Do you think your horse may be deficient in Magnesium?
Lets start at the beginning. Magnesium along with calcium and phosphorus are known as the major minerals. Major meaning, they require more than micro or trace minerals (copper, zinc etc). Magnesium makes up approximately 0.05% of the body mass and the skeleton stores sixty percent of body magnesium and about 30 percent can be found in muscle. Magnesium is absorbed from the small intestine in the horse, with very little thought to be absorbed from the large intestine. As a general rule magnesium can be either too low and/or the calcium to magnesium ratio can be too high, in forage alone. Whichever one applies, the diet won’t be optimal.
Adequate magnesium is needed in a horses diet so it can:
- Work closely with calcium to maintain proper muscle function. When muscles receive nerve signals telling them to contract, calcium is released from special compartments within cells and moves onto muscle fibres causing them to contract. Magnesium stops the contraction by pushing calcium back into these compartments.
- Enable muscle relaxation, it can support recovery and help to ease muscle pain and cramping in animals following heavy work.
- Support athletic performance by enhancing oxygen delivery to muscles, and promoting muscle strength and metabolic processes that result in protein synthesis.
- Help nerve cells transmit signals to each other and to muscles by regulating ion balance across cell membranes.
- Helps a calming effect, helping to ease muscle tremors and nervousness.
- Improve tolerance to stress and resistance to illness and injury. Stress causes magnesium to be depleted in the body faster. Ensuring optimal magnesium levels can help speed up return to homeostasis following exposure to an external stresses.
- Contribute to normal fat distribution in horses by minimizing cresty necks or fatty pockets.
- Magnesium helps cells respond to insulin.
- Help horses with endotoxemia, bacterial toxins in the blood, which can lead to laminitis in horses. Horses with endotoxemia are often found to have low levels of this mineral in their blood.
- Help with calcium mobilization. This can support healthy bones and overall well-being in your horse.
The symptoms of a magnesium deficiency are the same as for excessive ionised calcium in relation to magnesium levels. Mild to moderate deficiency can occur in horses and may affect their mood and performance. Horses that do not get adequate amounts of magnesium from their diet might only show signs of deficiency during stress or competition. Most signs of magnesium deficiency are related to disordered neural or muscular function including - Nervousness/Excitability/Anxiety, Unable to relax or focus, Muscle tremors, spasm, twitching, flinching skin, trembling, Muscle pain or cramps, Not tolerant of long periods of work, Highly sensitive to sound or movement, Hypersensitive skin, Irritable moods, Resistance to training, Fatigue, Irregular heartbeat, Teeth grinding, intestinal symptoms, Increased perspiration and anhidrosis. In more serious cases, the following rare symptoms may be observed: Chronic Tying Up, especially tight & sore backs, Irregular heartbeat, Increased respiratory rate or laboured breathing, Metabolic dysfunction, abnormal fat distribution and weight gain, Muscle convulsions, gait disturbances, including stilted gait, base wide gait behind, difficulty controlling the hind end when turning and reluctance or inability to canter.
Most forage and especially quick active growing grass are low in magnesium. Such grass is also likely low in sodium and high in potassium which can exacerbate a deficiency. High potassium can slow the absorption of magnesium. Sodium typically enhances absorption but is low in these circumstances (needing supplementation). Excessive fat levels can also disrupt absorption of Magnesium ie: high volumes of oil.
The best way to find out if your horse is likely to be magnesium deficient is to analyse the diet. A blood test is not a reliable way to check blood magnesium levels as the horse works to keep blood at homestasis levels and will draw on skeletal, organs and soft tissue to maintain this. A normal blood range also doesn't show if the rest of the body (organs, soft tissue, muscles, skeletal) is lacking.
According to the National Research Council (NRC) , the daily requirement for horses is estimated at 15 mg per kg of body weight. For a 500 kg horse at maintenance, the magnesium requirement would be 7.5 g per day. This is based on the minimum supplementation level to prevent deficiency symptoms. Dr Eleanor Kellon (USA expert in nutritional needs and balancing equine diets) recommends at least 150% of NRC levels for mineral balancing to allow a margin of error. Meaning a 500kg horse at maintenance daily requires 11.25g. This will keep them above a deficient level. A 500kg horse in light work requires 14.25g and in heavy work 22.5g!
Rather than feeding your horse more magnesium in isolation, it is important to look at their diet as a whole. We do not recommend excessive supplementation of magnesium in horses – more is not better. Some excess magnesium is excreted but levels in the kidney and bone will rise. Excess may lead to depressed calcium and phosphorus uptake, intestinal, renal and heart issues. In general, it is more important to maintain a proper calcium-to-magnesium ratio than to be concerned about providing excess magnesium. The two minerals are ideally kept within a ratio of 2.5:1 to 3:1, calcium to magnesium with the optimum target ratio being 2:1. This commonly shows up in a diet that is heavy on lucerne. Lucerne is a fantastic highly absorbable food form of calcium. Excess calcium has the same symptoms as excess magnesium leading people to think lucerne is the issue. When in majority of cases once the magnesium to calcium ratio is corrected, Lucerne can be part of a successful feeding program. (The same applies to the high levels of Potassium in Lucerne - once Sodium is balanced). This is where feed programs such as Feed XL fall short as they do not consider the ratio balances.
Some forms of magnesium are less concentrated meaning you need to feed larger amounts to provide the same amount of mineral. Some taste better than others. Magnesium Oxide is a very popular option to reach for. Magnesium oxide is made via a process of calcination where a source of magnesium like magnesite or magnesium carbonate is burned at very high temperatures to produce magnesium oxide. But buyer beware, it varies in quality. Magnesium Oxide is commonly very high in Iron, and heavy metal contamination can be an issue. Be sure to buy a premium grade of magnesium oxide with a tested lab analysis of a high level of magnesium and very low level of iron. That cheap 20kg bag of "cow" magnesium oxide might not be the best option for your horse. This also possibly explains the price difference between "cow" and "horse" mag oxide. Always good to ask to see the analysis/testing results to confirm as that may not always be the case. Heavy metal contamination is a serious concern for horses with a typical much longer lifespan than cows, meaning more exposure and collection of toxins (chemicals, pesticides, insecticides, natural toxins etc). Our aim is to also reduce added iron to the diet - that includes ingredients or nutrients with high levels of iron such as zeolite.
There is much confusion and controversy throughout the industry as to absorption levels of magnesium. Each company has its own interpretation and there are no actual studies on absorption rates specific to equines. A 2005 study on rats, determined that Magnesium Gluconate had the highest absorption rate of 57% and Magnesium Oxide 48%. (Proteinate did not feature in this study - see below). However Magnesium Gluconate contains just 5.3% of actual magnesium - meaning to get 10g of Magnesium you would need to feed 186g, whilst you would need to feed 17g of MgO to provide 10g Magnesium. Another source states Magnesium Oxide had a low absorption rate of just 9%.
Here at HHIO, after exstensive field trials before we launched in 2018, we use Magnesium Proteinate. It is claimed that it has an absorption rate of 80%, however that has not been able to be verified. It is an organic form of magnesium that are bound to amino acids and a range of peptides. They are easily absorbed and readily metabolized. It was the best balance of cost, taste and volume vs performance of desired results that we discovered. We specifically observed a softening and reduction of neck crests compared to other forms of magnesium used (Magnesium Oxide and Magnesium Aspartate) and the amount needed to be fed to relieve 'deficieny' symptoms was low.
Take away message - Magnesium is an important mineral in a horses diet. Optimum Magnesium levels will not be provided for in forage alone. Magnesium works in balance with Calcium - one out of balance with the other creates issues. More magnesium is not always better. Excess calcium can be mistaken for magnesium deficiency. Symptoms are a more accurate measure to go by in regards to Magnesium status in the body, than by blood tests. Not all magnesium sources are created equal.
For those interested in correct magnesium supplementation in humans, check out Morley Robins Root Cause Protocol at https://therootcauseprotocol.com/. Leaders in reversing inflammation in human health by correct mineral balancing namely magnesium and copper.