Kelp is a species of seaweed that is a nutritionally-dense source of protein and trace minerals. It contains the essential mineral iodine, which is important for thyroid function, growth and metabolism.

Horses with digestive health issues, low appetite, poor tolerance to cold weather or a dull, dry coat may benefit from kelp supplementation.

Kelp also contains prebiotics that promote a healthy gut microbiome. It is sometimes fed to horses with diarrhea and leaky gut.

This nutritional seaweed has also been shown to benefit horses with gastric ulcers by promoting the production of compounds that protect the stomach lining.

Kelp meal is safe for horses, but it should not be over-supplemented. Chronically high intake of iodine can affect thyroid function.

Kelp for Horses

Seaweed has been consumed by humans for thousands of years. There are over 1,700 different species of seaweed, divided into three major groups: green, red and brown seaweeds.

Kelp is a type of brown seaweed of the genus Laminaria. It is naturally found in cold ocean waters and can be grown in controlled environments. [2]

This is the type of seaweed most commonly fed to horses and other livestock. Kelp grows along coastlines and is naturally grazed by many herbivorous animals, including sheep and cattle in Scotland, Iceland, Norway, and Scandinavia.

Feral horses located near large bodies of water consume kelp, particularly during snowy weather when pasture is less accessible.

Kelp has also been fed to horses since the Roman period as a vitamin and mineral supplement. It is typically fed in a dried, powdered form to domesticated horses. [3]

Iodine content

Kelp is used a nutritional supplement because of its high iodine content. While this seaweed is a source of many trace minerals, iodine is the most abundant mineral.

Iodine levels vary by seaweed species, age at harvest, and the harvesting and drying method used.

In one study, iodine content was measured in seven samples of laminaria seaweed harvested in Maine, British Columbia and Washington. Levels of this trace mineral ranged between 796 to 2984 mg per kg. [2]

Because kelp is such a concentrated source of iodine, over-supplementation could result in iodine toxicity. Always follow manufacturer feeding guidelines closely.

If you are adding kelp to your horse’s diet, we recommend using commercial supplements that provide a standardized amount of iodine per serving. Reputable supplement manufacturers should perform quality control analysis to verify the levels of minerals in the product.

Additional Nutrients

Kelp is also a source of other nutrients including essential minerals, amino acids and fatty acids. It contains two limiting amino acids – lysine and methionine – that are commonly lacking in the horse’s diet.

Kelp has relatively low fat content, but it does contain the omega-3 fat eicosapentaenoic acid (EPA), which has anti-inflammatory benefits. [1]

Below are the other macrominerals and trace minerals that are most abundant in this genus of seaweed: [1]

Kelp meal is typically fed to horses in relatively low amounts and is unlikely to meet dietary requirements for the minerals listed above. It is recommended to feed kelp alongside a balanced equine vitamin and mineral supplement.

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How to Feed Kelp to Horses

Horses are typically fed kelp at a rate of 5 – 20 grams per day, depending on iodine needs and the concentration of the product used.

A 5 gram serving of kelp meal will yield between 3.5 to 15 mg of iodine. [1] This is adequate to meet the minimum iodine requirement for a mature horse at maintenance of 3.5 to 4 mg per day. [16]

Because both iodine deficiency and toxicity pose a health concern for horses, care should be taken to measure serving sizes carefully and to feed based on instructions from the manufacturer or your nutritionist.

A nutritionist can help you calculate how much iodine is in your horse’s diet and how that compares to individual requirements. Commercial feeds often include iodine in the form of calcium iodate or ethylenediamine dihydriodide (EDDI).

You can submit your horse’s diet for analysis to determine whether your horse is meeting their iodine requirement.

Generally, it is recommended to use kelp in the form of a finished supplement product rather than feeding kelp on its own. This will reduce the risk of over-supplementation and possible adverse effects.

Kelp Benefits for Gut Health

In addition to its use as a nutritional supplement, Kelp is also fed to horses to support gut health and the m