If you have ever dealt with a nervous, spooky or tense horse, you have probably considered a calming supplement. The market is full of options. herbal blends, tryptophan pastes, valerian tinctures. But increasingly, riders and vets are turning to magnesium as a first-line approach. Horse Tonic's ZEN is built entirely around this mineral. Here is what you need to know.
What is ZEN?
ZEN is a liquid calming supplement made in Belgium by Horse Tonic. Its formula is simple: magnesium chloride for rapid absorption and magnesium citrate for sustained release. No herbs, no valerian, no tryptophan. Just magnesium in the two forms that are most bioavailable to horses.
How magnesium affects horse behaviour
Magnesium plays a central role in neuromuscular function. It regulates the release of stress hormones, supports GABA receptors (the brain's natural calming mechanism), and helps muscles relax after contraction. When a horse is magnesium-deficient, the nervous system becomes hyperexcitable. This shows up as spookiness, tension, muscle twitching, difficulty focusing, and overreaction to routine stimuli like sounds or movement.
Performance horses are particularly prone to deficiency. Hard training, sweating, travel stress and competition pressure all deplete magnesium faster than a standard diet can replenish it. Grass and hay in Northern Europe often contain lower magnesium levels than horses need, especially on sandy soils.
Signs your horse may be magnesium-deficient
Watch for these behaviours: excessive spookiness or startle responses, muscle tightness or cramping (especially in the back and hindquarters), difficulty standing still or relaxing, teeth grinding, tail swishing unrelated to flies, and a general sense of being "wired" even when the environment is calm. These signs do not guarantee a deficiency. a blood test is the only way to be sure. but they are strong indicators.
How to use ZEN
ZEN is administered orally at 30ml per day for maintenance. For acute situations (competition day, transport, vet visits), the dose can be increased to 60ml given 2-4 hours before the event. Because ZEN is liquid, it absorbs faster than powder alternatives. which matters when you need results the same day.
For best results, Horse Tonic recommends a loading phase of 2-3 weeks at the standard dose before expecting consistent behavioural changes. Magnesium works by restoring depleted stores, not by sedating the horse, so the effect builds gradually.
Is ZEN safe for competition?
Yes. Every batch of ZEN is independently tested by an accredited OMCL laboratory for all FEI-prohibited substances. Unlike valerian-based products (which are banned under FEI rules), ZEN contains only magnesium. a mineral, not a drug. You can use it freely at any FEI-regulated event.
The bottom line
Magnesium deficiency is common in sport horses, and supplementation genuinely helps. ZEN is a clean, liquid, FEI-safe formula that addresses the root cause of nervousness rather than masking it with sedation. If your horse is tense, spooky or hard to settle, magnesium is worth trying before reaching for stronger interventions.