Leading figures in the equine industry agree: The exposure of horses to mycotoxins, or toxins derived from mold, is a critical area requiring attention. All horses come into contact with mycotoxins on a daily basis, and while they can never be completely eliminated, good feed and management practices can reduce mycotoxin exposure.
How do mycotoxins impact horses?
Horses can be exposed to mycotoxins via feed materials, grazing, and bedding. Mycotoxins are produced by some types of mold growth under certain conditions. They can occur in growing, harvested or stored grain and forage crops.
Molds familiar to the equine industry include Rhizoctonia on clover, ergot toxins on ryegrass and grain, and Acremonium on fescue. These molds are challenging to eradicate. Their growth rates tend to increase when the plant is under stress due to extreme weather conditions or heavy grazing. The prevalence of mycotoxins is usually highest from plants grazed or harvested during a wet autumn following a dry summer.
Until recently, there has been limited research surrounding the effects of mycotoxins on horses, with data usually used from the swine or ruminant industries. It is somewhat challenging to use non-equine data effectively, as a horse is comparable to a ruminant in the role of a forage grazing animal but has a gastrointestinal tract more closely related to the pig. The addition of the hindgut fermentation process may also be a complication. The requirements for a horse are also significantly different from those for livestock species. The focus for equines is less on meat and milk production and more on conformation, temperament, performance, and durability.
Mycotoxins are a concern for horses because of the effects that consistent, low-level exposure may have on athletic performance and breeding capability without the appearance of any specific symptoms. Horses can also have a long lifespan and may, therefore, be expected to reproduce successfully in their later years. For this reason, the relative “safe” level of mycotoxins allowable within the equine diet is unknown.
Acute mycotoxicosis (mycotoxin poisoning) is rare. The more likely challenge for the horse is chronic mycotoxicosis, or exposure to low levels of multiple mycotoxins. Mycotoxicosis has the potential to suppress the immune system and has been associated with a wide range of conditions, from general lack of form hypersensitivity and loss of well-being to colic, liver damage, and even death. High-risk groups, include horses whose immune systems may already be under pressure: broodmares, young stock, veterans, performance horses, poor doers, or sick equids.
Feed management
Good management practices, such as using quality feedstuffs, careful production and storage of feedstuffs, and ensuring a fully balanced diet can help reduce mycotoxin exposure. Since many of the management practices that can reduce contamination occur during crop production and harvest, prevention is sometimes not an option for the majority of horse owners who do not produce their own feed.
kt
Grain
Horse grain in hand
Therefore, extra care should be taken when choosing feed to ensure ingredients have been stored and mixed appropriately. When storing feed at home or the yard, clean, dry, and water-tight containers should be used. They should be cleaned between feeds and should be vermin-proof. All feeding equipment and utensils should also be cleaned regularly and stored in a cool, dry area. Despite these precautions, contamination is often unavoidable. One option for dealing with this is to include a mycotoxin adsorbent in the horse’s diet, as it specifically binds mycotoxins and removes them from the gut. Traditionally, clay binders have been included in the diet for this purpose. However, they tend to have high dietary inclusion rates and can also bind key nutrients from the diet. Organic mycotoxin adsorbents, such as yeast cell-wall fractions, offer many advantages over the clay binders, including lower inclusion rates and rapid binding of mycotoxins—without binding key dietary nutrients. As such, many of these organic mycotoxin adsorbents can be used regularly used in a horse’s diet.
Pasture management
Grazing provides a significant source of both protein and energy. When considering pasture from a mycotoxin management standpoint, the proportion of pasture contributing to the overall diet should be taken into account. Grass tends to have the highest nutritional value in the early stages of growth, so getting the most out of a grazing system includes:
Rotating pastures. Allow time for each area to rest and regenerate some growth. Divide your current pasture into smaller sections with suitable fencing to allow sufficient time for grass recovery and plenty of opportunity to rotate animals and provide fresh pasture.
Mowing (topping) pastures. Stimulate development of new growth. However, this is only really feasible when there is sufficient old pasture growth. As horses tend to graze unevenly they create densely grazed patches over the pasture, which can encourage weed growth and render the field looking horse-sick. Horse-sick fields are at greater risk of mycotoxin contamination. Topping can encourage a more even re-growth of grass once horses have been removed. If you do not have the option to rotate horses, or if the pasture is too small to divide, designate a small area to feed hay while the pasture recovers. This will allow the majority of the pasture to recover. However, you must be aware of the amount of re-growth allowed before horses are re-introduced – large amounts of re-growth can increase the risk of issues, such as laminitis and obesity leading to impaired insulin metabolism.
Manure management. Horses generally designate specific areas to drop manure; these areas are naturally avoided for grazing. This can help to reduce parasite load, although worm larvae will travel a significant distance to find a healthy plant most likely to be consumed. Removal of manure from the pasture on a regular basis reduces not only the worm burden to the horse but also the additional stress of worm larvae to the grass plant. Both these points can help reduce the impact of mycotoxins. Co-grazing with other species, such as sheep, can also help to reduce the pasture parasite burden.
Undoubtedly, horses thrive in a situation where they have regular access to good pasture, not only due to nutrition but also physical and mental wellbeing. However, poor attention to detail when planning management of grazing pastures can significantly increase the risk of mycotoxin contamination.
Horses cannot avoid exposure to mycotoxins, but with good management practices and the dietary inclusion of a proven mycotoxin adsorbent, it is possible to significantly reduce mycotoxins’ potentially harmful effects.
About Dr. Helen Warren –
Dr. Warren achieved her primary degree in Animal Science from Aberystwyth University, Wales in 1999, followed by her PhD from the Faculty of Medical and Veterinary Sciences at Bristol University. She is a member of the British Society of Animal Science, a qualified lecturer and a registered Animal Scientist. She has lectured degree level students in equine nutrition, fitness and training and anatomy and physiology. She currently works as European Technical Manager for Alltech for both ruminants and horses, involving initiating European research projects, as well as delivering nutritional education and technical sales support.
For more information on mycotoxins, visit knowmycotoxins.com or Alltech.com, or contact your local Alltech sales representative.