotonin: Another interesting theory for the reason certain feeds may cause behaviour changes revolves around the brain neurotransmitter – serotonin. It is important to understand that this theory has not been tested or studied in detail in horses, however for humans, serotonin functions to regulate mood - low levels of serotonin are often associated with depression. Thus, many human depression medications function to increase the level of serotonin in an effort to improve mood. In the human body, high levels of glucose from the digestion of starch increase serotonin levels. This improves mood, making humans more alert and active. So if attempting to apply this theory to horses, realizing this has not been thoroughly studied in horses, a picture may be painted that high starch (grain) diets result in high levels of serotonin and the horse feels good and becomes more active ie. thought of as ‘hyper’ ‘hot’ or ‘fizzy’. What about the protein in the diet making horses ‘hot’? Excess protein fed to horses can be metabolised and utilised for energy, however, protein itself does not seem to influence behaviour. The individual effects of amino acids, the building blocks of protein, have not been studied to determine their effect on mood or behaviour. Finally, many horse owners do not feel that feed influences behaviour at all and simply believe that a well-fed horse is displaying its’ normal or true behaviour. To change or modify this behaviour the horse simply needs to be trained so the energy is channelled into positive work rather than poor behaviour. In reality feed likely has the potential to modify behaviour, but there are several ways horse owners can minimise potential ‘heating’ effects related to feed and/or feeding management. Instead of feeding a diet that relies heavily on corn, oats and molasses, the diet can be modified to replace some of the grain with beet pulp, lupin hulls and soya bean hulls, so called ‘super fibres’ that stand out as low sugar, high fibre ingredients. Molasses in feed can be partially replaced with rice bran oil, an ingredient that does not contain any sugar. Feeding the grain concentrate portion of the diet in three meals per day instead of two meals per day may also help minimise large fluctuations in blood sugar. Finally, feeding a larger volume of good quality hay or pasture provides additional calories and helps minimise the amount of grain that must be fed to maintain body weight.

Calming Feeds or Supplements

There are several horse feeds and supplements on the market that claim to be ‘calming’ or ‘non-heating’ and horse owners are happy to purchase these products because of the potential benefit. Most of these feeds include low sugar ingredients such as beet pulp or other ‘super fibres’ such as HYGAIN® ICE® and in addition, they are supplemented with fat to provide non-sugar calories for the horse. Overall, these feeds generally contain lower sugar content, thus potentially resulting in less negative behaviour if fed correctly. Supplements that claim to calm horses typically have several common ingredients including thiamine and magnesium, as a deficiency of either the B-vitamin thiamine or the mineral magnesium results in nervousness, anxiety and even convulsions.

HYGAIN® SHOWTORQUE® is a high fat non cereal grain concentrate with elevated levels of Vitamin B. Typical diets fed to horses are rarely deficient in either thiamine or magnesium. Adequate research has not been conducted to validate the effectiveness of these supplements, although over-supplementation of the diet with these two ingredients does not result in toxicity issues. There are several herbal ingredients that may be used to calm horses; unfortunately, many of these are banned substances that cannot be utilised in the diets of competition horses. Care must be used in administering any of these products to horses. Although adequate research on the effects on horses of some supplements and certain feeds has not been conducted, it is known that feeding management and individual feed ingredients have the potential to reduce negative or ‘hot’ behaviour in horses - so there is hope for those owners and riders who happen to have one of these ‘fizzy’ horses in their paddock!