I’m concerned about the amount of iodine that seaweed contains. I have been feeding seaweed to my horse as a supplement because I was told it was good for her hooves and her gut, but I’ve read that it contains very high levels of iodine, way over the couple of mg a horse needs per day. I was told that iodine can be toxic in high levels and now I’m worried that I’m feeding toxic levels of iodine.

You are correct that seaweed contains high levels of iodine, but if you feed seaweed from a reputable manufacturer and follow the feeding directions, you will not be feeding toxic levels of iodine. Maximum tolerable levels of iodine are about 50 mg daily for a 500 kg horse, after which the horse could suffer toxic effects.

Seaweed is a rich natural source of minerals and contains beneficial polysaccharides not found in land vegetables.
Seaweed is a rich natural source of minerals and contains beneficial polysaccharides not found in land vegetables.

From a seaweed product that contains 500 mg of iodine per kg, and which is fed at a daily rate of 30 g, your horse will receive 15 mg of iodine, well within the maximum tolerable level of 50 mg per day (based on a 500 kg horse). Pregnant mares have a lower maximum tolerable level, and ideally should not be fed more than 10 mg of iodine daily (based on a 500 kg mare).

Horses require as a minimum, up to 3 mg of iodine per day (based on a 500 kg horse) depending on their workload. Many nutrients are supplied naturally in the diet in much higher quantities than the horse requires, but their bodies are able to extract what they require and/or excrete or otherwise deal with the excesses. In fact it is unusual for a horse to take in just the ‘right’ amount of many of the vitamins and minerals!

Seaweed is fed to horses for a variety of reasons, including to boost coat and hoof health and shine.
Seaweed is fed to horses for a variety of reasons, including to boost coat and hoof health and shine.

Seaweed provides a wide range of benefits to the horse and is reputed to strengthen hooves and improve haircoat, have a beneficial effect on the gut (probably due to its polysaccharide content), support good immune function and help with weight loss. It’s the richest vegetable source of minerals for horses. The range of benefits seaweed provides is worth the high level of iodine it supplies and it’s possible that some horses respond positively to the high level of iodine.

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About Clare MacLeod

Clare MacLeod MSc RNutr is one of the UK’s few registered independent equine nutritionists who also has expertise in health and fitness. She advises private and commercial clients in all sectors of the horse world and is a hands-on horse owner herself. Clare is passionate about correct nutrition as a foundation for good health, without which peak fitness is not possible. She states “Good nutrition isn’t everything, but there’s nothing without it”.
  • OceanFeed

    Ocean Harvest Technology agrees with what Pegus have stated in relation to the high levels of iodine found in seaweed being given to horses . The common seaweed that is for sale either in bucket or bag form use kelp (Laminariales) and Ascophyllum (Fucalus) specific families of seaweeds that may contain as much as 1,850 ppm iodine (Kraan 2013). Unfortunately, people have a tendency to classify all seaweeds as kelp just as the layman might consider every breed of horse a Thoroughbred. There are numerous other specific seaweeds, including species of the Palmariaceae, Gigartinaceae, Bangiaceae, and Ulvaceae that contain a fraction of the iodine compared to kelp. That is the reason why Ocean Harvest Technology has developed a seaweed product called OceanFeed EquineTM. OceanFeed
    EquineTM contains eight specific types of seaweed without using Ascophyllum or Kelp. OceanFeed EquineTM has < 250 ppm or up to 19% less iodine that is found in other products. That works out at 11.25mg of iodine giving a 500kg horse 45grams of OceanFeed EquineTM per day. OceanHarvest Technology has done a lot of research in developing OceanFeed EquineTM OceanFeed EquineTM has been tested at the Irish Equine Centre. One of the findings was that there was an improvement in the differential white cell count meaning the immune system is stimulated. Furthermore liver function improved reducing heavy metals in the system . A total of twenty six analysis were done for prohibitive susbstances all of which came back negative. A copy of this report can be got on request. OceanFeed EquineTM is also Nops accredited. OceanFeed EquineTM comes in pellet form which makes it more palatable and insures its dust free.