Some exciting research has just been published! On the topic of muscles and mind, magnesium (Mg) is ‘hot’.
Anecdotal reports on the benefits of oral Mg are numerous — with many owners and vets describing reduced skin sensitivity, ‘hot’ behaviour, tying-up, irritability, muscular cramping, weakness, insulin-resistance, cresty necks and stiffness — when horses receive a Mg supplement. The possibility that a natural oral supplement might be useful, is very attractive – and recently, some great research has confirmed the anecdotes and observations.
One study conducted in Australia compared an oral Mg supplement to the sedative acetylpromazine (ACE). The ‘reaction speed test’ measures the time taken for a horse to cover 2 metres in a custom-built chute, after being startled. Before the test, the horses travelled at 5.3m/sec, after receiving ACE they reduced their speed to 3.5m/sec – and when they were supplemented with 10g of Mg per day for 7 days, their speed reduced even more, to 3.1m/sec – i.e. they were less reactive than the ACE-sedated horses! This is the first time an objective measurement of behavioural change due to oral Mg supplementation has been reported in the horse. But, as scientists we like to see consistency and repeatability – which another new study has provided.
Published in 2017, this study measured heart rates and cortisol (the ‘stress’ hormone) when horses were loaded onto a weighbridge for 3 seconds. Heart rate was significantly lower when the horses received ACE or Mg, compared to when they were unsupplemented. The veterinarians from the University of Guelph who undertook the studies weren’t surprised to see the Mg have a similar effect to ACE. The link between low Mg and anxiety has been well-established and supplementing Mg reduces stress in several species, including humans and rodents.
The primary active in the study was Mg, with supporting bioactivity from thiamine. Mg is required for conversion of thiamine into its active form and a Mg deficiency could potentially induce a secondary thiamine deficiency. That thiamine has a calming effect was described in racehorses over 50 years ago. In 1961, researchers noted that: ‘…on three occasions after thiamine had been administered the horses were less excitable while walking to the racecourse. This was observed also by the jockey and the trainer, neither of whom knew the identity of the injections being administered …’. Studies in rats also demonstrate a thiamine-induced reduction in biomarkers of anxiety, and that a combination of Mg and thiamine reduces post-natal depression in mice! In the Canadian equine study, when given 30 minutes before the onset of a stress, Mg-thiamine is as effective as ACE in blunting stress-induced increases in heart rate.
Mg is also thought to help soothe nervous horses by working in concert with calcium on muscle contractions. Calcium stimulates contraction, Mg relaxation. If Mg levels are low, muscles can spasm due to an inability to achieve full relaxation. Although the presence of low Mg in the muscle tissue may stem from a genetic disorder rather than dietary intake, many horses have responded to Mg supplementation for treatment of chronic tying-up. International Olympic veterinarians found Mg reduced muscle tiredness and increased work tolerance in show jumping, 3-day event, dressage and 4-in-hand horses. They also reported a decrease in skin sensitivity, ‘hot’ attitudes, unexplained hindleg lameness (muscular in origin), tying-up, irritability and muscular cramping, weakness and stiffness, particularly of the hindlimbs. Providing supplemental Mg alleviated signs and symptoms of deficiency – improving behaviour and performance.
Another recent study found that a daily magnesium supplement at clinically recommended intake had an effect on muscle function - with lower muscle enzyme levels after exercise, and also lower heart rates. And because Mg is a catalyst for generating energy (ATP – the basic currency of energy), and facilitates oxygen delivery and uptake in working muscles, correct Mg intake helps sustain the high oxygen consumption required for optimum muscle function and performance.
Other veterinary conditions in which Mg is involved include insulin resistance (IR) and Equine Metabolic Syndrome (EMS), synchronous diaphragmatic flutter (SDF) in endurance, event and racehorses, developmental bone and growth disorders in young horses, and tetany (grass and transit). However, one veterinary condition in which Mg is not involved is ‘bighead’. There is no evidence that Mg has a role in nutritional secondary hyperparathyroidism (bighead) - in fact numerous studies have confirmed that oxalates have no effect on magnesium status in horses. Species is important here — while Mg deficiency has been implicated in oxalate toxicoses in ruminants such as cows and sheep, the opposite is true for horses.
We're excited to be releasing our new product this month - EzyMAG+ for Muscles and Mind. For more information visit our product page. Download brochure.
EQUINE CLINICAL NUTRITION
By Dr Jennifer Stewart