Why is silage bad for horses

Silage - the unfodder

Feeding haylage and silage to horses

The silage or haylage feeding of horses is hotly debated. Rightly so. Hardly any other food has so many disadvantages with so few advantages.

The use of silage in factory farming, a harvest independent of the weather and the simple storage of the silage bales even in open areas has tempted many farmers to feed silage or haylage to horses. This trend was even supported at animal colleges without any further education about the nutritional disadvantages of this form of preservation.

Silage is frowned upon even in cattle farming

It is now known even from cattle farming that silage can have negative effects on the quality of meat, milk and cheese as well as the health of the calves. There is also a trend among consumers towards hay milk and hay milk products.

The fact that the feeding of ensiled roughage is still practiced on horses is of the utmost concern, especially in the rearing of horses.

Horses like to eat silage or haylage and represent an alternative to poor quality hay. For dust-allergic horses, dust-free silage often seems to be the last resort. It is also rich in leaves and therefore rich in trace elements, minerals and energy.

The requirement expressed by feeding experts that silage should only be produced and fed by competent persons shows that this is a not entirely unproblematic feed. Silage production is a matter of the utmost care and conscientiousness. Deviations from the procedure, inaccuracies or non-observance of certain procedures lead to a deterioration in quality and even to spoilage, which under certain circumstances can cost the feed animal its life.

Since the topic of silage is discussed in a highly emotional and controversial manner, it should be dealt with scientifically in order to then weigh up. A little background information is important for this.

Silage - grass preserved for the winter

If you just cut grass and left it, it would rot. Therefore, in haymaking, the grass is dried with the help of the sun after the cut and turned until a dry matter content of 85 percent is reached. If the residual moisture is below 15 percent, spoilage is stopped. Bad weather turns haymaking into a fiasco. Nutrients are washed out and the additional turning of the hay results in a loss of crumbling, in particular loss of leaves and thus of minerals and trace elements. Not completely dried hay tends to form mold and is unsuitable for feeding.

This is where silage shows its advantages. Silage is made from grass (grass silage), dried grass (haylage) or chopped maize plants (maize silage) regardless of the weather.

Grass silage or haylage

The grass silage unsuitable for horse feeding is cut before flowering (or as a second cut) and left in the field for about half a day to a day. Then it is pressed like hay and packed airtight. The grass silage is reserved for cattle feed due to its high protein content, low crude fiber content and residual moisture of 60 to 65 percent.

In general, it is haylage that is fed to horses, also called “fermenting hay”. It has a higher dry matter content than grass silage. After flowering, the grass is cut and dried before it is wrapped in bales. The bulky cuttings of the haylage must be pressed more tightly than that of the grass silage, because no air spaces are allowed. Silage aids or lactic acid bacteria additives are mandatory!

Then the silage must be wrapped several times with plastic film so that no air exchange with the environment takes place. The haylage has a residual moisture content of 30 to 50 percent. However, the lower dry matter content must be taken into account when determining the amount of feed. In terms of quantity, significantly more silage than hay has to be fed in order to achieve the same crude fiber content. The disadvantages and also the dangers of the haylage become apparent on closer inspection of the ensiling process.

The secret of the ensiling process

During the ensiling process, the dried grass is deprived of oxygen by the activity of microorganisms.

The more "airy" the silage is packed (for example, due to the bulkiness of dried overhanging grass in haylage production), the longer there is the possibility that aerobic germs, including undesired yeasts, will produce acetic acid, carbon dioxide and alcohol.

An anaerobic environment is only created after complete breathing and fermentation under absolute exclusion of air. Only microorganisms that can live without oxygen feel comfortable here. Lactic acid bacteria, which can multiply without oxygen and contribute to a rapid drop in the pH value, are highly desirable in ensiling.

All other microorganisms are called fermentation feed pests. The lactic acid bacteria use the grape sugar (glucose) from the plant and convert it directly into lactic acid. Depending on the duration of the fermentation, incorrectly pressed cavities or packaging errors, acetic acid, alcohol or butyric acid are produced in addition to lactic acid (the stinking butyric acid is an indication of the activity of clostridia, for example).

Air exclusion required

As part of the oxygen-free (anaerobic) climate created in the packaging, the germs that require oxygen, including yeasts and bacteria, die. This stops the spoilage from spoiling and from now on one speaks of fermentation, which starts with the help of anaerobic germs. The grass clippings are quickly acidified by the three types of acidifying agents, the lactic, butyric and acetic acid bacteria, which then multiply rapidly. In the course of fermentation, the ratio in the silage shifts in favor of the lactic acid producers. The process takes about two to three days.

The secret of good preservation lies in the rapid development of lactic acid producers and the resulting rapid acidification of the silage. The fermentation by the lactic acid-producing bacteria ends when the low pH value has now been reached or when the sugar is completely used up. Acidification that is too slow and a high sugar content support the formation of alcohol by yeast. Rapid acidification, on the other hand, robs the dangerous clostridia of life.

Silage is acidic feed

Acid formation is crucial for the quality of the silage. The resulting lactic acid acidifies the silage. If the pH value falls below 4.8, putrefactive germs die. The dangerous, pathogenic clostridia only die from a pH value of 4.2 to 4.4, which is important to know because Heulage often does not reach this value!

During the two-week main fermentation phase, the pH value continues to decrease. The lactic acid producers remain active up to a pH value of 3. The fermentation process ends either because of a low pH value or because there are no more fermentable carbohydrates available. Ideally, the ensiling is now complete and the product can be kept all year round.

Anyone who feeds fully fermented silage must, however, know that they are feeding their horse an acidic feed. The constant supply of acid with the basic feed is a significant attack on the body's own sodium bicarbonate reserves, which serve to deacidify the body. Silage feeding leads to a continuous acidification of the organism. The body needs various minerals and trace elements to neutralize acids. This could lead to a creeping form of demineralization - not only in young horses. Many horses react to excessive acid intake with tension and muscle cramps. Anyone who feeds haylage that has not reached the pH value of 4.2 and feels confident not to feed such acidic feed runs the risk of their horse suffering from clostridial poisoning, which is often fatal.

Problems with ensiling

If the packaging of the silage is damaged, atmospheric oxygen enters the silage. Yeasts and aerobic bacteria develop rapidly and break down lactic acid in the process. The resulting increase in pH leads to spoilage. The silage bale must be discarded.

Another danger is that if the pressure is too low, oxygen-loving germs will survive and multiply. The silage spoils. Digestive disorders such as diarrhea and colic occur in the feed animal. In order to avoid air spaces, the bulky haylage must be pressed with particularly high pressure. Carelessness can be fatal.

Danger from Clostridium botulinum in haylage

If it is not possible to quickly ferment the silage acidic and to reach the critical pH value, which is rarely reached in haylage, clostridia multiply. These are bacteria that produce a poison called botulin. Botulin inhibits signal transmission from nerve cells and has a muscle-paralyzing effect. The poisoning with botulism, the so-called botulism, manifests itself in the horse in paralysis and severe colic, in which the bacterial toxin is too often overlooked as the actual trigger.

Clostridia live in the ground and multiply particularly well in the absence of air, especially in the presence of protein-rich animal carcasses (snails, birds or small mammals). Very few farmers or their employees make the effort to walk into the ground immediately before mowing in order to scare away small animals such as hares, rabbits or deer so that their carcasses are not shredded later and wrapped in the film.

There is no longer any time to search the clippings for rubbish, twigs, carcasses and other debris after swathing and before baling. In addition, it is not uncommon for the cuttings to be cut too close to the surface of the soil, so that clostridial soil gets into the silage. In the absence of air and acidification that is too slow, there is a risk of contamination.

Clostridia convert protein and lactic acid into biogenic amino acids and butyric acid. The butyric acid smells like cheese or stink bombs. Since lactic acid, on the other hand, is odorless, silage should always smell pleasant. An unpleasant smell is therefore an indication of incorrect fermentation (e.g. due to pressing with too little pressure).

Due to the potential danger of infection with botulism due to the presence of clostridia, both silage and haylage are strongly discouraged in horses. Ruminants such as cows have a better chance of dealing with harmful bacteria and their poisons than horses.

Reactions that are harmful to health from feeding silage

One of the main reasons not to feed either silage or haylage to cattle or horses is the fact that any fermentation of protein-containing feed is caused by bacteria, fungi or yeasts Biogenic amines comes.

Quite a few horses react to silage feeding and the associated supply of not small amounts of biogenic amines with diarrhea, flatulence, colic and even cardiovascular diseases, which can be recognized by tarnished legs (front and back).

Horses and cows are not scavengers

The allergic, catarrhal reactions that prevail histamine (the best known biogenic amine) have an enormous negative impact on the health of non-scavengers.

In silage exactly the prerequisites are given to biogenic amines (also Putrescine, cadaverine, better known as cadaveric poisons, but also Tyraminewhich causes the smooth muscles to contract), depending on the total amount of protein, the type of microorganisms present and sufficient time to form.

See below: Representation of the molecule of the biogenic amine cadaverine, arising from the amino acid lysine:

The more problematic or unclean the fermentation, the more histamine is formed by microorganisms.

The liver is responsible for breaking down biogenic amines. Long-term feeding of silage to horses inevitably leads to liver overload, liver problems and thus to disorders of the immune system, growth depression, hormonal disorders and impaired muscle building. This opens the door to diseases such as equine metabolic syndrome, equine Cushing's syndrome, laminitis and respiratory diseases!

The amount of histamine formed can only be kept within limits by a rapid, non-fermentation-free ensiling process. Silage without biogenic amines, however, is impossible! Nothing can be argued away from that.

Therefore, if one puts it in an exaggerated way, the feeding of silage to young horses can be compared to giving alcohol to young children. Both cause long-term damage to the liver and sustainably inhibit development, the immune system and bone formation.

Expertise, conscientiousness and caution are required

The production of silage requires a lot of knowledge, great skill and extreme caution. In order to avoid incorrect fermentation at first, you should work with increased pressure and flawless, airtight, double wrapping foil layers. The grass should be mowed slowly to allow small animals to escape. The soil uptake could be reduced with a harvest well above the ground. Both measures would prevent massive clostridial infestation.

Silage aids based on propionic acid, which are injected during wrapping, have proven to be very effective in improving quality. In principle, however, the presence of histamine and the high acid content of silage can hardly be changed. The latter should be countered with a corresponding mineralization in the rest of the feed. To compensate for this, alternating hay and at least straw litter should be provided.

Bales of haylage must always be shaken up and checked for foreign bodies and odors before feeding or ration allocation. Once opened, haylage bales should be used up within around two days, depending on the temperature. Secondary fermentation can begin through the air admission. In the event of mold formation, carcasses and a strong smell of butyric acid, the entire bale should be discarded.

Hay is and will remain the number 1 horse feed

In conclusion, it can be said that the silage, which was once highly praised even by veterinarians, is absolutely no horse feed. Good hay is and remains the basis for healthy feeding of a horse. The horse and its owner must not suffer from comfortable and misunderstood agricultural handling. Alternatives to very bad hay and silage are the feeding of meadow cobs and straw as roughage suppliers.

If you are more technically interested, I recommend Jeroch, Drochner and Simon "Nutrition of Agricultural Livestock", published in 1999 by Ulmer Verlag, Stuttgart.


Dr. Susanne Weyrauch 2010 (revised 2018) ©