Dr. rer. nat. Christina Fritz, info@sanoanimal.de
Abstract
Horse feeding has undergone some major changes over the last few centuries, and particularly in the last few decades. The first major innovation came in the course of the 19th and early 20th centuries. Agriculture changed to crop rotation and to the increased cultivation of potatoes and beets instead of grain. The second factor at this time was industrialization and thus urbanization, especially in Europe. Horses were no longer kept exclusively in rural areas, but increasingly in the newly emerging and growing cities. This posed the problem of how to care for these horses, as hay and grain had to be transported from the countryside into the city and horse manure from the city back to the fields outside the cities. At the same time, the food processing industries started to generate large amounts of organic waste. Thus, the traditional feed plan for working horses was expanded from hay, straw, leaves, oats and legumes to include potatoes and beets as well as residues from grain mills, fruit-, oilseed- and sugar beet processing, and from breweries and distilleries such as pomace, bran, residual flour, spent grain, stillage, yeast, malt, etc..
After the end of the Second World War and the resulting collapse of the horse population in Europe – not least due to the advent of the automobile as a means of transport – the feeding of horses returned to the original habits: hay, pasture, oats and mineral feed, as they disappeared from the cities and were mostly kept out of tradition in rural areas. Only when horse riding emerged as a popular sport in the 1980s and more and more people fulfilled their dream of owning a horse, their numbers started growing again. From the 1990s onwards, horse owners were also discovered as wealthy customers by the feed industry, which until then had mainly supplied the extremely price-sensitive fattening and dairy industries.
Consequently, over the past 30 years, a completely new feed industry has emerged around this growing number of “luxury horses”. Since there is no sensible reason for horse owners to buy mixed feed for a price significantly higher than a bag of oats, this industry had to first create its own market and profit margin. To do this, they took a trip back to the era of industrialization, combined it with the know-how of livestock feed production, and started converting cheap waste products from the food industry into profitable horse feed brands. These waste products are “refined” for the horse’s taste with molasses, pomace and thermal treatment of poorly digestible cheap grains like corn. Essential oils are added for the owner’s nose as well chaff that creates the illusion of “naturalness”. This the delicious “horse muesli” comes in colorful, attractive packaging to convince the owner of the high product value.
Today, horse owners can choose from a confusingly broad selection of mixed feeds for sport and leisure horses, for western and pony breeds, for healthy and metabolically sick horses. The ingredients of these various feeds usually differ only slightly. The result of this “food waste disposal via the horse’s stomach” is a rapid increase in horses with metabolic diseases, from laminitis to sweet itch, from EMS to Cushing’s disease, whose treatment by veterinarians must remain unsuccessful until the horses’ feeding is changed back to a species-appropriate diet. The fasciae – being part of the connective tissue – hereby serve as an intermediate waste storage system for feed ingredients that can neither be used, nor excreted in sufficient amounts to balance the system. The resulting gait abnormalities we so often see in our patients, that are usually accompanied by high LDH and CK values in the bloodworks, will only respond to manual therapy methods, when the feeding is turned back to a natural diet and the detoxification system is re-balanced.
Introduction
With the domestication of the wild horse around 5,000 – 6,000 years ago, the horse’s diet did not change much at first. The first horses kept by nomadic peoples in the Kazakh steppe essentially ate what grew in their environment, i.e. the same food that their wild relatives ate. Even when people in northern and western Europe began to domesticate horses, they continued to feed them like their feral relatives. These horses – like horses in most non-industrialized parts of the world today – had to work hard: carry loads, pull carts and serve as riding horses. At the same time, the diet was largely limited to what grew locally and was cheap to obtain: whole plants growing in meadows and fields. Thus the ideal diet for the herbivorous horse.
This changed mainly in the course of the 19th and early 20th centuries. Industrialization caused cities in Europe to grow, and with it not only their two-legged but also their four-legged population. While dogs – which had long been parasites at people’s tables – were still able to thrive quite well on the food waste of the population and leftovers from abattoirs, supplying horses with adequate feed was a major problem. It was hardly possible to transport sufficient quantities of hay of the appropriate quality to the cities and store it there. In addition to traditional feedstuffs such as meadow grass, hay, straw, legumes, leaves and oats, more and more waste products were added that accrued in the cities’ food factories. These included residues from grain, oilseed and sugar beet processing, from breweries and distilleries, as well as products of animal origin. Potato peels, sugar beet pulp, apple pomace, wheat bran, residual flour, spent grain, stillage, yeast, malt and many other waste materials were processed into horse feed. People began to experiment with different feed preparations and additives to make feeding easier and cheaper, while maintaining the same level of horse performance – after all, the horses were still doing hard work every day.
The biggest problem posed the horses’ tricky feeding habits. This had already been discovered by the military, which from around 1800 onwards carried out experiments with biscuits, rusks, cakes and similar forms in order to produce large quantities of cheap, long-lasting and easily transportable feed for its cavalry. Unfortunately, the energy-rich and inexpensive industrial waste was often completely unappealing to the horse in terms of smell and taste. The use of molasses as a “flavor additive” around 1890 finally was the key. This led to horse feed produced from food industry waste becoming a gamechanger for working and military horses. Around 1900 there were around 4.2 million horses in Germany alone that needed to be fed, the majority of them in the rapidly growing cities. Thus, between 1800 and 1945, a variety of “new” horse feeds were developed to replace a large part of the hay ration with ingredients that were inexpensive as well as easy to transport and store.
However, the horse world in Europe changed significantly after the end of the Second World War. The automobile replaced the horse as a cart or carriage pulling and pack animal, so the horse numbers dropped. They were only kept in the countryside out of sentiment, but not used as workforce anymore. Until in the 1980s their star began to rise again, this time as a leisure and sports partner. As prosperity increased, more and more people were able to keep a horse – not as a work animal, but as an activity for their new-found free time: horseback riding as a hobby was invented. According to a survey by the Institute for Public Opinion Research in Allensbach, there were 3.7 million riders in Germany in 2012. According to the animal disease control funds, 840,000 horses were registered in Germany in 2011, but since not all horses are registered, it is assumed that we are talking about a total of around 1.2 million horses and ponies in Germany in 2011. According to the German Animal Nutrition Association, 267,000 tons of mixed horse feed were sold in the statistical year July 2012 – June 2013, excluding pure grains such as oats or barley. Horses and horse feed have therefore become an increasingly important economic factor for feed manufacturers. In addition, the price pressure on livestock feed is significantly higher than on horse feed, which makes this market even more attractive for manufacturers.
While every cent of costs is haggled over for pigs or cattle, horse owners are prepared to spend significant amounts on their darling. In Germany, a total of around 10 billion euros were sold in the livestock feed sector in 2022, of which around 2 billion euros came from mixed feed for horses alone. (www.statista.com, accessed 12/2023). This makes Germany, together with England, one of the most important markets for the horse feed industry. However, in addition to attractive markets such as Austria, Switzerland and the Netherlands, even countries such as Spain are now catching up since they have been intensively targeted by the sales departments of the feed industry. This factor is not least ensuring that more and more feed manufacturers are serving the horse sector in addition to the livestock sector.
The profit margins on horse mixed feed are considerable. While horse owners pay between 8 and 12 euros for a 25kg bag of oats or barley, a bag of mixed feed can easily cost 15 – 30 euros. Not only is the price more expensive, but the bags are usually smaller, around 15 – 20kg. The owner is made to believe that only the best ingredients definitely justify the higher price, because that is what the marketing suggests. Unfortunately, this is far from true. The production costs of a bag of horse mixed feed are normally between 1 and 5 euros. In order to achieve these production costs, the use of “by-products” – as food waste is euphemistically described – and “low-energy fillers” is now the standard in the horse feed industry.
There is actually no good reason to give horses mixed feed instead of hay and maybe a bit of oats or barley for sporthorses. Large investments in marketing and sales were necessary to create a horse mixed feed market, first. The Hoeveler company started the “modern” horse feed success story with its “Reform Oats”. Horses liked these oats mixed with sweet molasses (waste from sugar production) much better than non-molassed oats – what a surprise. The company built on this success and introduced molasses as an almost indispensable “flavor” in horse feed. And if the horse eats its feed enthusiastically, the owner is happy. The fact that the majority of horse owners in western Europe are women who just love to “feed their babies” opens the door wide to manipulating horse feed in such a way that it pleases both horse and rider.
Therefore, the feed is not only designed to be tasty for the horse by adding sugar (molasses) and / or fat (plant oils or leftovers from plant oil production). It is also visually refined to suit the potential buyer. While the competition rider expects mainly grain in his horse feed, the leisure rider wants to see chaff-enriched feed that gives the impression of naturalness – even if it is only finely chopped hay or alfalfa stalks, so basically a very expensive way of feeding forage. The high number of overweight and metabolically sick horses, as a result of these mixed feeds, has led to the development of “grain-free mueslis”, and many “special feeds” that are now available to the horse owner. They are supposed to help against metabolic diseases from PSSM to laminitis, from EMS to topline syndrome. Some of the feeds do even lead to a short-term improvement in symptoms, but in most cases new and often worse symptoms appear elsewhere in the body after a time delay as a result of these feeds.
Mixed horse feeds made from food waste products do not provide species-appropriate nutrition; instead, they serve to fill the pockets of horse feed manufacturers. Consequently, the feed industry remains enthusiastic, producing seemingly suitable mixed feeds for every horse and rider. These feeds often include flavourings such as peppermint or eucalyptus oil to enhance their appearance and give them a “natural” appearance.
Waste products used most frequently in horse feed
Waste from the grain processing industry
When processing grain in the mills, after the husks have been peeled and then milled, various fractions are created that are used for different purposes. The flour yield from the whole grain is on average around 80%, so around 20% of waste materials are generated in this process. Around half of this is bran. The remaining 10% is divided into around 6% semolina bran and around 4% secondary or feed flour.
Husks
Some grains, such as spelt, have to be separated from their husks (“hulled”) before the grain can be further processed. This means that substantial quantities of spelt husks are generated in the mills, as the husks make up around 30-40% of the harvest of those grain types. The husks cannot be reused in the food industry. Some of the spelt husks are used as bedding for laying hens or (pelleted) for livestock. Spelt husks are also used in biogas plants or as pillow filling for people with allergies. In addition, spelt husks are increasingly used in mixed feed for horses, especially in “grain-free” muesli for leisure horses. This is because spelt husks provide a large volume with low nutritional value and at extremely low cost. In terms of its composition, spelt husks can be considered like straw, i.e. they contain a large amount of lignin, making them practically indigestible for horses. However, due to their length, they cannot be chewed sufficiently – in comparison to straw – and therefore reach the digestive tract almost unchanged. Since spelt husks have a strong abrasive effect, feeding them can lead to inflammation of the mucous membranes in the digestive tract. In addition, their length often causes dysbiosis in the large intestine, as they can cause a counter-rotating peristaltic wave in the ventral colon. Overall, spelt husks are worthless from a nutritional point of view and a potentially problematic feed and should therefore be avoided in mixed feed.
Wheat bran
Wheat bran is a “big business” with a global market volume of around 20 billion US dollars, of which around 90% ends up in animal feed. On average, wheat bran contains around 10-20% wheat starch. As long as it is fed in moderate amounts and only for a limited time, this proportion does not pose a problem for a healthy digestive system. However, added to mixed feeds that are fed all year round, this starch content can cause inflammation of the intestinal mucosa in horses to become chronic. Wheat bran is also problematic in terms of mineral balance. On the one hand, it contains a high level of phosphorus (approx. 11.53g/kg) in relation to calcium (approx. 1.58g/kg). On the other hand, it also has a high content of phytic acid (phytate). This phytate can impair the absorption of minerals such as calcium (and to a certain extent zinc, phosphorus and magnesium) in the horse’s intestines, as it forms insoluble chelates with these minerals. In particular, the binding of calcium by phytate can contribute to the formation of stomach stones as well as to an unfavorable calcium-phosphorus balance and can have a negative impact on bone health in the long term. This effect is particularly relevant for horses. The “Krüsch disease” that was previously common in horses, also known as “Big Head”, “Baker’s or Miller’s Horse Disease”, was most likely the result of an unbalanced calcium-phosphorus ratio, which can be caused by the high phytate content when feeding generous amounts of wheat bran. This disease can lead to bone deformations and growths as well as other health problems.
Oat bran
This is the residue left over from the oats’ husks and shells when oats are processed into fine oat flakes or oat flour. Oat bran for horse feed usually includes the husk (except when processing naked oats, which is why the nutritional information sometimes varies greatly), plus the seed coat including the aleurone layer and the grain outer layers, as well as the germ. In particular, as a result of the increasing use of oat products as milk substitutes, more and more oat bran is being produced, which is mainly processed into animal feed. In terms of nutrient content, oat bran is not comparable to wheat bran. The crude fiber content is 20-30%, with the crude fiber content varying greatly depending on the husk content. The starch content is usually 10-16%. Oat bran is used in livestock feed primarily as a source of fiber and in mixed feed for horses as a cheap filler with comparatively low nutritional value. In addition, oat bran contains on average around 8% beta-glucan, which is considered a soluble fiber. It swells up strongly to form a gel and can form a protective film over the stomach and intestinal mucous membranes, so that horses with inflammatory processes in the stomach and small intestine in particular can benefit from feeding it. However, it must be ensured that the product used still contains beta-glucans, as oat bran is also used for the production of beta-glucan and the waste products resulting from this process are sometimes sold (pelletized) as oat bran, too. It is also important to pay attention to the residual starch content, as starch has a negative effect on stomach ulcers.
Rice bran
The by-product of rice processing known as rice bran consists of husk parts and the aleurone layer that lies between the endosperm and the husk of the rice grain. The rice bran also contains the germ and the endosperm of the seed and makes up a total of around 8% of the weight. Around 76 million tons of rice bran are produced worldwide every year as a waste product from the food industry. Rice bran contains, similar to whole rice, around 0.45% γ-oryzanol. In addition to phytosterols, it is particularly rich in fat (around 18%) and protein (around 15%) with an amino acid profile roughly between that of oats and legumes. In addition, rice bran always contains a relatively high proportion of starch due to the process, on average around 30%, with a low proportion of crude fiber (8-9%). In particular, the marketing of rice bran as “grain-free” horse feed, which is suitable for horses with PSSM, EMS or a tendency to laminitis, which should be fed a low-sugar, starch-free diet, is to be viewed more than critically in view of the high starch content of 30%. By comparison: whole oats contain around 40% starch. The raw materials used for horse feed usually contain stabilized rice bran (usually heat-treated at 135°C) as well as added antioxidants as preservatives and calcium to improve the calcium-phosphorus ratio. The heat treatment increases the risk of allergies, which should be taken into account especially in horses with inflammatory processes in the digestive tract.
Semolina bran and feed flour
These waste products are mainly used in animal feed, as they are practically unsuitable for human consumption. While the bran is largely free of endosperm and should only contain a small amount of starch, this does not apply to the other products from this process. Therefore, semolina bran should not be equated with bran. Semolina bran usually has a starch content of <20%, as it still contains a proportion of shell residues that must be declared as crude fiber. Wheat in particular is often declared several times in the same horse feed, for example as wheat, wheat flakes, wheat semolina bran and wheat meal/feed flour. In total, this sometimes results in significant levels of wheat with all of its negative consequences for the horse’s digestive tract, as wheat has been proven to cause inflammation of the gastrointestinal mucosa in horses.
Gluten protein
Sometimes you will find “gluten protein” declared in horse feed. This is the separated gluten protein that remains as waste during starch production. In most cases, corn gluten is used in horse feed. This is left over from corn starch production for food and bioplastic production and has a crude protein content of around 60%. Corn protein is of extremely poor quality for horses. So the addition of corn gluten to mixed feed does increase the crude protein content, but unfortunately its unfavorable amino acid pattern does not improve muscle building, but merely puts a strain on the kidneys because more urea has to be excreted. “Corn gluten feed” is a mixture of several waste products. For this purpose, corn gluten, corn germ extraction meal (waste from corn germ oil production) and shell residues are mixed and used as animal feed. The crude protein content is thus reduced to about 20-36% compared to pure corn gluten, while the starch content increases to about 20%.
Waste from breweries
Breweries produce a large amount of waste from the brewing process, which ultimately ends up in horse feed. The most commonly used materials are spent grain and brewer’s yeast (Saccharomyces cerevisiae), which make up by far the largest part of brewery waste, as brewer’s yeast accounts for around 3% of the brewing volume. They are usually traded for less than 1 euro cent per kg (= 0.01 euros/kg), making them an extremely cheap raw material for producing “high-quality” horse feed. With an average sales price of 7 Euros per kg (3.20-18.76 euros per kg www.pferdefuttershop.de, as of 06/2024) for pure brewer’s yeast or BT yeast, the manufacturer already has a decent profit margin. Some of the yeast is used by the food industry to produce yeast extracts, which ultimately end up on supermarket shelves, especially in ready-made soups and soup seasonings. The difficult-to-digest spent grain is sometimes used as a substrate for mushroom cultivation. There are also ongoing studies into its industrial use, although none of these are currently of commercial interest. Therefore, spent grain is also used more frequently in horse feed, usually mixed with brewer’s yeast and then labelled as brewer’s yeast/spent grain or BT yeast.
Spent grain
This is the remains of hops, malt and barley or wheat that could not be broken down by the brewer’s yeast in the brewing process. Spent grain itself is considered difficult to digest and is mainly used as a cheap source of protein for livestock due to its crude protein content of around 25-28% on average. It also provides crude fat in the range of 7-12%, around 15-18% crude fiber and around 4-5% crude ash, which is characterized above all by high phosphorus content. Brewer’s grain is largely free of starch and sugar, as these were converted to ethanol in the brewing process. Starch is usually only found in values of 3-5%. In order to increase digestibility, especially for cattle, spent grain is sometimes ensiled before being fed. Brewer’s grain has not played a role as horse feed to date, it is only contained in many brewer’s yeast products, since the process of separating spent grain from yeast cells makes pure brewers yeast a bit more expensive.
Brewer’s yeast / baker’s yeast (Saccharomyces cerevisiae)
Brewer’s yeast is often praised as a feed for horses due to its nutritional value. Depending on which yeast strains were used for the brewing process, the crude protein value is 40-75%, the crude fat content is 0.2-3.5%, crude ash in the range of 6-14% and carbohydrates are 13-27%, although these are mainly present as beta-glucans and other polysaccharides, but not as starch. The high content of B vitamins is also often highlighted, with nicotinic acid (B3) being by far the most detectable in most studies at up to 72 mg/100 g. This is followed by significantly lower amounts of pyridoxine (B6) at 6-55 mg/100 g, folic acid (B9) at 0.25-5.3 mg/kg, riboflavin (B2) at 0-10 mg/kg and thiamine (B1) at 0-7.5 mg/kg, with the important cyanocobalamin (B12) coming in a last place at 0-0.16 mg/kg, as it is not detectable at all in many yeast strains. All B vitamins, especially vitamin B12 and active vitamin B6 (pyridoxal-5-phosphate), are provided in horses by a healthy colon microbiome in more than sufficient quantities and do not have to be included in the feed.
The study situation on feeding brewer’s yeast is very inconsistent overall. There are significantly more studies on its use in livestock than in horses. In livestock, brewer’s yeast is used in particular to accelerate weight gain during fattening. This effect is particularly clear in comparison to control groups when the animals are kept under stress and under severe disease pressure. The mechanism why brewer’s yeast leads to a more significant weight gain in stressed animals than in non-stressed animals is not yet known. In pigs, it has been proven that although the addition of brewer’s yeast leads to faster weight gain, the diversity of the microbiome in the intestine decreases significantly at the same time. The fattening-accelerating effect has nothing to do with a healthier microbiome through the feeding of brewer’s yeast.
Even in rabbits, whose digestive system is the most similar to that of horses of all farm animals, the addition of brewer’s yeast to the diet leads to a significantly higher weight gain and an increase in blood parameters that indicate chronic inflammation when otherwise fed the same. Obesity is now a widespread problem in our domesticated horses, and there are certainly many causes for it. But in this context, it is questionable to what extent feeding horses a feed that accelerates fattening, such as brewer’s yeast, really makes sense. Many manufacturers point out that studies on horses have shown that feeding brewer’s yeast increases fiber digestibility (in fact, this is just one single study). What is not mentioned here is the fact that in this study, a high level of starch in the form of grains (barley) – that are difficult to digest so a lot of the starch ends up in the hindgut – was also fed. The experimental setup here was basically with three groups of horses:
• barley+brewer’s yeast+hay
• barley+hay (control)
• Hay (control)
In this study design, improvements were observed in the horses that were fed barley+brewer’s yeast+hay compared to the barley+hay group, so a high-carbohydrate diet but without brewer’s yeast. Unfortunately, the result of the barley+brewer’s yeast+hay group did not differ at all from the control group, which was only fed hay, without brewer’s yeast and without starch. This of course creates a completely distorted picture if you only take the statement that brewer’s yeast “promotes fiber digestibility” – but only if fiber digestion is otherwise disturbed by high amounts of starch. So you only reach the level that horses have anyway when fed hay alone if you leave out the starch that causes dysbiosis. Why the difference? The only explanation for the results of this study is that the brewers yeast digested the starch during small intestine passage, before it could reach the hindgut. When brewer’s yeast digests starch, it produces alcohol, something you probably don’t want to happen in the horses digestive system.
A similar experiment was carried out on rabbits, except that there were four groups:
• grain+brewer’s yeast+hay
• grain+hay (control 1)
• Brewer’s yeast+hay (control 2)
• Hay (control 3)
There was no difference in fiber digestion between the brewer’s yeast+hay group and the hay group. Only better fiber digestion was observed in the grain+brewer’s yeast+hay group compared to the grain+hay group, i.e. the same picture as in horses. It can therefore be assumed that brewer’s yeast has no positive influence on fiber digestibility in the large intestine in a horse fed a species-appropriate diet.
Brewer’s yeast has the ability to convert low-molecular carbohydrates such as glucose into alcohol and CO2, which is why it is used in the brewing process and in wine production. It is responsible for the alcohol in beer (or wine) and for the formation of bubbles (CO2) when making yeast dough for bread. The more sugar or starch there is, the more alcohol and CO2 is produced. For this activity, zinc is needed as a substrate, which is then removed from the environment. In view of the zinc deficiency that is now widespread in horses, one has to ask to what extent this has to do with the increase in brewer’s yeast in horse feed.
The so-called auto-brewery syndrome has been known in humans for a long time. It can be triggered by various yeasts from the Candida and Saccharomyces families and causes the affected patients to metabolize carbohydrates into alcohol when the yeast settles in the digestive tract. These patients have increased blood alcohol levels simply from carbohydrate intake, without having directly consumed alcohol. If these patients also have diabetes, obesity or liver disease, their blood alcohol levels rise even further. Stress and long breaks between meals can also lead to a significant increase in blood alcohol levels in affected people. Possible causes that can contribute to the development of this syndrome include frequent or long-term antibiotic use, a carbohydrate-rich diet, diabetes and a possibly genetically determined reduction in liver enzyme activity.
Chronic inflammation of the intestinal mucosa, such as that associated with Crohn’s disease, can also be related to auto-brewery syndrome, but it also occurs in patients without any accompanying or previous illnesses. In humans, auto-brewery syndrome leads to a deficiency in B vitamins, zinc and magnesium. While brewer’s yeast is advertised as a source of B vitamins, it can in fact have the exact opposite effect if it settles in the intestine. To date, there have been no studies on auto-brewery syndrome in horses or other animal species. In human medicine, it is assumed that significantly more people suffer from auto-brewery syndrome than are diagnosed, as this condition is often unknown to general practitioners. If you now take into account that yeast can easily survive the passage through the horse’s stomach and that the horse’s large intestine is nothing more than a large fermenter for microorganisms, then it is easy to imagine that feeding brewer’s yeast can also lead to auto-brewery syndrome. To no surprise, a lot of horses that received brewer’s yeast in the past suffer from bloating (“pregnant gelding syndrome”).
Finally, it should be mentioned that numerous publications have already reported that brewer’s yeast is contaminated with antibiotics and mycotoxins as a result of the manufacturing process. These also have far-reaching, negative effects on the microbiome of the horse’s intestine. The conclusion is: brewer’s yeast has no proven benefit for the horse’s digestion and metabolism, but can cause damage under certain circumstances by triggering dysbiosis in the large intestine and disturbing the vitamin and trace element metabolism. It should therefore not be fed to horses.
Waste from the fruit and vegetable processing industry
Fruits and vegetables produce basically two kinds of waste products that are used in horse feed: pomace as a leftover of juice production consists basically of pectin as the dominating plant fiber, as well as sugar, acids and only few nutrients, since they were extracted with the juice. Additionally feed manufacturers use peels from the processing of fruits and vegetables for convenience food, which consist of pectin, plus slightly more nutrients, on the cost of a higher risk of contamination with pesticides or preservatives that often cover the peels.
Apple pomace
Pomace is the residue from juice production, so apple pomace is created during the processing of apples (sometimes mixed with pears) into juice or wine (cider). The apples are first crushed and then pressed to extract the juice. The remaining solid matter, consisting of peels, cores and pulp residues, is called apple pomace. In Germany alone, around 300,000 tons (2021) of apple pomace are produced annually, with the amount fluctuating greatly depending on the apple harvest and the demand for apple juice. This pomace is low in protein (crude protein around 5%), but rich in plant fibers (crude fiber content around 20-22%), with around half of this being pectins, which can contribute to acidifying the intestinal tract in horses. In addition, they contain around 2-3% crude ash and 4-7% fat. The residual sugar content can be between 10 and 40%, depending on the variety. Alcoholic fermentation begins about half an hour after production. The dried product is therefore usually enriched with yeast, which passes into its persistence stage during the drying process (spore formation). Apple pomace is very often found in horse feed, both as pellets and mixed in loosely. In mixed feeds, it serves as a cheap, fiber-rich filler and its taste also ensures that the feed is better accepted by horses, since it adds to a sweet taste. In mineral feeds, apple pomace is more often used as a carrier, whereby its relatively high sugar content is often able to “mask” less tasty (organic) mineral compounds, so that the horses will better accept the feed. In terms of nutritional value, apple pomace is largely worthless. However, due to its high pectin and sugar content, it should be avoided in horse feed, since pectins contribute to hindgut acidification, followed by dysbiosis and colitis.
Citrus pomace
Similar to apple pomace, citrus fruit processing also produces waste in the form of pomace. The citrus fruits, which include oranges, lemons, limes and grapefruits, are first pressed to extract the juice. The remaining solid matter, which contains peel, pulp residues and seeds, is called citrus pomace. Citrus pomace is advertised in particular for its high fiber content, which essentially consists of hemicelluloses, cellulose and pectins. The crude fiber content is stated as 10-50%. These strong fluctuations are probably due to the fact that citrus pomace is partly used first for pectin production and the resulting pressing residues are also marketed as citrus pomace. So you don’t know what the fiber composition of the final product really looks like, especially since citrus pomace is usually added to the mixed feed as one of many components in the horse feed sector, which leads to a shift in the analysis data due to the other components. The crude protein content of citrus pomace is only around 6.5%, crude fat around 4% and crude ash 0.5%, so citrus pomace is also an inferior feed. Lime is used to neutralize the fruit acids before it is sold as feed, which led to a dioxin scandal in citrus pomace in 1999 because the lime used was contaminated. The neutralized pomace is then pressed into pellets, to which molasses, fat or colloidal clays (e.g. bentonite) are often added as a binding agent, which further changes the taste and increases acceptance by the animals. The EU imports around 2 million tons of citrus pomace annually (2022), mainly from Brazil and the USA.
Citrus pomace contains about 22% sugar and otherwise consists mainly of plant fibers, the exact composition of which is usually not declared. Due to the possibly high pectin content, citrus pomace is very often used in feed recommended for horses with stomach ulcers with the argument that the pectins form a jelly when in contact with liquid, which then forms a protective layer over the stomach walls. However, the high sugar content, which is problematic for horses with stomach ulcers, is ignored, as is the fact that a high content of pectins can lead to acidification and dysbiosis in the hindgut. Also little known is the fact that grapefruit seeds have a strong antimicrobial effect, which – if grapefruits were used to produce the citrus pomace – can also have negative effects on the hindgut microbiome. The last important point to mention is the heavy use of pesticides on citrus fruits, which have a strong antimicrobial effect to protect the fruit from rotting in the tropics. From this point of view, citrus pulp is a highly questionable feed and should therefore be avoided in horse feed.
Waste from oil production
The industrial processing of oilseeds produces various “by-products” or waste products, which are almost entirely reused in animal feed. These by-products differ in their composition and further use in detail, depending on whether they are obtained from fruits such as olives, sunflowers, rapeseed, palm trees or soybeans. After harvesting, the oilseeds are first cleaned to remove coarse impurities such as stones, stems, leaves, etc. Many oilseeds must also be peeled before pressing. These include pumpkin seeds and some sunflower seeds, which have a hard shell with a high lignin content, which would interfere with the process and absorb some of the oil. With these oilseeds, the shells –also called husks or hulls – are the first waste that is produced in the process. The shells are sometimes pressed into pellets and offered as bedding, or they are used as cheap filler in mixed feed for horses that are overweight or at risk of laminitis, for example soybean hulls or sunflower seed husks.
The peeled oilseeds or those that do not need to be peeled due to their structure (such as linseed) then go through the first, purely mechanical pressing at low temperatures. This produces the highest quality oil, which will then be filtered and later marketed as food-grade for accordingly high prices. The main by-product here is the so-called press cake, which remains after the first, mechanical cold temperature pressing of the oilseeds. The press cake has a lower crude fat content than the original oilseed but is otherwise very similar to it in composition. It is offered directly as horse feed, for example as pellet-formed hemp treats (with a high crude fat and protein contents, so they taste delicious for the horse) or linseed cake. In some cases, for example linseed, preservatives must be added to protect exposed fatty acids from oxidation. Otherwise, the press cake would go rancid and become toxic for horses.
The residual oils contained in the press cake can also be washed out in the next step with the help of solvents (usually hexane or xylene) or by adding cheaper food-grade oils. The second pressing takes place, that can be performed under cold temperatures as well. The resulting oil from this second (“wash-out”) pressing can later also be marketed as “oil from cold pressing”. Alternatively, instead of the solvent, a second pressing of the press cake can take place under heat, which releases further oils. The approach chosen depends, among other things, on the type of oil and its subsequent marketing. Linseed oil, for example, is very thermolabile and is more likely to be obtained using solvents and cold pressing. Sunflower oil, on the other hand, is very thermostable and is often pressed at temperatures of 80° to 120°C.
The end product of the washing process usually contains, in addition to the washed-out oils, other residual substances that must be separated. This process is known as refining. This includes separating the solvent, degumming (e.g. linseed, chia seeds) or neutralizing by partial saponification and washing. Undesirable color pigments can be removed with the help of activated carbon or diatomaceous earth, and the oil can also be filtered and centrifuged to eliminate unwanted waxes, such as those that can occur in olive oil, for example. Finally, it is preserved against oxidation. The oil refined in this way is then bottled and sold as a cheap cooking oil in the food sector or in large containers as feed additive for horses (e.g. linseed oil). Due to the manufacturing process, this oil is of significantly lower quality than that from the first cold pressing. As a customer, you can often only distinguish the quality of the oil by the price. High-quality oils are naturally not used in horse feeds.
After the second pressing, the extraction meal remains as a solid phase. It still contains residual oils, so it is not completely defatted. Depending on the original composition, other components may have been washed out as well, such as amino acids or the mucilage in linseed. The composition of extraction meal therefore differs significantly from the original product. Extraction meal from linseed, sunflower or soy oil production is often added to mixed feed for horses as a cheap source of protein and fat that increases the energy value of the feed without this energy actually being useful for the horse.
As palm oil and soy are increasingly being criticized by the public due to their not particularly environmentally friendly cultivation conditions, the production of coconut oil as an alternative is currently experiencing a boom. The consumer imagines a dozen coconut palms growing romantically wild on a tropical beach and being harvested by hand by well-paid locals. However, the reality is that coconut palms are planted in huge monoculture plantations in the coastal areas of tropical countries that are run in a quasi-industrial manner. Coconut palms require loose, permeable soil and tolerate relatively high levels of salt in their water. This makes them ideal for cultivation on the coast, as the tropical clay soils inland are usually not permeable enough to produce a good yield and not much else will grow along the coastlines.
The flesh of coconuts (also known as copra when dried) has a particularly high crude fat content of over 60%, with coconut oil having a low melting point (23°C). For this reason, the terms coconut fat and coconut oil are also used synonymously. Coconut fat consists mainly of saturated fatty acids (>90% of the fatty acids contained), which means it is not very sensitive to oxidation and is highly heat-stable. It is therefore particularly suitable for industrial purposes (e.g. for shampoos, cleaning agents) or is used in the food sector, for example for margarine production and for frying fats. Coconut fat has been experiencing a boom in the food sector as a “healthy fat” for some time, although this cannot be explained by the fatty acid composition of coconut fat. Nevertheless, the increased global consumption of coconut fat (around 2 billion tons annually) has now led to the production of coconut extraction meal on a large scale, which is also marketed as “de-oiled copra”.
The de-oiled coconut pulp (coconut extraction meal, copra) usually used in animal feed contains on average 2-3% crude fat, 20-25% crude protein (with an amino acid pattern that is not particularly favorable for horses), 12-16% crude fiber and 6-8% crude ash (mainly potassium) as well as around 10% sugar, which makes it very attractive to horses in terms of taste. Overall, the use of de-oiled copra in horse feed is not much less questionable for ecological reasons than the use of soy or palm oil products, since here too it is transported halfway around the world and the growing conditions are largely no more environmentally friendly than those of oil palms.
In terms of nutritional value, copra is not relevant for horse feeding, but it does meet the need of marketing departments for unique selling points. In addition, coconut meat is often advertised as having an anthelmintic effect on horses. A 2014 study on horses fed a mixture of micronized copra and onions was able to demonstrate an effect against intestinal parasites that had previously been shown in sheep with the same mixture. However, further scientific evidence is lacking on the effectiveness of coconut meat or de-oiled copra against intestinal worms in horses, especially since the study did not include control groups that received only copra or only onions (which in large amounts are toxic for horses). Overall, condensed tannins, such as those contained in sainfoin, appear to have a significantly stronger anthelmintic effect than copra. In addition, because it is grown locally, sainfoin leaves a much smaller ecological footprint than coconut products.
Waste from the sugar industry
With its sugar content of around 20%, the sugar beet has become an important source of sugar in Europe. Processing sugar beet into sugar is a complex process that involves several mechanical and chemical steps, with the main waste being beet pulp and molasses.
Beet pulp (unmolassed)
Beet pulp is the waste that remains after sugar-juice extraction. It is essentially the fiber fraction of the sugar beet, which consists largely of pectins. The pectin content in the beet pulp after juice extraction is usually around 25% of the dry matter. It is dried and processed further for animal feed. There are two types of beet pulp for horses in the feed trade: “classic” beet pulp (also known as sugar beet pulp or molasses pulp, to which molasses has been added) and “unmolassed” beet pulp (e.g. SpeediBeet® or KwikBeet®). Beet pulp is marketed loose or in pellet form as animal feed.
As sugar is increasingly being criticized when it comes to feeding horses, the feed industry has reacted and now usually offers “unmolassed” beet pulp under various trade names as horse feed. This is simply the leached beet pulp that is dried after juice extraction, pelleted if necessary and bagged directly without molasses being added beforehand. It usually has a residual sugar content of 5-8% and otherwise mainly brings pectins into the digestive tract. The other nutrients in beet pulp can largely be ignored: crude protein and crude fat contents are usually less than 1% and the leaching process washes out most of the minerals and vitamins. Adding molasses to the beet pulp increases its energy content because a high amount of sugar is added. Accordingly, the sugar content of “normal” beet pulp is on average 15-25%. It is well known that high sugar contents are problematic with regard to obesity (EMS, pseudo-EMS) and insulin dysregulation.
Beet pulp is sometimes also advertised as a forage substitute when hay prices are very high or the hay quality is poor or there is a generally low supply of hay, as is often the case in arid regions. In these cases, the beet pulp is sometimes fed in quantities of up to 20kg/day, as it practically completely replaces the hay ration. Unfortunately, this “forage substitute” consists mainly of pectins, rather than healthy cellulose, the natural microbiome depends upon. The high pectin content in unmolassed beet pulp leads to acidification of the large intestine and consequently dysbiosis, since pectins are largely digested by protozoa that produce a wide array of acids as a result that can not be sufficiently neutralized during the colon passage. Therefore, the recommendation to feed unmolassed beet pulp to horses with a predisposition to laminitis is particularly problematic because many acute episodes of laminitis result from acidification of the large intestine (endotoxin-related laminitis, fructane-triggered laminitis). The aggressively marketed recommendation to feed unmolassed beet pulp is one of the reasons why so many horses fed beet pulp have severe lymphatic and metabolic disorders like Pseudo-EMS, Kryptopyrroluria (KPU) or chronic laminitis.
Despite all the disadvantages, beet pulp is still fed very frequently, not least because of the massive marketing by feed manufacturers. It is advertised as a “grain-free concentrated feed” for horses that actually do not need any feed in the trough at all, for example because they are easy keepers or already overweight and do not get enough exercise in relation to the energy content of their forage ration.
Molasses
This is also a waste product from sugar production, which is produced during the processing of both sugar beet and sugar cane. Centrifugation to produce sugar produces molasses as a residual product, which still contains up to 60% sugar. Around 7 million tons of molasses are produced worldwide every year, most of which is used in animal feed as a pellet binder or flavoring ingredient. In Germany alone, around 530,000 tons of molasses are used in animal feed every year. The problem is not only the possible development of tooth decay (caries) in horses, but also the side-effect of molasses in mixed feeds as a breeding ground for bacteria, fungi and mites. For this reason, processed and molassed grains (e.g. corn, oat or barley flakes) must be preserved with large quantities of preservatives which have negative effects on the microbiome of the horse as well as the detoxification systems like liver and kindeys.
Waste from soybean processing
Soy hulls / soy extraction meal
Both are waste products from the processing of soybeans. At the beginning of the process, the beans are peeled. The soybean shells that fall off consist mainly of crude fiber (cellulose and pectins) and are used as a cheap filler in horse feed. After the oil has been extracted (pressed and ethanol extracted), the soybean extraction meal remains, which mainly consists of soy protein (50%). The trypsin inhibitors contained in soybeans prevent protein digestion, so soybean meal must always be treated with heat to inactivate the trypsin inhibitors. However, this also causes protein denaturation, which increases the risk of allergies. The other problem with soybeans and soybean (extraction) meal is its stachyose content. This polysaccharide cannot be digested in the small intestine but is transported into the hindgut. The microbial fermentation of Stachyosis leads to dysbiosis and in many horses to bloating, flatulence and even gas colic.
Soybean meal is usually added to mixed feed for sports horses as well as feeds for broodmares and growing horses because there is an increased need for protein. However, soy protein is of low quality for horses. Instead of building muscles, horses under soy protein feeding often “swell up” and become lymphatic. Virtually all that is available on the world market is GMO soy. These plants are highly resistant to the herbicide glyphosate which are applied in generous amounts during growth. These glyphosates, that can still be found in soybeans and residue products of soybean processing, enter the animals’ metabolism via the feed. There they damage the hindgut microbiome, inhibit liver enzymes, lead to increased creatinine kinase levels in the blood and increase glycogen storage in muscles, which is a problem especially in PSSM horses (which often receive grain-free mixed feeds based on soy products). Glyphosates are also known to chelate trace elements, which can promote mineral deficiency symptoms despite apparently good supply.
“Chaff”
One of the probably worst developments is the composition of mixed feeds with “plant fiber components”. These usually are 1 – 2 cm long pieces of chopped hay or alfalfa stalks (while the alfalfa leaves are often used in rodent feed, since they are even more profitable than horse feed). Chaff produces a large volume without having any significant energy or nutrient content. They are basically a cheap filler sold for high prices to the unknowing horse owner. Due to their low energy content (comparable to hay) they are particularly used in mixed feed for leisure horses and easy keepers in order to increase the volume in the feed bucket without the horses immediately becoming fat.
The frequently used marketing argument that adding chaff encourages better chewing performance has long been disproved in feeding studies. At the same time, it has been shown that chaff in the length between 1 and 7 centimeters is chewed poorly or not at all, since the horses use more of a pressing than a grinding movement when being fed chaff. When these poorly chewed fibers enter the digestive tract, they slow down the passage through the hindgut by triggering an anti-peristaltic wave in the ventral colon that transports the chaff-pieces back to the starting point over and over again. This leads to the chaff-fibers remaining in the hindgut for up to one week which provokes dysbiosis. Feeding chaff is now one of the most common causes of hindgut dysbiosis in otherwise well-fed horses.
Conclusion
During the times of industrialization and the world wars, horse feeding relied on waste materials in order to feed the horse at an affordable price. Today, the feed industry uses a whole range of food waste products in horse feeding in order to maximize its profit margin. Horse owners spend more money on their horses than ever before and receive feed of significantly poorer quality than if they were to limit themselves to the traditional feeding of plenty of hay, pasture grass and – in case of sport horses – a little oats or crushed barley, depending on performance. The developments in the feed industry have given us a range of “diseases of civilization” in horses, from equine metabolic syndrome (EMS) via atypical laminitis to sweet itch and various dental problems that would not exist at all with species-appropriate feeding and care.
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