Can someone turn on the light?

The horse’s eyes function differently from our human eyes. For example, a horse needs more time to acclimate its eyes to a transition from light to dark and vice versa than a human. That is why many horses find it quite challenging to go into a dark trailer out of the bright sunlight, which regularly creates dangerous situations. Researchers at a French university wondered how horses would react to various LED lights in the trailer. And especially if there would be a difference in how easy they were to load and transport.


For the study, they used 22 French Trotters, 2 or 3 years old, who were trained for the trotting track and who had only been transported as a foal alongside their mothers in an open trailer once. This study was therefore their first experience with a standard two-horse trailer. In that trailer, the scientists used different types of LED lights. The lights were arranged in such a way that they did not cast shadows or cause dark spots. Each horse was loaded into the trailer three times at 20 day intervals under different lighting conditions.

Loading was done in the most common way at this time: putting pressure on the halter and releasing the pressure when the horse moves forwards. If necessary, the handler was assisted by a second person who waved his arms behind the horse until it moved forward. This is similar to the way we load horses at

Five different lighting conditions were tested:

  • Natural daylight (so no lights in the trailer);
  • LED light with a heat of 4500 K (an average light colour) at 100% emitted power;
  • LED light with a heat of 4500 K at 50% emitted power;
  • LED light with a heat of 6300 K (more bluish light) at 100% emitted power;
  • LED light with a heat of 2700 K (more yellowish light) at 100% emitted power.


The results were very interesting. When the trailer was illuminated with LED lights with a heat of 4500 K at 50% emitted power, the horses showed the lowest heart rate and the least negative behaviour. The researchers also discovered that if the light in the trailer was stronger than the natural light outside and had a light intensity above 4500 lx, the horses clearly needed less time to load. They clearly showed fewer stress signals.

The scientists then looked at how the horses reacted to the different types of light while in the trailer. It was found that their heart rate dropped the quickest after loading if the light heat was adjusted to one of the two extremes: either more yellowish (2700 K) or more bluish light (6300 K). This would mean that if trailers were equipped with adjustable LED lights, the horses would relax more quickly and experience less stress during the ride. All the horse owner would have to do is change the light colour with a remote control once the horse has been loaded.

Of course, the light in the trailer is just one of the factors that determine the level of tension a horse experiences during loading and transport. For example, horses may have had a bad experience in or around the trailer. Or the way of loading gives them a lot of stress. And there are also many horses who find it difficult to be away from other horses. In such cases, of course, more is needed than just the most optimal lighting in the trailer – for example, training – to get them to relax. The

researchers therefore recommend additional research to make trailer loading even safer for everyone, but these results certainly seem to be a step in the right direction.


The complete study “LED lighting eases and secures the loading of horses and appeases them during confinement in a stationary horse trailer” by Nicolas Pousset, Claire Neveu, Emmanuel Melac and Marion Ferard can be found here.

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