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American barn stabling, where indoor boxes are separated by bars rather than solid walls, can improve social bonding and contact between horses. But does this yard design increase or decrease stable dust?

Scientists at the Royal Agricultural University at Cirencester have just published an important research study.

They compared airborne respirable dust in American barns with levels in individual stables, using four different management regimes: dry hay and dry straw, haylage and dry straw, dry hay and shavings and, finally, steamed hay and shavings.

Air samples were taken mid-afternoon, when all the stirring up created by mucking out, feeding and grooming had settled, and from two points: in the middle of each stable and next to the manger or haynet, where the horses were feeding.

As expected, steamed hay and shavings made the least dust, while dry hay and dry straw generated more than 10 times more dust. But there were further findings.

Dry hay and shavings were dustier near the horse’s nose while he was feeding in the single stables, but not in the American barns. Haylage and dry straw were the opposite, in both types of stable, with more dust in the middle of the stable and less around the haynet.

Even though dry hay and straw were the dustiest, keeping horses on this management in American barns generated nearly three times the dust produced by dry hay and straw in single stables. The scientists concluded that steamed hay and shavings are best in all situations, that dry hay is never a good idea and that dry hay and dry straw should be out of the question for American barns.

Arena testing

A horse breathing dust when he is resting is one thing, but he will breathe more deeply and with greater effort when he is working. Dusty conditions during strenuous exercise might therefore put him at even greater risk of respiratory problems.

And how can dust impact on our own respiratory health as riders? The disease known as “farmer’s lung”, first documented and publicised in the mid-1900s in people working with dusty hay and straw, is now recognised as a significant industrial health concern in the agricultural sector.

Vets in Germany investigated dust levels in indoor riding arenas to consider whether this might be significant to both horses and riders.

They measured dust concentrations in the air in four representative indoor arenas. To standardise results and allow comparisons, they took air samples in the same way from all the schools: first, they sampled the air after a 10-hour rest period when there had been no use of the school and no harrowing, raking or levelling. They then introduced one horse for a standard schooling session consisting of a 12-minute walk and a five-minute trot, all conducted with the same routine of circles, ending each session with a three-minute gallop around the arena. Air was then sampled immediately after the horse left.

Samples were taken at two heights: the height of a horse’s nose and the height of a rider’s face. Three of the schools had a sand surface and the other a sand/woodchip mixture, while one school shared common airspace with indoor stables in the same building. Samples were taken every month for a year.

Respiratory risks

In all the indoor schools, dust levels were found to be 10 times higher than the air in towns where air pollution was considered a problem. Not only were there a lot of dust particles in the air, but the size of these particles was small enough to beat the upper airway filtering of both humans and horses, and get right down into the lungs.

There was far more dust in the air after the schools had been used for exercising just one horse – and the scientists were sure that more horses would have generated more dust. The arena with the air space shared with the stables was the dustiest, while the least dusty surface was the mixture of sand and woodchip.

There was more dust in the winter months in all of the schools, probably because surface watering was stopped when it was very cold. The surface with woodchip appeared to absorb more water and this probably explained its reduced dust levels. Finally, although the difference was small, samples taken at horse nose height were dustier than those from the rider’s face height.

The conclusion drawn is that dust in indoor schools is a real risk to both horses and riders. Outdoor schooling is a far better option. Woodchips are better than plain sand, but all indoor surfaces should be watered regularly to reduce dust levels.

Ref Horse & Hound; 1 June 2017