Question from the vet: Why Magnesium Oxide?

We always consult our panel of veterinarians when formulating new products, but we also often get questions from veterinarians about the properties, composition and effectiveness of the products. One of the questions is:

Why do you use magnesium oxide?

We use magnesium oxide because it is a natural type of magnesium and the most effective in terms of absorption in horses.

It ionizes calcium and magnesium seamlessly for absorption in the small intestine, as horses have plenty of stomach acid.

Justification

Magnesium has over 300 functions in mammals. Of particular interest to horses is balancing other macrominerals and protecting against endotoxins from, for example, “gut events” such as fermentation errors that can cause colic and lameness.

Magnesium has countless roles in energy/sugar metabolism, including in the transport of sugar into the cells, for combustion, energy formation/ATP, as well as in neuromuscular functions in relation to the function of the important signaling substance, acetylcholine.

The need is higher during growth, sweating/heavy physical activity and when there is a risk of inflammation. Therefore, the content in Regulator Complete's products is at the high end, (also in relation to magnesium) with amounts that ensure optimal levels and ensure that the horse has surplus to gain, in relation to various biological requirements.

Magnesium supplements in the feed are available in many forms, of which magnesium oxide is naturally occurring and contains as much as 60% magnesium, which provides good absorption and retention in the body.

Magnesium citrate is not naturally occurring (it has to be manufactured) and contains a much smaller proportion of magnesium, only 11-16%. This means that 4 times more would have to be added to achieve a given level.

In monogastric animals, there is no significant difference in the absorption of different types of magnesium, as the absorption is approximately 50% and the retention in the body is 34% for both magnesium oxide and citrate, but as mentioned, approximately 4 times more magnesium citrate must be given to achieve the desired amount.

In human nutrition, there are some opinions, not relevant to horses, about the absorbability of some forms of citrates, which are stated to be better than other forms (typically 30% vs. 4%, but this is based on calcium, not magnesium). This is especially true for older people who have a lack of stomach acid. It is not well documented, because citrates can form unabsorbable “soap compounds” if there is difficulty digesting fat in humans and because the other forms are well absorbed when taken with meals. Finally, magnesium has better absorption than calcium (45-50% vs. 25-30%). This is quite general.

Conclusion

The humane considerations are not relevant to horses, as horses generally have abundant stomach acid, meaning that horses easily ionize calcium and magnesium for absorption in the small intestine. There is no reason to use a non-naturally occurring form of magnesium in horse feed, especially when they are less effective.

Read more about magnesium here: 100% is not enough

If you have any questions about magnesium, you are more than welcome to use the comments field so that others can also benefit from the answer.

Scientific sources

1. Magnesium as an Equine Dietary Supplement - Metabolic Disorders - MSD Veterinary Manual (msdvetmanual.com)
2. The Importance of Magnesium in Horse Diets - Kentucky Equine Research (ker.com)
3. Magnesium for Horses: Which Form is Best? (feedxl.com)
4. The Importance of Magnesium for Horses (agsolutions.com.au)