Health Risk Hay

Written by Pferderevue
Thursday, October 27, 2016 — No Comments Yet

Why hay quality is decreasing and causing more coughing, colic, poisoning: horses are becoming ill because their hay is spoiled.

We address the question of why the quality of the most important basic fodder often leaves a lot to be desired.

Description: Gutes – im Sinne seiner botanischen Zusammensetzung und seines hygienischen Zustands – Heu ist das wichtigste Nahrungsmittel unserer Pferde. ©

Good - in the sense of its botanical composition and its hygienic condition - hay is the most important food of our horses. 

The case was hard to beat as a drama: ten "poisoned" horses in Andau gave left everyone guessing which evil criminal was capable of such cruel acts -and why. The horses had suffered from severe colic and been admitted to the University Hospital in Vienna. One horse did not survive the intestinal stasis and another had to be euthanized after the operation. The material damage was considerable. The subsequent criminal investigation led to the feed being analysed for toxic substances and the organs of the dead horses examined. No results. Finally, the Austrian Agency for Health and Food Security (AGES) found the culprit: the horses’ hay had been the cause, or, more correctly, the yeast and moulds found in the hay bales was at such high concentrations that the hay was unsuitable as a feed.


Although it is known that unhygienic hay can lead to serious health problems, it is rare to be shown how vitally important good quality basic fodder is. Colics associated with spoiled hay are not a rarity, as Univ.-Prof. Dr. René van den Hoven, Head of the Department of Internal Medicine at the University of Veterinary Medicine Vienna, knows. And unfortunately, both producer, keeper and horse owner are too little concerned with the quality of the most important horse feed, as the thesis ("Knowledge and Awareness in the Quality of Feed") of Charlotte Deininger revealed (see PR 4/2014).


Hay Quality is Declining

One of the reasons for this lack of interest is certainly the large number of supplementary feeds that are released year after year. It is often forgotten that high-quality and hygienically perfect hay is the foundation of horse feeding. "It is really bad about the quality of the hay for horses. This is an up-to-date topic where you have to start urgently, because horses are suffering," says Dipl.-Ing. Univ.Doz. Dr. Karl Buchgraber, Head of the Institute for Crop Production and Cultivation at HBLFA Raumberg-Gumpenstein and lecturer at the University of Bozen-Bolzano and the University of Veterinary Medicine Vienna. In his research, Dr. Buchgraber is constantly intensively studying hay as a feed for horses. And with this, the question why hay quality is getting worse and worse.

Description: © pholidito -

© pholidito -

One Problem, Many Answers

In hay, one should distinguish between two different quality criteria: the botanical and hygienic quality of the hay. The hygienic quality of the hay depends on the number of germs, bacteria and fungi. The primary cause of health problems are hygienic impurities of the hay. Through fungi and germs, the horses’ intestines are distended with gas as in the case of the dead horses of Andau. The botanical quality is the nutritional value of the hay. In other words: the variety of grasses and herbs, the minerals, the protein content and the nutrients.


On the question of whether and why the quality of the hay diminishes, opinions are divided—in the horse world and even more strongly in agriculture. All experts are in agreement that hay quality is increasingly an explosive issue. Only the causes and possible solutions seem to be not yet sufficiently clarified. Dr. Buchgraber sees a great problem in the ignorance of the stable owner. "Partly the quality of the hay is very bad at all yards without an agricultural background. People are only interested in the price, never the quality. "


Many riding stables no longer have an agricultural background. As a result, they do not produce hay themselves, but buy it from external suppliers. And as is true elsewhere in the free market economy, demand also determines the price: If the employer is too disinterested or too ignorant to question the hay quality, there is a risk that this will be compromised. Or that good quality is not appreciated and correspondingly honoured. Either way, a quality spiral is developing downwards. Raising Consciousness of the problem is therefore the first step on the way to better basic fodder.


Another reason for bad hay lies, according to the author, with the hay producers themselves. The correct production method is the decisive factor. Many farmers and growers either mow too early or too late, or even leave the cut grass to dry for a long time in the field. If the cut were too long on the field, it would pale, if it were too early, the hay would remain watery and damp, and immediately begin to rot when stored.


Another problem is the often too deep cut: in order to get more yield, some producers set the mower too deep. Thus, contaminants that are close to the ground can enter the hay and cause serious allergic reactions and respiratory problems in the horse. If soil is mixed with mown grass during harvest, drying is made very difficult. A cutting height of at least 5 to 7 cm must be observed.

Description: Heu Ernte Ballen Futter ©


Prof. van den Hoven, too, confers on the hay producers a certain responsibility for the poor developments in hay: "There is a lack of knowledge on how to produce good hay for horses." According to van den Hoven, farmers should be trained more Quality hay for horses is produced and they are especially clear that there is a big difference between feed for cattle and feed for horses.


Dr Peter Zechner, breeder and horse expert, is sure that the energy and protein content, and above all the sugar content for horses, is much too high for hay dried by equipment, which is now increasingly used in hay production. The same does not apply to ventilation hay.


Another important factor, which should not be ignored, is environmental influences. Summer 2013 was especially problematic for the production of the crop. Due to the long drought, farmers were able to mow only once, compared to two to three cuts in a normal year. This means, of course, a high loss of income and also hurts the quality of the hay.


Another problem that both René van den Hoven and Johann Krammel, chairman of the Heubörse association in the Viennese Forest, see very critically is the decline in cattle farmers as well as the prohibition of fertilizers. By both measures, meadows become less fertilized, which causes an advance of the Autumn Crocus. If the flowers or seeds of this plant get into the hay, this can have dramatic consequences for the horse: from bloody diarrhoea to death through respiratory paralysis, the consequences of a poisoning by Autumn Crocus are by no means easy to bear. If, on the other hand, farmers were to fertilize more or keep animals that fertilise the meadows, this poisonous plant could not spread further. "The Autumn Crocus tolerates no high nitrogen content through fertilizer," explains Krammel of the hay barn, which stands for high-quality hay in the Wienerwald.


It is also important to leave the hay for a few weeks after harvesting. "Hay and to a certain extent also straw during and after the harvest go through a 'sweat phase', which lasts six to eight weeks. During this time the harvested material must not be fed due to high microbial activity. The microbes produce heat through their metabolism in the haystack, which in moist hay can cause spontaneous combustion in the hay. Water emanates from the warming haystack, which must be able to evaporate. Hay which is very tightly packed or covered with plastic film cannot breathe and remains mainly moist in the centre- with the result that mould-forming agents form.


From this point of view, large bales are much less positive than small bales. This can be especially problematic with large round bales, "says Prof. Dr. Ellen Kienzle, who holds the Chair for Animal Nutrition and Dietetics at the Ludwig Maximilian University in Munich. According to Dr. Peter Zechner in his book "Everything for a horse-holder", round bales should be stored in a standing position, since the chimney effect, which results from this, optimizes the post-sweating phase. "For this, the bales have to be stored on a double floor (eg on wooden pallets) [...]." In general hay should not be used with the highest possible pressure. The ideal solution would be a fixed chamber press, which leaves a soft core. "For square bales, which are also used, the moisture content of the crop must be extremely low," says Dr. Zechner.


Storage of the hay plays a decisive role in its quality. According to Krammel, the hay is frequently high quality, but is stored improperly by the end user. Even the best hay is able to absorb very high amounts of moisture very quickly and absorb moisture when wet. This is the reason for its hygienic quality, and it can no longer be used as feed. Kienzle: "In many places it is customary to store large bales outdoors. This is not recommended. Even if the storage space is covered, changing humidity and temperatures force moisture into the bales. This promotes the growth of moulds. In the open, many different sort of fungi such as the toxin-forming Fusarium find good conditions for growth.


The open-air storage of large bales without cover is catastrophic, in which the obviously corrupt outer layer is thrown away and the core is fed. Here it can easily happen that the microbial activity is highest in the core, which is not yet completely corrupted, whereas in the corrupted outer layer there are mainly dead fungi. But these are still allergenic. "


Good Hay, Bad Hay

According to the experts, the quality of hay depends on many factors: the location, the time of mowing, the environmental conditions, the fertilization, the correct drying and finally the correct storage. And mistakes can happen everywhere or the quality can be negatively affected by negligence. On the question of how good hay can be recognised, all experts are in agreement: optically and olfactically it should be appealing. A layman without special expertise could quickly recognize the quality of the hay. It is said to have a fresh green tint, to smell of hay, not of mould. When touching it should feel rough and dry. And if you throw it into the air, it should not drop dust. If the colour of the hay has faded, this indicates too long dried or often wet hay. If it is brown or black, the temperature in the dry phase was too high. In both cases, the hay is lacking in nutrients and it can even lead to liver and brain damage, laminitis and asthma. If the hay also has a musty smell, this indicates a mould infection and it should not be fed. The result would be severe health problems. If the hay feels slightly moist or clammy, this indicates a too high moisture content. This can be caused by a too short sweating phase of the hay or by non-appropriate storage. Even in this case the hay should not be fed.

Description: Heu aus dem ersten Schnitt hat einen höheren Rohfasergehalt und wird von Pferden bevorzugt. Doch auch ein Zuviel an Rohfaser ist nicht gut. © Elke Hellmich

Hay from the first cut has a higher crude fibre content and is preferred by horses. But too much raw fibre is not good. Woody, bulky hay can also promote the development of laminitis in addition to colic maturity, increased sensitivity to diarrhoea and drought.
© Elke Hellmich

If you want to be a conscientious horse owner, do not only rely on your own senses, but err on the side of caution. Johann Krammel recommends that you carry out a moisture measurement in the bale. According to Dr. Buchgraber, high-quality hay should not have more than 14% moisture content after harvesting (after drying on the field), otherwise it would quickly mould. Probably the safest method for determining the hay quality is analysis in a feed laboratory. There the hay is examined for bacteria and fungi. "If one suspects that the hay is spoiled, test it immediately!," says veterinarian Dr. Bernadette Linsbichler. Until the result of such an investigation is known, however, about two weeks pass - as an immediate measure it is thus unsuitable. In the case of suspicion, therefore, do not feed the bale.

Description: Heu aus dem (späten) zweiten Schnitt ist aromatischer und feiner, sein Energiegehalt ist höher. © Elke Hellmich

Heu aus dem (späten) zweiten Schnitt ist aromatischer und feiner, sein Energiegehalt ist höher. 
© Elke Hellmich


Health Risk

Poor hay quality can cause a variety of acute and chronic diseases in horses. To portray the horse as particularly susceptible or sensitive is fundamentally wrong, emphasizes Buchgraber. "A horse ingests up to ten billion spores per day. In the long term no one would remain healthy with this strain of microorganisms. "


An increasingly serious problem are respiratory diseases such as various forms of bronchitis and, in the worst case, Recurrent Airway Obstruction (RAO). This disease is an allergic reaction which can be triggered by fungal spores in the hay and is maintained by dust. Small amounts of allergens are sufficient to keep the disease going. RAO manifests itself in a chronic cough, which can lead to pneumonia in the worst case. "I have more RAO patients every year - and this is very much linked to lack of hygiene and poor quality of hay," says Dr. Linsbichler.


Serious problems can also arise in ​​the digestive tract: gastric ulcers, weight loss and throat problems or severe Colics can be caused by a lack of hay quality and, in the worst case, by toxins contained in hay, even fatal. Professor van den Hoven points out that there are other serious chronic diseases that may be associated with poor quality of hay: "Bone problems and calcifications of the aortae by hay contaminated with gold beetles do not occur frequently, but we have had quite a few cases."


Of course, the quality of the hay can also be basically in order, but the fodder contains poisonous plants like the Autumn Crocus. Although most horses generally avoid the bad tasting plant, there are instances where horses still eat the poisonous plant. According to van den Hoven, this leads to poisoning and in some cases the death of the animal.


Improperly produced hay also contains much fewer nutrients than high-quality hay. This can lead to a lack of nutrients in horses, and the animals subsequently lose weight. Since horses are often fed with feed and minerals, the nutrient deficiency of hay is not noticed at all. However, this does not alter the fact that the poor quality of the hay can only lead to chronic diseases only years later. Both Dr. Linsbichler and Prof. van den Hoven agree that in some cases horses can live well with inferior hay for years without developing diseases. This is comparable to people who are poorly nourished for years and remain healthy during that time. But it always depends on the individual physical condition - and usually bad nutrition has its revenge in old age and this is also true in the horse. How many horses are treated annually due to feeding-related diseases is difficult to assess, because the precise causes of the disease remain unclear to some extent. Prof. van den Hoven confirms what was already stated by Prof. Helmut Meyer in the 1970s in his standard work on horse feeding: the poor hygienic quality of the hay is a common but not the only cause of colic.

Description: Schimmeliges Heu wie dieses darf auf keinen Fall mehr verfüttert werden! © Lothar Lenz

Schimmeliges Heu wie dieses darf auf keinen Fall mehr verfüttert werden! 
© Lothar Lenz



"Awareness must be heightened first," says Buchgraber. For farmers, for horse-owners, for liveries. As a single horse owner in a large riding stables, it often seems that you are at the mercy of the yard management in terms of feeding. Apart from the desired amount of hay, there is not much you can dictate there. Nevertheless, as a horse owner, you should not accept anything but make yourself acquainted with their practices and check the feed regularly. Major problems can also be detected without laboratory analysis. Farmers, according to Buchgraber, are more aware of the responsibility they bear in the production of hay. "We have just carried out an investigation: Most farmers are very likely to believe that they produce good quality," says Buchgraber.


Farmers should check their work, possibly even have the hay checked by a feed merchant. But the biggest responsibility still lies with the yard owners. At the end of the day it is their decision from whom they obtain their hay. "At the time of the delivery, the quality should be checked at random.  By new deliveries there should  still be enough old hay or straw that it is possible to reject a delivery without the risk of being left with no hay or straw until a replacement delivery arrives, "advises Ellen Kienzle. And last but not least, the price is also a reference to quality: he who buys cheap, must be aware that good quality has its price, which should be paid for fairly. Once the awareness of the importance of good feed is raised, then additional costs can also be better accepted by horse owners. Really cheap is not cheap anyway—considering the numerous possible follow-up costs. The principle for horses is the same as for humans: you are what you eat.



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