In the world of horse nutrition’s, apple cider vinegar is one of the many pieces of advice and recommendations on how to improve the health and well-being of horses. Adding apple cider vinegar to the feed bowl is a recurring but highly controversial practice. Some claim that apple cider vinegar has a multitude of health benefits for horses, while others remain sceptical. But what actually is apple cider vinegar? What makes it different from other vinegars, such as wine vinegar? What does science say about feeding apple cider vinegar to horses? And of course: Can apple cider vinegar really “de-acidify” the horse?
What is apple cider vinegar?
Apple cider vinegar is a type of vinegar made from fermented apple must (cider). It is produced by the conversion of alcohol into acetic acid by acetic acid bacteria. The process of vinegar fermentation takes place when the apple cider comes into contact with vinegar bacteria and is fermented under certain temperature and aeration conditions.
In chemical terms, apple cider vinegar consists mainly of acetic acid and water. There are also a few other compounds such as flavonoids, phenols and minerals that come from the apples. The acetic acid is responsible for the characteristic sour flavour and is also said to be the active ingredient in the widely claimed health benefits of apple cider vinegar.
Compared to apple cider vinegar, other vinegars that are also popular in our kitchen, such as wine vinegar or balsamic vinegar, are made from wine. Wine vinegar is produced by fermenting wine with acetic acid bacteria, while balsamic vinegar is produced through a longer and more complex process of fermentation and ageing of grape must. Balsamic vinegar has a thicker consistency and a sweeter flavour compared to apple cider vinegar and wine vinegar.
From a chemical point of view, the vinegar types differ in their specific compositions and the proportions of the compounds they contain. Apple cider vinegar, for example, contains higher concentrations of phenols, while balsamic vinegar contains higher amounts of sugars and amino acids. Each variety has its own characteristic flavour and intended use in the kitchen. However, apple cider vinegar in particular is often said to have many healthy properties that are denied to other types of vinegar.
Scientists are ever so often investigating the health effects of apple cider vinegar. There are around 500 published studies on the subject, in which various effects have been investigated in different animals. When taken orally, apple cider vinegar is said to have positive effects on weight management in overweight people, help against insulin resistance and reduce the risk of cardiovascular disease.
What does science say about feeding apple cider vinegar to horses?
Many positive results can also be demonstrated in vitro, including the inhibition of cancer cell growth.
Unfortunately, however, an entire organism is much more complex than a cell culture, which is why these results cannot usually be reproduced in studies on laboratory animals or lead to unsatisfactory or inconclusive results overall.
At present, therefore, no clear positive effects on the health of the horse can be derived from the studies. All the claims that giving horses apple cider vinegar will magically make them lose weight, deworm them or make allergies disappear are unfortunately not tenable.
On the other hand, there are potential side effects. Apple cider vinegar still contains the vinegar bacteria that are required for its production. Vinegar bacteria are an inhomogeneous group of bacteria that are widespread in nature. They belong to the genus Acetobacter and some related genera. Humans have long utilised these bacteria for the production of vinegar, as they are able to convert ethanol (alcohol) into acetic acid.
Vinegar bacteria occur naturally on fruits, plants and in the environment. They are particularly common on fruit surfaces, such as grapes, apples, or berries, but can also be found in other fermented products such as wine or beer. Vinegar bacteria are aerobic organisms, which means that they require oxygen for their growth and metabolic activity. They carry out an oxidative fermentation in which they convert ethanol into acetic acid. This process takes place in the presence of oxygen, which is why acetic bacterial fermentations are carried out in open or ventilated containers.
What happens to apple cider vinegar in the horse’s large intestines?
Acetic acid and its salts (acetate) are also produced in the horse’s large intestine during the fermentation of cellulose and serve as a source of energy for the horse. According to current knowledge, the most important groups of bacteria involved in the production of acetic acid in the horse’s large intestine include members of the genera Ruminococcus, Fibrobacter and Lachnospirae. These bacterial species possess specialised enzymes that are able to efficiently break down cellulose and hemicellulose and support the fermentative processes for the production of acetic acid. They all require an anaerobic (= oxygen-free) environment, so they are completely different bacteria to those in apple cider vinegar, which live aerobically (= require oxygen).
It can be assumed that the vinegar bacteria from the apple cider vinegar cannot colonise in the horse’s large intestine due to a lack of oxygen. It is not possible to say whether and, if so, what effects the administration of apple cider vinegar or the passage of vinegar bacteria has on the horse’s large intestine microbiome, as there have been no reliable studies to date.
Can apple cider vinegar de-acidify the horse?
One of the most common uses for apple cider vinegar is to “de-acidify” the horse. As far as the pH value is concerned, vinegar bacteria are at their optimum in the acidic range. They prefer a pH value between 4 and 6, whereby a pH value around 5 is considered particularly favourable. In this range, they can convert ethanol into acetic acid most efficiently. Accordingly, apple cider vinegar usually has a pH value between 2.5 and 3.5. This highly acidic pH value is due to the acetic acid content, which is the main component of apple cider vinegar. Acetic acid is a weak acid among acids, which gives apple cider vinegar its characteristic sour flavour. The pH value can vary slightly depending on the exact composition and production method of the apple cider vinegar.
If the apple cider vinegar gets into the stomach, the front part of the stomach is acidified, as this is where pH values of 5-6 usually prevail. This can have a slightly negative effect on the stomach lining, especially if gastric ulcers or gastritis are already present. These are then irritated by the acetic acid, which can be painful for the horse. Fermentation reactions can also occur in this area, which could be one reason why some horses “burp” after being fed apple cider vinegar. This indicates considerable gas development in the front section of the stomach when the pressure becomes so great that the sphincter muscle at the entrance to the stomach allows gas to escape towards the mouth.
If the apple cider vinegar is transported onwards with the food bolus, the pH value at the back of the stomach does not change much, as it is already naturally at 2.5-3.5 in the area of the stomach outlet. When the food bolus enters the small intestine, it is then completely neutralised by buffer substances that come from the pancreas and liver and are added to the food bolus. This neutralises the acetic acid.
Trying to “de-acidify” connective tissue with apple cider vinegar cannot work in purely physiological terms. The pH neutralisation of apple cider vinegar takes place in the small intestine. Apple cider vinegar does not have an acid-neutralising function in the horse’s metabolism.
What can you do to de-acidify?
If you really want to de-acidify your horse, you should ensure that the microbiome (“intestinal flora”) in the large intestine is balanced. If incorrect fermentation occurs here, acids are permanently absorbed in excess, which can lead to the body’s natural ability to neutralise acids being overloaded. This can lead to the storage of acids in the connective tissue and subsequent lymphatic storage, which is then often interpreted as “fat”, although the horse is only lymphatic (pseudo-EMS).
You should also make sure you have a sufficient supply of zinc. This is because this important trace element is needed to activate the enzyme carbonic anhydrase in the metabolism, which is essentially responsible for the production of buffer substances to neutralise acids. A zinc deficiency can therefore also lead to hyperacidity of the connective tissue. Combined with detoxifying herbs and a balanced diet, weight loss can be achieved, and the body can restore its natural acid-base balance. Without vinegar, lemon juice or similar ineffective additives in the feed bowl.
External use
Apple cider vinegar is also used externally for and against a wide variety of problems. If you spray the horse with (diluted) apple cider vinegar to repel flies and midges, you are doing the horse a disservice.
Because acetic acid is produced when fruit ferments, many flying insects have receptors for it and fly specifically to the source. It is therefore more of an attractant for flying pests than a repellent.
Apple cider vinegar is only very likely to be helpful for external use in the hoof area. There are positive reports of its use against thrush and abscesses in the hoof area.
As you can see, not everything that is regarded as a “tried and tested household remedy” can actually fulfil its promise.
Sources
- Launholt, T. L., Kristiansen, C. B., & Hjorth, P. (2020). Safety and side effects of apple vinegar intake and its effect on metabolic parameters and body weight: a systematic review. European journal of nutrition, 59, 2273-2289.
- Chen, H., Chen, T., Giudici, P., & Chen, F. (2016). Vinegar functions on health: Constituents, sources, and formation mechanisms. Comprehensive Reviews in Food Science and Food Safety, 15(6), 1124-1138.
- Ousaaid, D., Mechchate, H., Laaroussi, H., Hano, C., Bakour, M., El Ghouizi, A., … & El Arabi, I. (2022). Fruits vinegar: Quality characteristics, phytochemistry, and functionality. Molecules, 27(1), 222.
- Ho, C. W., Lazim, A. M., Fazry, S., Zaki, U. K. H. H., & Lim, S. J. (2017). Varieties, production, composition and health benefits of vinegars: A review. Food chemistry, 221, 1621-1630.
- Guiné, R. P., Barroca, M. J., Coldea, T. E., Bartkiene, E., & Anjos, O. (2021). Apple fermented products: An overview of technology, properties and health effects. Processes, 9(2), 223.
- Stoltz, J. A. (2018). Literature review of three common equine hoof ailments. Journal of Undergraduate Studies at Trent (JUST), 6(1), 17-23.
- Mărgăoan, R., Cornea-Cipcigan, M., Topal, E., & Kösoğlu, M. (2020). Impact of fermentation processes on the bioactive profile and health-promoting properties of bee bread, mead and honey vinegar. Processes, 8(9), 1081.
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