I recently received a call from a fellow wanting to know how to get rid of the clover in his horse pasture. He had read online that clover was bad for horses. While I do really like the internet and all the valuable information it allows us to share, sometimes we do not get the whole picture. Additionally, regional differences can be very significant, so localizing the information you find online is also important.
Bottom line up front. Clover in moderate amounts is beneficial in horse pasture and hay. Clover is palatable, high-quality forage (often greater than 18 percent protein), and it fixes nitrogen in the soil. Some clovers in other parts of the U.S. have been associated with several health issues in horses when it exceeds 20 percent to 40 percent of a forage stand and becomes infected with fungal pathogens. However, due to our climate here in central Oklahoma, it remains to be seen if these health issues will occur.
The clovers often associated with health issues include alsike, sweet, red, and white. Sweet clover is often found on roadsides and was commonly grown for erosion control, honey production, and forage. Its downfall was its tendency to cause excessive bleeding in livestock when sweet clover hay became moldy. Alsike clover and to a lesser extent other legumes have been linked to photosensitivity skin reactions and liver disease. However, there seems to be some conflicting information as to whether this is caused by the clover itself or a fungus that also causes Black Blotch Disease (Cymodothea trifolii). White and red clover are associated with temporary, excessive salivation commonly called ‘slobbers’ when the clovers are colonized by the fungus Rhizoctonia leguminicola. It is considered to be largely harmless; although, a consult with a veterinarian or at least keeping a close eye on the affected horse is advisable. Dehydration, hoof issues and more severe issues are possible though rare.
If you notice, all of these health issues are associated with some kind of fungus. They are more likely to occur in pastures with large amounts of clover. They are also more likely to occur in wet, humid springs like the one we are experiencing now.
You may also come across information stating that clovers can cause colic, but that typically occurs in horses not properly acclimated to clover pasture. Keep in mind horses can colic on lush spring grasses as well. This is another reason to have a well-designed dry lot to control pasture access.
Many pastures have annual clovers like crimson and arrowleaf seeded into them. Unfortunately, there is little information about whether these clovers create the same problems as red, white, and alsike perennial clovers.
Keeping all this in mind, how worried should we be about the presence of clover in our pastures? Just because your horses have never experienced one of the mentioned health issues, doesn’t mean that they will not in the future. While the likelihood and risk of any of these causing death is very low, for some horse owners, it still is not as good as no risk at all. Then again, there is no such thing as a zero risk pasture or farm for that matter.
Ultimately, the goal is not to eliminate clover from a horse pasture. As stated earlier, it is beneficial in moderate amounts. Instead, we are looking to manage it, and knowing which type(s) of clover we have is the first step in managing the risk of health issues. This will not only give us an idea of problems to look for in our horses but also how to manage our pasture to prevent issues. Monitoring the amount of clover we have during wet springs is the second step. Thankfully, although clovers can and do naturalize here, they rarely make up a large portion of the forage in a pasture. Lastly, applying cultural and chemical control methods if they do become excessive will keep them in check. Avoiding overgrazing of pasture grasses will help keep clovers and broadleaf weeds from becoming excessive. Your local county extension office can help with clover management as well as other equine related questions.