Most of us know the fabulous books, movies and television series on the life of James Herriot - the British veterinarian who wrote about his experiences as a vet in Yorkshire. I’m fortunate to work in India with a Professor from Michigan who worked with James Herriot and has many first-hand stories of life as a country vet in Herriot’s practice. As I was reading about recent research into the effects on equine behaviour of a magnesium-thiamine combination, the Herriot books sprang to mind….if only they could talk.
Our efforts to understand our horse’s feelings would be so much easier if they could tell us about them – or if we become better at ‘reading’ their body language. Traditional assessments of emotional states, although useful sometimes, are not always straight-forward or easy to perform. Take the ‘fear test’ for example – where a horse’s fear reaction is tested by surprising them! Items required include a colourful umbrella, a tarpaulin with a bucket of feed in the middle, a stop watch and a plastic motorised duck that every 20 seconds rotates and makes a noise.
Fear-related reactions prepare the horse to deal with danger and oral magnesium (Mg) is heavily promoted as a calmative. Certainly, anecdotal reports on the benefits 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. Most of these reports have not been scientifically validated, but recently some great research has confirmed the anecdotes and observations.
Conducted in Australia, a recently-published study compared the effects of Mg and acetylpromazine (ACE) in horses undertaking a reaction speed test, ie the time taken for a horse to cover 2 m 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. When they received 10g of Mg per day for 7 days, their speed reduced even more, to 3.1m/sec – ie 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 we like consistency and repeatability – which another new study has provided. Canadian university research published in 2017 looked at the amount of stress horses experienced performing a set task when they received either ACE or a Mg supplement, compared to when they were unsupplemented. The horses were loaded onto a weighbridge for 3 seconds. Heart rate and cortisone were significantly lower when the horses received ACE or the bioactive combination of Mg + thiamine 30 minutes before the onset of a stress. In addition, the paradoxical adverse effects of ACE found in some horses (tachycardia, penile prolapse and hypotension), have not been reported with Mg + thiamine. Mg is required for conversion of thiamine into its active form and a Mg deficiency could potentially induce a secondary thiamine deficiency.
A thiamine-mediated tranquilising effect and slowing of heart rate were described in racehorses over 50 years ago in 1961. The 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….’. Studies in rats also demonstrate a thiamine-induced reduction in biomarkers of anxiety, and a combination of Mg and thiamine reduced post-natal depression in mice!
Mg is also thought to help soothe nervous horses by working in concert with calcium on muscle contractions. 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 and improved behaviour and performance.
Although behaviour can be challenging to measure, some responses to Mg can be measured in heart rate responses and blood tests. A daily Mg supplement reduced heart rates and muscle enzyme levels after exercise in horses that tie-up or have PSSM. Other veterinary conditions in which Mg is involved in the cause, management, treatment and prevention, include insulin resistance (IR); 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). Adding supplementary Mg to the daily diet is intended to address subclinical deficiencies, which although difficult to diagnose, produce recognisable clinical signs and syndromes.
Blood tests have also shown excellent responses in pregnant mares, foals and older horses when therapeutic levels of vitamin E are fed daily, with improved foal immunity, colostrum IgG levels, vaccination responses and the killing ability of white blood cells.
Jenquine’s EzyMag+ contains the therapeutic levels of Mg, thiamine and vitamin E that have been shown in research and clinical trials to be effective.Extreme Mg deficiency is life-threatening and rarely seen in horses – unless they are critically ill. However, additional dietary Mg, thiamine and vitamin E are required for growth, work, late pregnancy and lactation and during moderate to intense work, when total daily requirements are over twice maintenance levels.
The remarkable Pat Parelli developed the chart for classifying temperament, while others have proposed a relationship between hair whorls and temperament – suggesting that whorls located below the centre of the eyes predict a calm temperament; those high on the forehead suggest a flighty temperament; whorls on either the left or right side of the head indicate handedness, and according to the research, the side in which the hair whorl is on, is the side that is hardest shoe!
If you’re interested in learning more on behaviour, here’s a couple more recent interesting reads. The first link being Episode 8 from our Equine Clinical Nutrition Series which focuses on EzyMAG+.
Equine Clinical Nutrition
Dr Jennifer Stewart