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Concentrate feed – friend or foe? Domestication Before horses were domesticated they fed on large amounts of forage (1). They would feed primarily on the leaves, buds and stems of plants along with a lot of grass (2). This provided a high fibre, low starch and energy diet (3), with higher amounts of starch from seed heads in the summer (4). Their digestive system has adapted alongside this diet allowing efficient hindgut fermentation of high fibre feeds (1, 5, 6). Horses would graze for about 16 to 18 hours a day (3) using a patch foraging strategy (7). However, we now feed horses on diets quite different from their natural ones. Now horses are domesticated they feed for 6-10 hours (2), some even less as many working horses simply don’t have the time to feed for such long periods. Horses are still fed forages, but along with vitamin and mineral supplements, such as salt licks to replenish salt lost in sweat (8, 9), and many horses are fed large amounts of high starch concentrates. Factors affecting diet choice There are many elements to consider when feeding your horse in order to ensure all the nutritional requirements are fulfilled. There are several factors of a horses’ lifestyle which influence its nutritional requirements and therefore the choice of diet. There are different ratios of feed that can be supplied according to how much work is done from light to fast (10). Energy needs to be provided to maintain the processes occurring within the body (11). The maintenance for a horse is to consume 2.5% of their body weight, so for a 500kg horse it should eat 12.5kg of food per day (10). Below are the rations required per day by a 500kg horse at different work levels. 

Light work - hay to concentrate ratio 80:20, with 8.5kg of hay and 2kg of concentrate . Light to medium - ratio 70:30, with 7.5kg of hay and 3.5kg of concentrate (10). Medium - ratio 60:40, with 6.5kg of hay and 5kg of concentrate (10). Hard - ratio 50:50, with 6kg of hay and 6kg of concentrate (10). Fast - ratio 50:50, with 6kg of hay and 6kg of concentrate (10).

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If a mare is pregnant or lactating it will need a lot more energy (12). Another factor is the age of a horse; older horses have altered metabolic activities which can affect diet choice (13). There are major problems with overweight and underweight horses. Owners first need to identify the problem, by using tape measurements along with body condition scoring (11), and then the diet needs to be managed and controlled to get the horse back to the correct weight. In addition, it is important to know about your horses’ genetic history and whether it has had any previous disorders (14), so that the diet and management can be tailored to help prevent them.

Concentrates Widespread use of concentrates occurred roughly 350 years ago (1), concentrates are the grains of plants, such as oats, maize or barley (1). They have a high starch content, containing 60% to 80% starch (1), which when broken down along with other nutrients provides energy, that can then be utilised by the horse for work and growth (6). Concentrate grains can be processed in many different ways, they can be crushed, rolled, micronized, popped, extruded, pelleted and many more (15). These processing methods are carried out to either increase the digestibility of starch (2) or for aesthetic reasons like flaking (11). Concentrates can also be provided as a coarse mix, horses that have reduced appetite due to strenuous work are more likely to eat these mixes (12). Problems with concentrates Did you know? • • • •

Oats – contain higher amounts of fibre than other concentrates, but have a lower energy content. It is a safer energy source especially when grinded (16, 17). Barley – has a greater energy value, and is harder than oats to digest, therefore it requires processing (16). Maize – contains high amounts of starch with higher energy content than barley and oats (16). Wheat and rye – become sticky in the stomach causing the contents to become glutinous, which may cause severe bacterial disruptions (9).

Firstly, a horses’ digestive tract is built to digest high-fibre feed (3). The digestive tract (Figure 1) is made up of two main compartments, the stomach (caecum) and the hindgut (colon), which are joined up by the relatively short small intestine (5, 12). The digestive tract wasn’t built to digest high amounts of starch, therefore concentrates have digestive and metabolic limitations (6). Especially large concentrate meals can overwhelm the digestive system, as there is Figure 1: tract of a horse What happens in the digestive system when horses areThe feddigestive high concentrate diets?(18).     

Large portions of starch can escape absorption in the small intestine which then enters the caecum (16). Fermentation occurs by bacteria and an accumulation of lactate occurs as the number of bacteria increases (15). The pH level in the hindgut decreases causing an acidic environment, which can lead to lactate acidosis, colic, laminitis and diarrhoea (2). A decrease occurs in the digestion of fibre and the production of volatile fatty acids (VFAs) which are a further source of energy (16). May also release bad endotoxins which can lead to colic (16).

limited a capacity (6), which can lead to gastric ulcers and laminitis (2). Sudden changes in the diet can also modify the bacteria present and the activities of the hindgut (14, 15). Horses fed high concentrate rations in their diets have an increased risk of digestive and metabolic disorders (1, 2, 5, 14, 16). Secondly feeding concentrates can affect the behaviour of the horse, pawing at the ground has been observed in stabled horses (7). This behaviour indicates frustration and unease and can also be a sign of colic (7). Other stereotypical behaviours are crib-biting, weaving, windsucking and coprophagy (2). Thirdly, the nutrients within concentrates are not utilised as efficiently as we think they do (19). One reason is due to the presentation of the food, for example pelleting, which can effect retention time of digesta and this therefore reduces the acquisition of nutrients (5). Excessive heat treatment when processing grains can also have a negative effect on the digestibility (16). When food is presented in flakes or pellets, this doesn’t promote chewing and reduces feeding time (5). Less saliva is produced and this can cause digestive problems like colic to occur (2). Finally, there are welfare issues associated with feeding horses’ food that leads to a high risk of disorders that cause pain and illness. Feeding concentrates doesn’t provide the horse with the physiological need of feeling full that feeding fibre provides (20). Surely we shouldn’t provide food that is likely to lead to illness, just so that we are able to exploit horses for leisure and work. Pathologies associated with concentrates Colic – abdominal pain, inflammation and/or bloating usually caused by diet. Can occur after a sudden change of stables (21), of diet or after a large amount of concentrate has been consumed (14). Continuous access to pasture can lead to colic, especially in sandy regions (14). Equine metabolic syndrome – is linked to obesity, insulin resistance and laminitis or a history of laminitis (14, 22). Usually occurs in horses from 5 to 15 years of age (14). Laminitis – is the second biggest killer of horses after colic (20). Where the epidermal lamellae of the inner hoof wall separates from the dermal lamellae of the distal phalanx (meaning the bottommost bone in the horse) resulting in lameness (23). Gastric ulceration – can occur in performance horses, it has been shown that 80-90% of racehorses in training had gastric ulcers (4). Factors that contribute to the disorder are confinement to stalls, strenuous exercise and high grain ratios (4). What can be done to prevent the problems of feeding concentrates?   

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Should feed lower amounts of concentrates and when possible none at all. A grainbased meal should not exceed 0.2-0.4% BW per meal (4). Concentrate rations should be divided amongst several meals throughout the day (12) . Feeding forage 15 minutes before concentrate can stimulate saliva production allowing better rate of passage through the digestive system (19), can also mix concentrates with small amounts of forage to aid digestion (9). Try feeding multiple types of concentrate diets to reflect patch foraging strategies, and to increase foraging periods, making it more natural for them (7). Feed higher quality forages to preserve digestive abilities (15). If a change in diet is needed phase it in gradually rather than an abrupt introduction

Friend or foe? Concentrate feed is mainly a foe, because in large amounts there is a severe increase in the risk of many equine diseases. High amounts of starch in concentrates is unnatural and a horses’ digestive tract is simply not built to digest this type of food. High concentrate feed also effects horse behaviour, acquisition of nutrients and even makes us question horse welfare. However, it can be a friend in very small amounts for working horses, because it ensures that the horse gets the energy required, but in excess it can cause them more harm than good.

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