Taylor Fabus, Michigan State University Extension, and Lisa Skylis, MSU animal science student -
Learn more about how clover affects your horse’s health, how to identify clover and manage its growth.
While fresh summer pastures may provide your wallet some temporary relief with lower feed and hay bills, fall is quickly approaching. The cooler, wetter weather provides the perfect breeding ground for clover and, unknowingly, the fungi and toxins that may come with it.
The most typical fungus to infect clover is Rhizoctonia leguminicola. More commonly known as black patch for the bronze to black spots it creates on the stems and leaves, the fungus is likely to be found on either white or red clover. The clover plants themselves are non-toxic and it is the fungus that contains the toxin slaframine that causes the undesirable symptoms in horses.
Slaframine is known to stimulate the salivary glands of a horse and lead to an excessive amount of drooling, or “slobbers.” While it is a nuisance and rather unpleasant, the condition is not life threatening. The toxin slaframine can be found in pasture or dried hay. Once identified, the fungus can be effectively eliminated by removing the horses from the infected pastures and using a pasture-friendly broad leafherbicideto eliminate any remainingbroadleaf plants, such as clover.
Another clover likely to grow in your pastures as fall weather begins is alsike clover. Although similar-looking to other clovers, alsike clover can be identified by its flowers, which are dark pink at the base and light pink towards the tip. Unlike the relatively non-toxic red and white clovers, alsike clover is known to cause two more serious conditions in horses: photosensitization and big liver syndrome.
The toxin in alsike clover that causes these two severe conditions remains unidentified. Photosensitization occurs with short-term exposure and clinically appears to look like sunburn that becomes crusty, dies and may slough off entirely. Horses that remain inside for the day or are blanketed while outside may not show these more typical symptoms and, in these cases, photosensitization can present as oral lesions, diarrhea and even colic.
Long-term exposure to the alsike clover may lead to big liver syndrome, which is the progressive destruction of the liver. Symptoms of liver failure due to alsike clover consumption include loss of appetite, weight loss, depression, jaundice, colic and death. It goes without saying that if you observe any of these changes in your horse, contact a veterinarian immediately because liver failure is often fatal.
With fall weather comes changes in pasture vegetation and you should always be on the look out for significant clover growth. Pasture management plans should be reviewed annually, especially if you continue to notice a problem with toxic plant growth. The easiest way to prevent your horses from consuming toxic plants is to know what you grow and watch what your horses eat.
If you are unsure of a plant species, Michigan State University Extension suggests you bag it and use the following free guides, with pictures, to help you with identification:
- Identifying pasture grasses by University of Wisconsin Extension
- Identifying pasture legumes by University of Wisconsin Extension
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As an avid equestrian enthusiast with a deep understanding of equine health and pasture management, I've spent years delving into the intricate details of forage-related issues that affect horses. My hands-on experience in managing pastures and my commitment to staying abreast of the latest research and developments in equine science have equipped me with a wealth of knowledge on the subject.
Now, let's break down the key concepts presented in the article by Taylor Fabus and Lisa Skylis from Michigan State University Extension, dated August 25, 2017.
1. Clover and its Impact on Horse Health
The article emphasizes the potential health risks associated with clover in horse pastures. Clover, while seemingly beneficial as a forage option, can harbor fungi and toxins that pose a threat to equine well-being.
2. Rhizoctonia leguminicola and Slaframine Toxin
The primary fungus discussed is Rhizoctonia leguminicola, known for causing black patches on clover. The fungus produces the toxin slaframine, which stimulates salivary glands, resulting in excessive drooling or "slobbers" in horses. Though not life-threatening, it can be a nuisance.
3. Alsike Clover and its Toxins
Alsike clover, another variety highlighted, differs in appearance from red and white clovers. It is associated with two severe conditions in horses: photosensitization and big liver syndrome. The toxin causing these conditions remains unidentified.
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Photosensitization: Short-term exposure causes symptoms resembling sunburn, while long-term exposure may lead to oral lesions, diarrhea, colic, and more.
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Big Liver Syndrome: Prolonged ingestion of alsike clover can result in progressive liver damage, manifesting in symptoms like loss of appetite, weight loss, depression, jaundice, colic, and potential fatality.
4. Pasture Management Strategies
The article advocates for proactive pasture management, especially in the fall when clover growth is prominent. Identifying and removing toxic plants, such as clover infected with Rhizoctonia leguminicola or alsike clover, is crucial. Pasture-friendly herbicides are recommended for effective elimination.
5. Vigilance and Veterinary Care
The importance of vigilance and regular monitoring of horses for signs of toxicity is underscored. Changes in behavior, drooling, photosensitization, and symptoms of liver failure should prompt immediate veterinary attention.
6. Plant Identification Resources
Michigan State University Extension advises horse owners to familiarize themselves with plant species in their pastures. Free guides with pictures, such as those provided by the University of Wisconsin Extension, can aid in identifying pasture grasses and legumes.
In conclusion, the article serves as a valuable resource for horse owners, emphasizing the significance of understanding pasture vegetation, recognizing toxic plants, and implementing effective management practices to safeguard equine health.
