Go Soak Your Hay
By Kentucky Equine Research
For horses that are sensitive to inhaled irritants, hay can be a problem, as even the cleanest, best quality hay is likely to contain a moderate amount of fine dust material. When a horse plunges into a pile of hay, it inhales countless small particles of dust, mold spores, and fibrous plant material. Collectively known as the respirable dust concentration, or RDC, these fine particles can cause severe airway irritation in sensitive horses. Heaves, broken wind, and recurrent airway obstruction are terms for a condition that can manifest as mild coughing or severe bronchial spasms that preclude any sort of training or exercise.
Management steps include wetting or soaking hay before consumption, selecting alternative bedding materials, and removing horses from stalls during periods of peak activity. All of these strategies have been used to minimize RDC impact. A study conducted at the University of Edinburgh examined the effect of soaking hay on RDC in the horse’s breathing zone. The study was designed to determine the usefulness of brief hay immersion as opposed to longer soaking periods and to investigate how management of one stall influences the RDC in a neighbouring stall.
The hay soaking trial involved three hay treatments: dry hay, hay immersed in a bucket of water and then fed immediately, and hay immersed for 16 hours prior to feeding. These treatments were designated dry, immersed, and soaked, respectively.
According to the study conducted at the University of Edinburgh, there is not a great benefit to long periods of soaking hay compared to brief immersion, as both methods greatly reduced the amount of inhaled irritants.
For each treatment, 5 kg of hay contained in a hay net was placed in the same location in the stall. Wood shavings were used for bedding. The stall was prepared an hour before the horse – a 15-year-old mare familiar with the site and the sampling equipment – was brought in. The hay net was placed in the stall ten minutes later, and RDC monitoring was begun after a further ten minutes. For each treatment, mean and maximum RDC readings were recorded in the horse’s breathing zone during a two hour sampling period. Six repetitions were performed for each protocol.
The common air space tests were conducted in a stable with two side-by-side stalls. The stalls were separated by gates, sharing a common entrance and common air space above the divider. Two treatments were used: (1) haylage, wood shavings, and an open window, and (2) hay, straw bedding, and a closed window. The same mare was brought into the stall by 6:00 p.m. and was undisturbed until she was taken out to pasture at 8:30 a.m. Manure and dirty/soaked bedding were removed immediately after the horse left the stall.
Fresh bedding, if needed, was added daily, and hay or haylage was provided in a net suspended in the corner of the stall. The second stall contained no feed or bedding, and these materials were not stored in the vicinity of the building.
In the common air space study, the use of straw bedding was found to increase the respirable dust concentration. Storing hay and bedding in or near the stable may also impact air quality inside the barn.
Air sampling was conducted in both stalls. Eight days of sampling were done for each treatment. Mean and maximum RDC readings between the stalls were compared to determine the effect of treatment type and activity in one stall on air quality in an adjoining stall.
In the study of dry or immersed or soaked hay, there was a significant difference in RDC readings in the horse’s breathing zone for the three treatments. Feeding of immersed hay resulted in a 60 percent reduction in mean RDC compared with dry hay, and feeding of soaked hay resulted in a 71 percent reduction in mean RDC compared with dry hay. Readings of maximum RDC showed that feeding immersed hay resulted in a 53 percent reduction compared with dry hay, while feeding soaked hay resulted in a 34 percent reduction compared with dry hay.
In the common air space study, it was found that changing the management system in the first stall from hay, straw bedding, and a closed window to haylage, wood shavings, and an open window resulted in a significant reduction in background mean RDC in both stalls. Making this management change reduced the median RDC value in the stall containing the horse by 73 percent and in the second stall by 68 percent.
Having an open window in a stall resulted in better air quality with less inhaled dust.
Readings were higher during periods of greater stable activity. Of 32 maximum RDC readings, 26 were recorded while the stall was being mucked out or at another period of activity. There was a 19-fold increase in RDC in the first stall while it was being mucked out. There was also a nine-fold increase in RDC in the adjoining empty stall when the first stall was being cleaned.
Several conclusions can be drawn from this research. First, wetting hay before it is offered to horses can significantly reduce the concentration of dust in the horse’s breathing zone.
This study agrees with other research indicating there is not a great benefit to long periods of immersion as compared to brief immersion. Prolonged soaking of hay removes some soluble nutrients, so immersing or briefly soaking hay seems to be the most sensible course of action. Hay should be fed as soon as possible after wetting, as allowing hay to dry could allow RDC to increase.
Second, this study confirmed that optimizing the management system in one stall resulted in a significant reduction in RDC in an adjoining stall. It can be inferred that storing hay or bedding material in or near a stable may impact air quality for stalled horses. Since peak RDC levels tended to coincide with times of high stable activity such as mucking out and moving horses in or out of the stall, removing sensitive horses from the stable during these times should be considered.
Main Article Photo: Robin Duncan Photography
This article was published in the September 2011 issue of Canadian Horse Journal.