As a feature, our Tribute® Superior Equine Nutrition main product line now has no added iron. Some people are saying “finally!”, while others are asking if iron is bad. So, what is the deal with iron in horse feed?
 

The short answer is that iron is not bad. In fact, it is a required nutrient! The long answer is that there are many misconceptions about iron in horse feed and how it impacts the horse and we will briefly cover several in this article.

First, there is no such thing as an iron-free horse feed. Iron is a mineral that is ubiquitous, meaning it is found everywhere and as plants grow, they incorporate iron. Most of the iron in horse feed comes from background iron that is contained in the base ingredients. Iron is not a nutrient that is required to be listed on a label, so do not assume a feed is iron-free if you do not see iron on the guaranteed analysis.

Supplemental iron has traditionally been added to horse feeds because iron is a required nutrient and an iron deficiency results in anemia. In the not too distant past, anemia from large parasite burdens or severe cases of undiagnosed ulcers were relatively common issues in horses. As our knowledge of horse health and access to diagnostics and treatments have improved, these issues have been largely eliminated and the need for supplemental iron has decreased. In other cases, feed manufacturers may be using iron as a way to color feed to make variations between batches less apparent.  

A common concern is that iron in the horse’s diet, whether from the hay, feed or water, will cause secondary copper and zinc deficiencies and result in issues, such as poor hoof quality. This is a valid concern because iron does compete with copper and zinc absorption in the small intestine. Because of this, some people look for very specific ratios of iron to other minerals in the diet or add supplemental copper and zinc. The problem with this approach is that the validity of these ratios and their impact on the horse have never been tested in a controlled trial. These ratios are simply based on the minimum daily requirement for each mineral, derived from the Nutrient Requirements of Horses (2007) publication. There are a number of problems with this approach. Since we know there is often high background iron in the horse’s diet and it will fluctuate with changing forage sources, we choose not to focus on an undefined ratio that is not research proven, but rather on ensuring we meet the copper and zinc requirements of the horse, regardless of how much background iron is in the diet. To do this, we utilize specific organic trace minerals that are research proven to use an alternate absorption mechanism. Simply put, this allows us to circumvent the competition with iron in the small intestine and ensure that horses’ copper and zinc requirements are met.

Many horse owners are also concerned with iron causing metabolic disorders; however, the information floating around the internet misinterprets the relationship between iron (specifically serum ferritin) and metabolic status. Serum ferritin has been found to be a marker of insulin resistance in humans; however, research has also shown that dietary intake of iron does not affect the risk of development of insulin resistance in humans. Rather, serum ferritin is high as a byproduct of the disease process. The popular press articles that are cautioning against dietary iron in horses are based on a single study completed at Michigan State University, published in 2012, that found high serum ferritin in horses with insulin resistance. This study DID NOT look at the impact of varying levels of dietary iron on serum ferritin status. There was NOT a nutrition component to this study. This study simply confirms what we know from human models, which is that serum ferritin levels are a marker of insulin resistance in horses.

To date, there is no evidence that dietary iron impacts metabolic status in horses. We do know that equine obesity and diets high in sugar and starch both contribute to increased risk of metabolic disorders in horses.   

The iron levels in our Tribute® Superior Equine Nutrition products are not harmful in any way to your horse. We’ve chosen not to add supplemental iron to the majority of Tribute® Superior Equine Nutrition feeds, as horses in most circumstances will receive more than their daily iron requirement from the iron in their hay and the naturally occurring iron in the feed ingredients. The exception to this is horses in intense levels of work, namely racehorses, who may require additional iron to support the demands of their heavy work load. Our line of race feeds maintains supplemental iron from bioavailable sources in order to meet these horses' unique needs.

If you have questions about this or any other nutrition-related topic, please reach out to our friendly and knowledgeable Equine Specialists here. We are happy to answer any questions or help you develop a personalized equine nutrition plan for each of your horses!
 

Nicole Rambo, Ph.D.