Wednesday, June 5, 2013

The Importance of Species Appropriate Feeding and Eating Behaviour of Horses

by L.D.

Unlike the human’s digestive system, the horse's digestive system is designed by Nature to receive food in small portions almost constantly, day and night. By locking horses in stalls and making their feeding schedule similar to that of a humans — very few meals a day with long breaks in between — humans ruin the horse's organism, making the animal suffer from pain caused by the health disorders it develops as a consequence of the unnatural feeding schedule, such as gastric ulcers, colic, etc. In order for your horse to stay healthy and happy throughout its life, it should be provided species appropriate keeping conditions, which means conditions that are as close as possible to the natural way of life of the horse. This means all horses should be provided 24 hour access to grazing or/and hay, should be provided the possibility of unrestricted free movement 24 hours a day (the 'open stable' system) and be able to live together with equine companions. Now let’s take a scientific look into the importance of species appropriate feeding/eating behavior in horses.


This article focuses on the importance of species appropriate feeding/eating behaviour of equines. However, as also mentioned in the five freedoms (Farm Animal Welfare Council, 2009), which are building the base of the animal rights and protection, other factors are crucial in order to guarantee the well being of the horse:

1. Freedom from Hunger and Thirst — by ready access to fresh water and a diet to maintain full health and vigour.
2. Freedom from Discomfort — by providing an appropriate environment including shelter and a comfortable resting area.
3. Freedom from Pain, Injury or Disease — by prevention or rapid diagnosis and treatment.
4. Freedom to Express Normal Behaviour — by providing sufficient space, proper facilities and company of the animal's own kind.
5. Freedom from Fear and Distress — by ensuring conditions and treatment which avoid mental suffering.

Not only species appropriate feeding, but also being free to express species appropriate behaviour, such as herd-life, movement, mutual grooming and more, are of utmost importance and need to be fulfilled in order to guarantee the health and well being of the horses (and any other animal).

Scientifically speaking, equines are herbivore hind-gut fermentors. Having evolved to almost constantly eat little portions of long, rough fiber being low in energy. Observations and researches showed that horses being free to choose their feed stuff spend approximately 60% (~14 hours) of the day browsing and grazing (Gudmundsson and Dyrmundsson, 1994; McGreevy, 2004). Horses in a scarcer environment spend approximately 16–17 hours per day browsing and grazing, which may even exceed 19 hours in harsh seasons (McGreevy, 2004). However, the time spent eating strongly depends on several factors such as weather conditions, availability of feed stuff, gender, state of maturity and more. (Gudmundsson and Dyrmundsson, 1994).

Given the possibility to free range and express species appropriate eating behaviour the horse will consume approximatly 2–2,5% Dry Matter of their body weight within 24 hours, in the form of roughage. (National Research Council (U.S.), 1987; Kiley-Worthington, 1987; Dowler, et al., 2009; Wright, 1999).

Being able to free range and spend most of the day grazing results in approximately 57000 chewing movements (Cuddeford, 1999) on high fibre roughage (and about 40000 on roughage with an average fibre content, which in this research is the more likely number to work with) (Frape, 2004). Figures as such are often critically questioned as they are mainly derived from researches and observations from wild, feral or semi feral equines, however the genetic make up of ingestive related behaviour/instincts and physiology of the digestive tract have remained relatively unchanged over the last 6000 years of domestication and breeding (Koene and Gremmen, 2002; Dierendonck, 2006), which is then directly linked to the high occurrence of health and behaviour problems due to inappropriate nutrition.

The same eating behaviour performed by free ranging horses can be seen in domestic horses when given the possibility to execute this normal and instinctive behaviour (Kiley-Worthington, 1987). However, most domestic horses, nowadays, are only able to express limited normal eating behaviour due to human management. For example concentrates in the form of pellets, muesli or oats are fed in restricted meals with or without limited amounts of pre-cut hay or haylage. This change of feedstuff also manifests a change of eating behaviour in terms of eating time, chewing movements and, importantly, saliva production.

A horse being free to graze adequate mature pasture, 24/7, will consume an approximate Dry Matter intake of grass of 2 Kg per 100 Kg body weight per day (600 Kg horse). When being limited in grazing the horse will consume approximately 0,8 Kg DM of grass in one hour. The horse given limited hay at specific feed times will spend approximately 40 minutes per 1 Kg of hay, resulting in about 1,2 Kg Dry Matter intake per hour (Ellis, 2004). When given hay ad libitum it is most likely that the horse will spend longer eating the 1 ncentrates differs considerably; as the horse will only spend approximately 10 minutes eating 1 kg of concentrates (Ellis, 2004). This means that the horse has a high energy intake in a very short time. Which, firstly, the digestive system was not evolved for and secondly, the horse will spend much less time eating and chewing. This might result in a higher risk and occurrence of undesirable stereotypic behaviour and other health problems (Davidson and Harris, 2000) and might therefore influence the short and long term performance of the horse.

The horse's teeth have evolved for heavy wearing exposure and thus would need similar conditions in order to wear at normal rates (Baker and Easley, 1951). It has been observed that the change of the angle of the incisors, commonly in domestic horses is something which does not occur to such an extent in feral or wild horses. This means that abnormal wear takes place in many of the domestic horses. Such misalignments can have severe consequences on digestion and the whole equine body. As the tempro-mandibular joint becomes further misaligned it exerts a crucial role in altering the biomechanics of the whole body. Besides that, a change in the angle of the incisors means that the surface to surface contact of the molars is also put in an abnormal state forcing the horse to clinch its jaw in order to be able to chew feedstuff properly (LaFlure, 2001). Reasons for that abnormal wear are firstly, that the horse is fed with too little high fibre roughage. Secondly, it does not need to bite correctly anymore (reduced usage of the incisors), because the roughage is most likely precut. And, thirdly, the horse gets too much concentrated energy on which it needs to chew at least four time less than on hay (approximately 3000 chewing movements on 1 kg hay and 750 on 1 kg concentrates) (Frape, 1998).

As the production of salvia is linked to chewing (Alexander and Hickson, 1970) direct relations can and must be drawn. While eating a minimum of 14 hours a day and an amount of approximately 2–2.5% Dry Matter of the body weight, the horse produces approximately 4,5 litres of saliva per one Kilogram Dry Matter roughage, resulting in approximately 40–60 liters of saliva per day (Harris, 1999; McGreevy, 2004). Producing sufficient salvia is crucial for the buffering effect of stomach acidity. Saliva, with its high bicarbonate content, has an alkaline level and thus is able to balance the acid level in the stomach (Picavet, 2002). If insufficient saliva is produced at constant rates spread over the whole day, the buffering effects of the alkaline bicarbonate are diminished; the gastric acidity rises and risk of gastric ulceration increases considerably (Pagan, 1997). It has been observed that the occurrence of gastric ulceration happens most commonly in the upper region of the horse's stomach, as this part of the stomach does not contain a mucous membrane layer and neither produces alkaline bicarbonate as an acid neutralizer. The only protection that the upper region of the stomach has from gastric acid is the bicarbonate coming from sufficient saliva production and the natural buffering capacity of roughage (Pagan, 2008). Being exposed to a higher acidic level for more than three to four hours decreases tissue resistance dramatically, and the first signs of damage become visible after ten to twelve hours (Steward, 2003). Studies show that approximately 60% of performance horses and approximately 37% of leisure horses show gastric ulceration (Picavet, 2002). The highest occurrence of gastric ulceration is found in race horses. More than 90% of all race horses show gastric ulcerations to various degrees (Pagan, 2008). It has been indicated that horses would not voluntary starve themselves for more than four hours (Krazak, et al., 1991) as acid levels in the stomach increase by then; causing discomfort and initiating the desire to chew and graze, which effectively supplies buffering alkaline bicarbonate to the affected over acidic area.

Having evolved as a constant browser grazer also means that constant movement of the digestive tract is present and necessary to keep the micro environment healthy and active. The presence of beneficial bacteria prevents the spreading of other, potentially pathogenic bacteria (Pagan, 2008). If this constant peristaltic movement is not assured, the risk of colic (abdominal pain) increases considerably. In order to guarantee this peristaltic movement, the stabled horse being restricted in roughage intake will often be observed occupying itself with eating it's bedding, because it lacks fibre, saliva production as well as it needs to occupy it's time. Eating bedding is certainly beneficial for chewing, saliva production and time occupation and thus helpful in decreasing the risk of gastric ulceration, but straw bedding should not be the major source of roughage (it has almost no nutritional value and contains larger amounts of lignin, which is more difficult to digest.) However and importantly, excessive consumption of wheat straw bedding, has been implicated in the development of impaction colic (Thorne, et al., 2005; Cohen, et al., 1999).

Applying sub-optimal feeding regimes, not guaranteeing the natural requirements of almost constant eating, chewing, producing saliva and having a "full" digestive tract, does have severe consequences on physical and mental health. The development of gastric ulceration, colic, but also the development of abnormal behaviours, such as crib biting, (e.g. Kiley-Worthington, 1987; McGreevy, et al., 1995) might result and with that have a direct influence on the horses welfare, well-being and thus on the five freedoms (Waran, 2007).

English Edit Courtesy of Tamlyn Labuschagne Ennor 2012