Iodine Deficiency in Horses 

Iodine is a trace mineral that horses uses to regulate their basal or resting metabolism. Iodine is concentrated in the thyroid gland, located next to the trachea and behind the larynx. It is essential to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which regulate the horse’s metabolism. 

Symptoms of Iodine Deficiency in horses: 

Foals, as well as horses under two years of age, are more prone to Iodine deficiency. Foals born from a mare with an iodine deficiency often have a high mortality rate and are more likely to develop joint and bone abnormalities. 

Some symptoms of Iodine deficiency in horses include: 

  •  Goiter / Swelling of the thyroid 
  • Dry and dull haircoat 
  • Lethargy 
  • Hair loss 
  • Decreased growth and bone calcification 
  • Thickened skin 
  • Lack of appetite 
  • Low body temperature 
  • Cold intolerance 

 Note: Deficient foals can be stillborn or born weak, have hypothermia, difficulty standing, and a poor suckle response. 

 Sources of Iodine: 

While horses only require Iodine in very small amounts, there is often little information available regarding iodine concentration in common forages, as Iodine is not usually measured in a hay sample analyses. For horses consuming forage-only diets, a trace-mineralised salt block with iodine such as Ranvet’s Salt Lick is an easy way to encourage enough Iodine consumption.  

A concentrated vitamin-mineral supplement such as Ranvet’s Ration Balancer is also an option and could be added to your horse’s diet if supplementation is necessary. Pre-mix feeds and commercial grain concentrates often contain enough amounts of iodine to meet your horse’s needs.  

Note: Iodine toxicity can occur with over-supplementation. Iodine toxicity can cause hypothyroidism; a condition which affects thyroid function and hormone production resulting in goiter, obesity, poor coat condition, lethargy, and intolerance to cold. 

If you are unsure about the iodine levels in your horses’ diet, simply complete our online diet evaluation service where we can analyse your horses daily ration and determine if their iodine levels are correct.  

Complete the online form here



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Every product in the Ranvet range has been developed to meet a horse’s most specific need at any given time, be it in a training environment or on a breeding farm. Having pioneered the formulation of specific medications and dietary supplements for horses, the company is now recognised as a leader in the areas of equine health and nutrition.

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