Equine Health: Dust and Ammonia Emissions from Eight Different Bedding Materials

In equine husbandry, dust and ammonia emmissions have an important impact on respiratory health. Eight different bedding materials were tested for these emissions using a standardized method.

A wide variety of different bedding materials is available on the market for equine husbandry. Different materials offer different properties of the bedding, including reduced dust or odour, mould suppression, ammonia binding capacity, compostability, high hygiene standards, absorbency and durability. The health and well-being of the horses are of central importance in choosing their bedding.

The respiratory tract of the horse is particularly sensitive to particles and harmful gases in the air, but it is also important to protect the respiratory health of the stable staff.

Experimental measurement of dust and ammonia emissions In the study, eight different bedding materials (wheat straw, wood granules, shredded paper, compost (Bio-Waldboden®), straw pellets, hemp with added eucalyptus, hemp and flax, and chinese reed or miscanthus) were tested under standardised conditions for their dust formation and ammonia binding capacity in order to exclude external influences such as stable climate and equine activity. To measure dust emissions, the bedding materials were placed in a rotating plastic box intended to simulate an extreme bedding use and the associated release of dust in the horse’s box. To measure the ammonia emissions, defined quantities of faeces and urine were added to bowls containing 400 g of bedding over seven days. The compost litter was also tested for ammonia emissions in quantities of 200 g and 1500 g.

Figure 1: Rotating plastic box for standardised dust measurement. (Foto: Jan Kocher, HAFL)

Main results

  • Hemp bedding with added eucalyptus resulted in the highest fine dust emissions (PM 2.5), followed by hemp and flax bedding, and wood pellets.
  • In contrast, the fine dust emissions from compost bedding were very low compared with the other types.
  • Twenty minutes after the bedding materials had been turned in the plastic boxes, their fine dust concentrations were still not below the recommended limits, with the exception of the compost bedding.
  • The ammonia (NH3) emissions from the bedding materials varied little on the different test days, but after five days they had all risen well above the recommended value of 10 ppm.
  • The ammonia emissions from the compost litter could be considerably reduced by using higher litter thickness, equivalent to 1500 g.
  • The dust concentrations measured do not provide clear information on the composition of the particles, but the content of organic dust, e.g. mould and mites, is considered critical for pulmonary health in horses.
Figure 2: Average PM 2.5 dust concentration of the eight different bedding materials from 0 to 20 minutes after the turning process in the plastic boxes.


  • Critical dust or ammonia emissions cannot be eliminated simply by the choice of bedding, which makes suitable bedding and stable management vitally important.
  • In some cases the fine dust concentration did not fall below the recommended limits 20 minutes after turning, which should be allowed for in daily husbandry, particularly after changing bedding and wiping down in the stable.
  • Bedding thickness would appear to be a significant factor in minimising ammonia emissions, particularly for compost bedding.
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