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Feeding Clover to Horses: Slobber, Clover Toxicity, and Horse Health

Feeding Clover to Horses: Slobber, Clover Toxicity, and Horse Health

Feeding Clover to Horses: Slobber, Clover Poisoning, and Horse Health

Clover, a common legume plant found in pastures, is often a part of many horses' diets. While clover can provide significant nutritional benefits, excessive consumption or the presence of certain types of clover can lead to health problems in horses. In this blog post, we delve into the world of feeding clover to your horse, looking at the good, the bad, and the slobbery. Clover, particularly red and white clover, is a nitrogen-fixing plant known for its high nutritional value. However, significant clover growth in your pasture mix can sometimes pose risks for horse health, depending on the species. 

Nutritional Value

Clover, in its different varieties, including red, white, and sweet, can be a valuable addition to the diet of horses due to its high nutritional value. It is a rich source of essential nutrients, providing a balanced ratio of protein, fiber, and energy.

Protein is a critical component of a horse's diet, and clover, especially red and white, is known to have a higher protein content than most grasses found in pastures. This protein helps in supporting muscle growth and repair, making clover an excellent choice for performance horses or those in rigorous training.

Clover is also high in fiber which aids in the smooth functioning of a horse's digestive system. Horses, being hindgut fermenters, rely on fiber-rich diets to maintain gastrointestinal health. Furthermore, clover is a significant source of energy, which can support the horse's activity levels and overall vitality.

In addition to these macronutrients, clover is a good source of essential vitamins and minerals, including Vitamin A, Vitamin C, calcium, and phosphorus. Vitamin A is necessary for maintaining good vision, a healthy immune system, and proper growth, while Vitamin C acts as an antioxidant. Calcium and phosphorus are necessary for the healthy development of bones and teeth.

Clover also plays a role in pasture health. As a nitrogen-fixing plant, clover can contribute to soil fertility, promoting the growth of other nutritious grass species in the pasture.

Red Clover & White Clover: Cause for Excessive Slobber or Drool

Red and white clovers (Trifolium pratense and Trifolium repens) are commonly found in pastures and are generally safe for horses. However, a fungus called Rhizoctonia leguminicola, commonly referred to as "black patch," can infect these plants. This fungus is characterized by the bronze to black spots it forms on the stems and leaves of the clover. It can infect both white and red clover, introducing a toxin into an otherwise non-toxic plant.

The toxin introduced by this fungus is called slaframine. This substance has a specific effect on horses—it stimulates their salivary glands, resulting in an excessive amount of drooling, a condition colloquially known as "slobbers." While the sight of a horse with slobbers may be somewhat unpleasant and cause concern, it's important to note that this condition is not life-threatening.

Slaframine can be present in both fresh clover in the pasture and in dried clover hay. Therefore, horse owners need to be vigilant about their animals' food sources to avoid this condition, whether horses are grazing in the field or eating stored fodder. Despite the unpleasant symptoms it causes, slaframine's effects are more of an inconvenience than a serious threat to a horse's health.

Alsike Clover: Cause for Serious Clover Toxicity

Unlike red clover or white clover, which are typically benign for horses, certain types of clover like alsike pose more significant health risks. Alsike clover (Trifolium hybridum) is known to cause severe conditions such as photosensitization and big liver syndrome in horses.

The specific toxin in alsike clover that triggers these conditions remains unknown. Photosensitization, which can resemble a sunburn that becomes crusty and may eventually shed, can result from short-term exposure. Horses kept indoors during daylight hours or those covered while outside may not exhibit these common symptoms. In such instances, photosensitization can manifest as oral lesions, diarrhea, or even colic.

Chronic exposure to alsike clover can precipitate big liver syndrome, characterized by progressive liver damage. Symptoms of liver failure or liver disease due to consumption of this toxic clover include loss of appetite, weight loss, depression, jaundice, colic, and in the worst cases, death. For these reasons, it's best to prevent horses from consuming toxic alsike clover in the pasture by treating the field with a pasture-friendly broad leaf herbicide and replanting the pasture altogether. Horses with symptoms suggestive of alsike clover toxicity need to be immediately treated by the veterinarian. 

Sweet Clover: Cause for Clover Poisoning from Fungus

Sweet clover (Melilotus officinalis) can be an important component of the diet for many horses. However, when improperly stored and allowed to mold, it can also be the source of a serious health concern.

In the 1920s, North American cattle suffered from a fatal hemorrhagic disease linked to moldy sweet clover hay or silage. Investigations pointed to the conversion of the harmless coumarins found in sweet clover to a toxic compound called dicumarol. This occurs when the sweet clover is stored in conditions conducive to molding. Dicumarol acts as a powerful anticoagulant, interfering with the synthesis of essential proteins necessary for blood clotting in animals.

When horses and other animals consume hay containing high concentrations of dicumarol over several weeks, the resulting condition, known as sweet clover poisoning, can develop. Symptoms include stiff or lame movements due to bleeding into muscles and joints, hematoma, and gastrointestinal bleeding. Often, the first indication of dicumarol poisoning might be the sudden death of one or more animals in the herd.

The most foolproof way to prevent sweet clover poisoning is to avoid feeding horses sweet clover hay or silage that has not been properly stored. 

Effective Pasture Management: Keeping Your Horses Safe

This information underlines the importance of pasture management, including monitoring clover growth and identifying any infected clover. While clover, being a nitrogen-fixing plant, can be a beneficial part of a pasture mix and a good source for horses, problems arise when the percentage of clover in the pasture increases significantly.

Feeding clover to your horse can be a part of a balanced diet, but careful watch of what your horses eat and preventing them from consuming toxic clovers is crucial. Certain conditions in horses can arise from changes in pasture vegetation or the presence of moldy clover in their diet.

Clover poisoning in horses varies based on the type of clover and the individual horse's preferences for clover. For example, alsike clover toxicity needs immediate veterinary attention. Horses displaying signs suggestive of alsike clover toxicity should be taken seriously. However, the excessive salivation caused by white and red clover plants effects on the salivary glands, is more of a nuisance than a real threat to your horse's health. 

In conclusion, horse health is closely tied to pasture use, and managing clover for horses involves keeping a close eye on clover consumption, removing clover plant from your pasture when necessary, and implementing pasture management plans to ensure a healthy mix of species in the pasture. The overall goal is maintaining a healthy and safe grazing environment for horses and ponies.


  • Kevin Lowery

    Is there anything you can use to treat the bales of hay that has Black Patch or Slaframine so that it can be fed to horses to minimize the slobbering?

  • Marsha Vider

    Thank you for the info. It answered all my questions and some I didn’t have in the beginning.. Again thanks for the update.

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