Travelling horses

It is currently common practice for horses to be contained in a confined space for prolonged periods of time, whether it is while they are stabled or being hauled from place to place. There has been lots of published research looking into the dust environment surrounding horses while they are stabled, however nothing so far has looked at the impact of dust when trailering horses.

By Rosie Hutchins BSc (Hons). | Equestrian Writer

This study examined the dust environment while travelling a horse in a trailer and if different treatments of the forage could affect this. The chosen forage was hay and the three treatments included dry, soaked and steamed. This was a continuation of research done looking into the treatment of hay and the effect it has on the breathing zone of stabled horses. The current research and understanding are that the surrounding respirable dust environment during periods of being stabled can be very changeable and have a major effect on the horses health.

Horses are highly sensitive to dust and mold particles therefore excessive inhalation of these could lead to breathing problems, both short and long term. This has been shown to be the case in stables but it is yet to be seen if these factors have the same effect while travelling (Curtis 1996, Waran 2002, Moore-Colyer 2015, Clements 2006, McGorum 1998, Woods 1993, Jones 1989 and Niedzw 2014).

Taking information from various comparable studies helped with making predictions for possible outcomes. It had been found that the airborne dust concentrations were significantly greater around a horse’s breathing zone compared to the general stable environment. This is significant because when horses travel in trailers, hay nets are often placed very close to their muzzle. While a horse is eating forage, ventilation makes only a very small impact therefore changing the treatment to the forage will have the biggest impact on the dust environment.

Performance horses exert a large amount of energy for their chosen discipline and the respiratory system is of great importance to being able to compete to the best of their athletic ability. Respiratory conditions such as recurrent airway obstruction (RAO) can be very damaging to a horse’s performance career, with the respiratory system proving to be the most limiting factor in a racehorse. This therefore makes any improvement to a horse’s dust environment whether it be while stabled, trailering or both very important to ensure as high a quality of performance as possible. This even applies to recreational horses that should remain in the best health possible.

The set-up of the experiment was for three hay nets to be prepared and each to be weighted at 5kg (<50g>) before treatment to ensure all had the same dry weight. All hay nets were tied to the same place in the trailer, along with the air sampler in the horses breathing zone (See picture). For soaking the hay, a time of 30 minutes was decided from previous experiments. Steaming the hay was done in a HG2000 for a period of 50 minutes to ensure temperature reached over 80°C.

The horse was then trailered for 30 minutes with each hay net before it was swapped for another which had undergone a different treatment. This time of 30 minutes had been determined by a pilot study which had been undertaken to determine the most appropriate time for a suitable amount of dust to be collected. Once the data had been collected the filter papers were taken to the labs and studied under the microscope so the dust particles could be counted.

"Steaming is therefore shown to be the most effective treatment for reducing respirable particles when trailering your horse.

The expected results, following the previous research, would be that the steamed hay would produce the least amount of dust particles and the dry hay the most. This previous research looked at treating hay for horses that were stabled. In addition to looking into whether forage affected the respirable dust environment, the experiment also used four different horses to determine if individual behavior had an effect. The results were not statistically significant for this factor. While this is often a factor in stabled horses, due to the limited space in a horse trailer, it has less of an impact.

The results then showed there to be statistical significance (P<0.001) for the treatment of forage making a difference to the dust environment in the breathing zone. Dry hay produced the highest amount of dust particles, followed by soaked hay and finally steamed hay producing the least amount. Steaming is becoming a much more popular way to treat hay, and in this experiment, it was shown that soaking hay produced twice as many dust particles in comparison to steaming.

It has also been shown in a previous study that steaming hay not only improved the dust environment in the immediate breathing zone of stabled horses but also in the general stable environment. This could make it even more appropriate for horses that are trailered, especially for multiple horses, due to the confined space any improvement to the general environment would greatly benefit the horse’s health. Steaming is therefore shown to be the most effective treatment for reducing respirable particles when trailering your horse.


Curtis, L., Raymond, S. and Clark, A. (1996) Dust and ammonia in horse stalls with different ventilation rates and bedding. Aerobiology

Jones, W. E. (1989) Equine Sports Medicine. Lea and Fibiger

McGorum, B. C., Ellison, J. and Cullen, R. T. (1998) Total and respirable airborne dust endotoxin concentration in three equine management systems. Equine Veterinary Journal. 30: 430-434

Moore-Colyer, M. J. S., Taylor, J. L. E. and James, R. (2015) The effect of steaming and soaking on the respirable particle, bacteria, mould and nutrient content in hay for horses. Journal of Equine Veterinary Science. 39: 62-68

Niedzwiedz, A. (2014) Equine recurrent airway obstruction. Mac Vet Rev 37 (2): 115-120

Waran, N. (2002) The welfare of horses. Vol. 1. Kluwer Academic Publishers

Woods, P., Robinson, N., Swanson, M., Reed, C., Broadstone, R. and Derksen, F. (1993) Airborne dust and aeroallergen concentration in a horse stable under two different management systems. Equine Veterinary Journal. 25(3): 208-213


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