Hello Abbie,

Alsike clover can cause photosensitivity and can also harbour a toxic fungus which can produce liver damage. Here is what the Merck Veterinary Manual has to say about liver dysfunction and alsike clover:

"Alsike clover poisoning may be fatal with progressive loss of condition and signs of hepatic failure and neurologic disturbances. Colic, diarrhea, and other signs of GI disturbances have been noted. Affected hoses may be markedly depressed or excited. Prolonged exposure is usually required before signs of hepatic insufficiency are evident. Serum chemistry alterations include increased GGT and AST activities, and hyperbilirubinemia, with direct bilirubin frequently being ≥25% of the total."

So, I recommend that you have your horse's blood checked for liver enzyme activity to determine if his liver has been affected.

Chlorophyll metabolism may also be a factor, and could explain why your other horses are not affected. All green plants contain chlorophyll. And, the bacteria in the hind gut break it down to phylloerythrin. This substance is then absorbed into the bloodstream and is processed by the liver and excreted in the bile. However, the liver in some horses (a genetic condition) cannot metabolize phylloerythrin, so this substance leaves the liver and ends up back in the bloodstream. It is carried to the surface of the skin, where is produces photosensitivity.

Alfalfa contains a large amount of chlorphyll, so this should be avoided. Also, if you are allowing fresh pasture-grazing, you may need to switch to feeding a hay diet.

I would certainly keep the immune system and liver function is top shape, so make sure you're filling in nutritional gaps with a good vitamin/mineral supplement that is high in the B vitamins and omega 3 fatty acids, such as Glanzen or Glanzen Complete.

Blue Green Algae is also very beneficial, so take a look at a palatable version, called Spirulina Wafers.

I hope this is helpful. Please keep me posted.

All the best,

Dr. Getty

Where are you from? Bayfield, CO