Animals 2015,5, 965-977; doi:10.3390/ani5040394 OPEN ACCESS
Reducing Respiratory Health Risks to Horses and Workers: A
Comparison of Two Stall Bedding Materials
Markku Saastamoinen 1, *, Susanna Särkijärvi 1and Seppo Hyyppä 2
1Natural Resources Institute Finland (Luke), Opistontie 10 a 1, 32100 Ypäjä, Finland;
2Ypäjä Equine College, Opistontie 9, 32100 Ypäjä, Finland; E-Mail: Seppo.hyyppa@hevosopisto.ﬁ
*Author to whom correspondence should be addressed; E-Mail: markku.saastamoinen@luke.ﬁ;
Academic Editor: Kirrilly Thompson
Received: 14 July 2015 / Accepted: 29 September 2015 / Published: 8 October 2015
Simple Summary: In this study, the effect of wood shavings and peat was examined on
stable air quality and health of horses and stable workers. The ammonia level in the boxes
in which peat was used as bedding was non-existent or very low. The respiratory symptoms
in horses increased regardless of the bedding material at the beginning of the study. The
health status of the horses on peat bedding returned to the initial level in the end of the trial
but horses in stalls bedded with wood shavings continued to be symptomatic. The hooves of
the horses in stalls with peat bedding had a better moisture content. The results suggest that
peat is a better bedding material for horses and people working or visiting horse stables than
Abstract: Stable air quality and the choice of bedding material are an important health issue
both in horses and people working or visiting horse stables. Risks of impaired respiratory
health are those that can especially be avoided by improving air quality in the stable. The
choice of bedding material is particularly important in cold climate conditions; where horses
are kept most of the day and year indoors throughout their life. This study examined the
effect of two bedding materials; wood shavings and peat; on stable air quality and health
of horses. Ammonia and dust levels were also measured to assess conditions in the stable.
Ammonia was not detected or was at very low levels (<0.25 ppm) in the boxes in which peat
was used as bedding; but its concentration was clearly higher (1.5–7.0 ppm) in stalls with
wood shavings as bedding. Personal measurements of workers revealed quite high ammonia
exposure (5.9 ppm8h) in the boxes in which wood shavings were used; but no exposure was
observed in stalls bedded with peat. The respiratory symptoms in horses increased regardless
of the bedding material at the beginning of the study. The health status of the horses in the
peat bedding group returned to the initial level in the end of the trial but horses bedded with
wood shavings continued to be symptomatic. The hooves of the horses with peat bedding
had a better moisture content than those of the horses bedded with wood shavings. The
results suggest that peat is a better bedding material for horses than wood shavings regarding
the health of both horses and stable workers.
Keywords: bedding material; respiratory health; peat; wood shaving
The stalls of horses are bedded to absorb urine, moisture, and gases and to increase the comfort,
health, and well-being of the horses. In addition, a large number of people are engaged in the horse
industry as trainers, riders, stable workers, farriers, and other roles working or visiting stables for many
hours daily, and being subjected to the inﬂuences of the stable environment. Most of them are young
people, for example riding school pupils.
Horses in northern climatic conditions (e.g., in the Nordic countries and Canada) are exercised
outdoors usually for 1 to 2 h and spend, consequently, the major part of the day (often up to 23 h) indoors.
Because of this, stable air quality is of considerable importance. Furthermore, training and racing in cold
weather conditions expose the vulnerable respiratory system to health problems, increasing inﬂammatory
cells in the lungs . As a consequence, respiratory disorders are common problems, and respiratory
allergy is commonly diagnosed as a condition affecting the equine lung. When the condition becomes
protracted it is referred to as chronic obstructive pulmonary disease (COPD) or heaves (or RAO, recurrent
airway obstruction), an animal model of asthma. Anecdotal reports suggest that the condition is rare in
climates where animals are outside all year around but is common in climates where horses are stabled
indoors . Clinical signs in horses with this chronic lung disease include poor athletic performance,
chronic couching, purulent nasal discharge, and ultimately difﬁculties in breathing [2,3].
People working in and visiting horse stables may also be exposed to the effects of the stable air.
Causes of chronic airway disease both in horses and humans usually involve exposure to excessive
concentrations of airborne dust, molds, viruses, bacteria, spores, aeroallergens, and endotoxins which
mostly originate from bedding and feed [4–7]. Furthermore, the inhalation of gaseous irritants such
as ammonia may initiate airway obstruction and exacerbate or prolong the clinical signs of COPD in
affected horses  as well as humans .
The effect of bedding material on the quality of stable air, both on stable dust and the ammonia
concentration, is signiﬁcant . The various forms of bedding in a stable and even the differences in
beddings between boxes within a stable  inﬂuence the stable dust and gas loads, and consequently the
risk to airway health of both horses and humans.
Currently, several materials are available for the bedding of boxes in horse stables. The most common
bedding materials are wood shavings, saw dust, straw, and peat. Many other materials are also used as
bedding, including processed (pelleted) wooden materials and (pelleted, chopped) straw from different
plants. In addition, shredded or cut paper and some plant materials (by-products), as well as woodchips
are used. Each of these has individual properties, including advantages and disadvantages . Stall mats
are also available, but they are usually used together with bedding because of the binding of urine. It has
also been reported that horses prefer bedding material for lying down as compared with areas without
Factors considered when selecting bedding are its availability, cost, cleanness (free from dust and
foreign material) and its effect on stable air quality. The bedding material should also be easy and light
to handle, to avoid excessive physical exertion in stable workers. From the point of view of horses’
health and well-being, good bedding creates a layer of insulation between the horse and cold ﬂoor,
pads the hard surface, prevents bruised knees, elbows, hocks and hips, and keeps the horse clean. The
bedding material also affects the behavior of horses [11–13], for example the incidence of stereotypic
behaviour. In addition, good bedding material has a better potential to be re-used e.g., in farming and
The objective of this study was to examine the effects of two different bedding materials, wood
shavings and peat, on the health of horses. This issue was evaluated on the basis of respiratory and
overall health and quality of hooves, and by measuring stable air quality.
2. Materials and Methods
The experiment was conducted in the facilities of MTT Agrifood Research Finland (MTT, currently
Natural Resources Institute Finland Luke) in the south western part of Finland (latitude 60˝) under
autumn/early winter (October to December) climatic conditions. The duration of the experiment was
84 days. Twelve Finnhorse brood mares (four of which were pregnant) aged between 5 and 17 years
were housed in box stables in individual stalls (3 m ˆ3 m), divided into separate sections of the stable
according to the bedding material (peat; wood shavings). The stable sections were of the same size and
had an identical mechanical ventilation system. The horses were held on pasture from the beginning of
June to the middle of September.
The two bedding materials were selected because they are the most common materials used for
bedding in Finland. They both have a low content of harmful components when manufactured, selected
and stored properly. Peat is favoured as a bedding material because of its good properties in soil
improvement and good composting ability, as well as its superior capacity to bind ammonia and
ﬂuid [13,16,17] compared to other materials. Both bedding materials were manufactured for use as
beddings in horse stalls; peat by Vapo Ltd. (Jyväskylä, Finland) and wood shavings by Joutsenon
purupaali Ltd. (Joutseno, Finland).
The horses were exercised daily in paddocks in groups for four hours, and for one hour by riding
or driving during the course of the experiment. The stalls were manually cleaned by the same person
between 8 and 12 am when the horses were in outdoor paddocks. All feces and wet material were
removed and new bedding material was added. The depth of the bedding was about 10 cm. All removed
and added bedding materials were measured by their volume.
The horses were individually fed according to their needs three times per day (morning, noon,
evening) with silage/haylage (DM 26.6%–6.9%) and pelleted compounded feed (DM 88%) (Suomen
Rehu Ltd., Turku, Finland) to minimize the release of airborne particles from the feeds. The diet was
balanced for protein (nitrogen) intake to avoid nitrogen lost in urine and, thus, to minimize the ammonia
in the stable. The forage was produced by MTT and its fermentation and hygienic quality fulﬁlled the
criteria of good quality haylage and silage . The forage was placed on the ﬂoor.
Outdoor temperatures and weather conditions were recorded daily at 8:00 am. The average outdoor
temperatures in October, November and December, respectively, were ´1.7 ˝C (´10 to 2 ˝C), ´3.8 ˝C
(´14 to 3 ˝C) and ´6.6 ˝C (´20 to 0 ˝C). According to the statistics of the Finnish Meteorological
Institute the temperatures in December were quite normal, but in November the daily temperatures were
highly variable, and in October the temperatures were exceptionally low.
The stable temperatures and humidity, as well as ammonia and carbon dioxide levels and amount of
dust, were measured daily in both stable sections. Methane (day 0) and hydrogen sulphide (days 0 and
42) contents were measured, but because of undetectable values the measuring was not continued. Gases
concentrations were measured at a height of 120 cm from the ground using an Accuro gas detection pump
which draws air through sampling tubes (Dräger Safety AG, Lübeck, Germany). The measurements were
carried out at 6:00 am in three boxes of each stable section; from the middle of the box at the level of the
muzzle of the horse. Dust was continuously collected into dust cases that were ﬁtted in empty boxes in
both stable sections at the level of 40 cm from the ground.
Exposure of the stable workers to ammonia was evaluated with personal measurements using
sampling tubes attached to the lapel of the person (Dräger Safety AG, Germany) in the middle and
at the end of the experiment during the cleaning of the stalls. The measurement result was converted
to correspond to an exposure period of eight hours (HTP8h) . HTP value is the concentration that is
harmful to people.
A respiratory endoscopic examination was performed three times during the study (days 0, 42 and
84), including examination of the ethmoidal region, pharyngeal openings of guttural pouches, soft palate,
larynx, and trachea (symptoms = 1; no symptoms = 0). Tracheobronchial aspirates were drawn during
the endoscopy and cytological and bacteriological (neutrophil cells) evaluation was carried out. The
classiﬁcation of the neutrophil cells in bronchoalveolar smear samples was as follows: none or some
single cells (´); single cells and few small pool of cells (+); several large pools of cells (++); abundant
pools of cells (+++); and an extreme abundance of cells (++++).
Blood analyses, fecal analyses and hoof quality evaluation were used as measures of health and
well-being of the horses. These samples were taken with the same interval as the endoscopic
examination. In addition, rectal body temperature was measured and, heart rate (with stethoscope)
and respiration rate via auscultation were recorded by a veterinarian researcher. Blood samples were
collected from the jugular vein, and the blood analysis consisted of hemoglobin, haematocrit, serum urea,
iron, protein, and differential cell count. Bacteriology, parasites, and the pH of faeces were determined.
The quality of hooves was assessed from the dry matter content of hoof horn. The hoof horn samples
were collected from the hooves of front legs when the horses were in shoeing. All samples were analyzed
in the clinical laboratory of MTT.
The experimental design was a randomized block design with repeated measurements. After the ﬁrst
endoscopy, the horses were formed into pairs based on their symptomatic similarity. The two horses
of each pair were then randomly allotted to different bedding material groups (peat bedding or wood
shaving bedding). The procedure was repeated until all horses were divided in the two groups. The
information from the ﬁrst endoscopy was excluded from the data because it was included in the animal
pair-variable in the model. The data (samples from horses) were analyzed using the MIXED procedure
of the SAS system with the following statistical model: Yijk =µ+ pi+ bj+(pˆb)ij + tk+(pˆt)jk +
(bˆt)jk + eijk, where Yijk is the observation, µis the overall mean, piis the random effect of ith animal
pair (i= 1 . . . 6), bjis the ﬁxed effect of jth bedding material (j= 1 . . . 2), tkis the ﬁxed effect of
the time period (k= 2 or 3), and eijk is the normally distributed error with a mean of 0 and variance
δ2. Terms (pˆb)ij, (pˆt)jk and (bˆt)jk are compound effects of factors. The best ﬁtting covariance
structure for repeated measurements was selected on the basis of the Akaike information criterion. The
differences were tested with Tukey’s test. Categorical variables (neutrophil cells in tracheal mucus) and
0/1-variables were not tested statistically, but were presented descriptively, because of the small number
of observations and their subjective scoring making them less informative.
In animal handling and sample collection, the European Union recommendation directives
(1999/575/EU) and national animal welfare and ethical legislation set by the Ministry of Agriculture and
Forestry of Finland were followed carefully. The experimental procedures were evaluated and approved
by The Animal Care Committee of MTT before the study was started. The endoscopic examination was
carried out and all samples from the horses were collected by a veterinarian researcher.
3. Results and Discussion
3.1. Air Quality
The average temperatures in the stable sections (peat bedding vs. wood shaving bedding) in October,
November and December, respectively, were 9.2 vs. 10.3 ˝C, 9.4 vs. 9.4 ˝C, and 8.0 vs. 8.0 ˝C. These
temperatures are within the target indoor temperature range (8–12 ˝C) in horse stables in Finland .
The average moisture content of the stable air (peat vs. wood shavings) was 54.3% vs. 54.6%, 56.0%
vs. 57.6% and 53.0% vs. 58.6% in the corresponding months. During the lowest outdoor temperatures
the moisture contents were naturally at the lowest levels (38% to 44%). The moisture of the stable
air originates from horses’ respiration, urine, feces and drinking and washing water. Excessively high
temperatures and moisture may increase the release of ammonia from the bedding .
The bedding material numerically inﬂuenced the ammonia content of the stable air (Table 1).
Measurements we made early in the morning before any other activity in the stables. Thus, the ammonia
concentrations represent the situation at its worst after the night. The ammonia level in the middle of
the boxes in which peat was used as bedding was non-existent or very low (<0.25 ppm). However, the
ammonia concentration in the stalls with wood shavings as bedding was numerically (6–8 times) higher
(1.5–7.0 ppm) and at the highest close to levels (10 ppm) considered harmful . The ammonia levels
observed in the present study were lower than recently reported gas levels in the morning in stables with
bedding consisting of pine wood shaving , but under warmer conditions (summer, in North Dakota,
US). Ammonia in the stable originates from urine. The urinary production depends the diet (N-intake)
and water intake. Both urinary production and N-losses increase with increasing N-intake . In the
present study the diet was individually balanced for protein (N) intake, and excretion of N was not
obviously very high. There were no differences in ammonia concentrations in the stalls of horses on peat
bedding (0–0.25 ppm) because of the superior ammonia absorption capacity of peat. Concerning the
horses on wood shavings bedding the ammonia content varied between the horses (stalls) and measuring
dates from 1.5 to 7.0 ppm.
Table 1. Gas concentrations in the stable air.
Wood Shaving Bedding Peat Bedding
Ammonia 0.5 ppm 0 ppm
Carbon dioxide 650 ppm 500 ppm
Hydrogen sulphide 0 ppm 0 ppm
Methane 0 ppm 0 ppm
Ammonia 1.5–7.0 ppm 0–0.25 ppm
Carbon dioxide 500 ppm 700 ppm
Hydrogen sulphide 0 ppm 0 ppm
Ammonia 4.0–7.0 ppm 0–0.25 ppm
Carbon dioxide 700 ppm 600 ppm
The amount of dust collected was small for both bedding types, and no major differences were
observed in dust measurements between the bedding materials. Both bedding materials were specially
manufactured for use in horse stalls. The carbon dioxide values were lower than the upper acceptable
limit values for horses (3000 ppm) and for humans (1000 ppm) . Carbon dioxide levels were similar
in both stable sections.
The bedding materials also affected the environment of the people working in the stables. Personal
measurements of the ammonium exposure of the workers revealed was higher (5.9 ppm8h) in the boxes in
which wood shavings were used. No exposure was observed in stalls bedded with peat. This is important
to consider, because workers can spend a considerable amount of time each day in the stables. In this
study it took about 13 min to clean one box. According to previous studies, feeding and handling of
feed take about 5 to 7 min per horse per day [25,26], and cleaning the stalls (mucking out, replacement
of bedding materials) takes approximately 10 min per horse daily if no machinery is used [25–27]. The
upper limit of HTP8h is, however, as high as 20 ppm .
Studies on peat as a bedding material are scarce. Airaksinen et al.  and Nikama et al.  have
reported a superior ability of peat bedding to bind ammonia, which is based on its low pH value. The
pH value of the peat for bedding (Vapo Ltd.) used in the present study was 4.0. The pH value of
wood shavings used here was not available, but according to a study the pH of wood shavings is higher
(pH 5.5) than that of peat . Peat tended to create a better stable environment than pelleted sawdust
due to higher absorption of ammonia and lower levels volatile organic compounds , but no differences
between the bedding materials were observed regarding the amount of dust. However, depending on its
origin, peat has been shown to vary widely in dustiness and hygienic quality .
According to several other studies, the type of the bedding material has a considerable effect
on stable dust, ammonia, bacteria, and endotoxin concentrations in horse stalls [4,7,23,29–31].
Fleming et al.  observed that the gaseous ammonia concentration was lowest when straw pellets
were used. The order based on ammonia concentrations among the studied bedding materials in their
study was straw pellets, linen, hemp, wood shavings, paper cuttings, and wheat straw. In a study by
Garlipp et al.  ammonia emissions from wood shavings were considerably lower than from straw.
In some studies mucking out and handling of bedding materials inﬂuenced the dust and gas (ammonia)
emissions in the stable [7,30,32]. In the present study, the ammonia content of the stable air was higher
when wood shavings were used, and during mucking exposure of ammonia occurred only in stalls bedded
with wood shavings, resulting from the superior ammonia binding capacity of peat.
Pelleting of the bedding material reduces the generation of airborne particles by the bedding
material . Fleming et al.  found the lowest particle generation with straw pellets. In their
two studies [7,30] they concluded that straw pellets may promote an improvement in the stable climate
in relation to airborne particle formation, ammonia binding and ammonia transformation. Pelleted
newspaper also appears to have a good potential as a bedding material for horses .
In one study  the researchers observed that the generation of airborne particles in straw, wood
shavings, ﬂax, and hemp can be reduced with a separation technology. They also found that the
generation of particles increased during the storage of the bedding.
Proper ventilation is important to remove moisture, gases, and dust and other particles from the stable.
However, in many cases the ventilation of stables does not provide adequate exchange of fresh air. Thus,
the quality and properties of the bedding material are of considerable importance.
3.2. Horse Health
The ﬁrst endoscopic examination at the beginning of the experiment revealed that 4 of the 12 horses
had respiratory symptoms (+ . . . +++). Thus, moving the horses from pasture to indoor housing in
the middle of September (two weeks before beginning of the study) appeared to expose the horses
to respiratory disease because of the air quality of the stable. In a Swedish study the highest dust
measurements were observed in winter when the stable doors were closed . Slightly increased airborne
bacteria levels were also observed in stables in September compared to other seasons in that study. In
the present study the frequency of respiratory symptoms increased in both groups during the ﬁrst half
of the study period, but then decreased in the horses bedded with peat such that the number of horses
with symptoms in this group was the same at the beginning and end of the experiment. In the horses
bedded with wood shavings the number of symptomatic horses remained larger than at the beginning,
being twice of that compared to the horses with peat bedding (Table 2). Thus, the peat bedding seemed
to be a better bedding choice than wood shavings regarding the health of respiratory tract.
The number of neutrophil cells did not differ between the groups (data not shown). The
tracheobronchial aspirates obtained during endoscopy contained either scarce or moderate numbers of
neutrophils (peat bedding: ´. . . ++; wood shavings bedding: 0 . . . +++). An elevated number of
neutrophils or the detection of Curschman’s spirals is suggested to correlate with CODP symptoms .
One of the horses bedded with wood shavings had a high neutrophil percentage and also spirals in its
sample at the second and third samplings, and was therefore diagnosed as a CODP horse at that time.
Table 2. Symptomatic horses based on endoscopy examination.
Bedding Horse Day 0 Day 42 Day 84
Horses with symptoms 2 4 4
during the experiment 10
Peat bedding Horse Day 0 Day 42 Day 84
10 0 1 1
11 0 0 0
12 1 0 0
Horses with symptoms 2 4 2
during the experiment 8
There were no statistically signiﬁcant differences in blood parameters of the horses between the peat
bedding and wood shaving bedding groups (data not shown). The parameters in all horses were within
the range of reference values. The bedding did not affect the respiration or heart rate of the horses
(data not shown). The microﬂora of feces was also unaffected by the bedding, which is in agreement
with Tanner et al.  and Hübinette . The pH value was somewhat lower (p= 0.01) in the horses
with peat bedding (6.78) than in those bedded with wood shavings (7.08) at the end of the experiment
(day 84), and the colour of their feces was darker, which was obviously a result of observed eating peat
in small amounts. Hübinette  found no effect of bedding material (wood shavings or peat) on the
The moisture content of the hoof horn at the end of the study was higher (p< 0.05) in the horses
bedded with peat (32.6%) compared to the horses with wood shavings as bedding (30.5%). In the
middle of the study the difference was not statistically signiﬁcant (peat 34.2%, wood shavings 33.2%).
Dryness of the hooves can cause problems when the natural elasticity and toughness is lost . The
weakening of the hoof mechanism can lead to hoof cracks and impose an additional strain on the legs.
Tanner et al. 
found that the hooves were dryer and more caked when phone book paper was used as
a bedding material than in horses bedded on sawdust.
The results supported by literature [17,30] suggest that bedding materials have the potential to affect
stable air conditions and animal health and welfare. However, in some studies, no differences have been
observed. For example Tanner et al.  found no difference in the respiratory health of horses when
bedded with either sawdust or (shredded and milled) phonebook paper. However, the choice of bedding
material is especially important in cold climatic conditions, which forces horses to be kept indoors for a
large part of the year.
Although there appears to be clear differences in the properties and inﬂuences between various
bedding materials and types, the quality and origin of a particular bedding is important regarding the
airborne dust concentrations originating from the bedding material [17,30,39], and stable owners and
managers should thus also pay particular attention to this issue when selecting bedding materials.
Horses appear to have individual preferences for bedding material, and no signiﬁcant overall
preference for example for either wood shavings or straw was observed . Werhan et al.  also
found individual differences, but the horses generally preferred straw. The authors concluded that on
the basis of the longest time being occupied, straw seems to support the welfare of the horse better than
wood shavings or straw pellets.
3.3. Consumption of the Bedding Materials
The consumption of bedding materials differed considerably. The consumption of peat was 59% of
that of wood shavings (by volume), obviously due to its superior ability to bind liquids. This affects the
cost of bedding as well as the need for storage for both bedding material and manure, thus inﬂuencing
the construction costs of the facilities.
3.4. General Discussion
An issue of increasing importance is the inﬂuence of manure on environment, which means that
the amount of manure produced should be minimal and that it should be easily used as a fertilizer or
in soil improvement [14,15], or even as a source of energy, for example in methane production .
Rapid composting and a good ability to bind and transfer nitrogen are important properties of peat
bedding requested by farmers and other users of manure. Poeplau et al.  reported positive trends in
organic carbon storage in Swedish agricultural soils due to increased horse industry and horse manure
use in agriculture during the past two decades. It is also important that the bedding material can be
easily handled in the stable, which is inﬂuenced, for example, by how it is packed, or how much it is
Peat is a good alternative for bedding material in those countries where it is produced for
agricultural/horticultural or energy use, for example in the Nordic and Baltic countries, Russia, Poland
etc. However, it is important to consider that agricultural peat soils should be managed sustainably
and that cultural and socio-economical aspects of peatlands are taken into account . In many
other countries, such as in The Netherlands and Germany, the percentage of remaining pristine mires
is small .
The battery of methods used to monitor indoor air quality and animal health in the stable was
limited in the present study. In addition, outdoor exercise of the horses makes this issue complicated
to investigate, regardless of the methods applied. Horses also individually differ in their sensitivity
to exposure to environmental factors, i.e., their genetic predisposition for example, to RAO . On
the other hand, many studies regarding airway health have been ﬁeld studies without a controlled or
standardised environment, e.g., examining bedding and feeding practices and outdoor exercise. The
ﬁndings of the present study suggest that further research with a large sample size would be warranted
in order to gain a better understanding on the effect of bedding materials on stable air quality and health
and wellbeing of horses.
The results suggest that choice of bedding material is of large importance regarding stable air quality,
at least in terms of the ammonia level. Both horses and people working in stables are exposed to ammonia
if the ability of the bedding material to bind gases and ﬂuids is poor. This may predispose both horses and
humans to airway diseases. Based on the results, peat is superior to wood shavings regarding the ability
to bind ammonia and reduce ammonia concentration and the risk of ammonium exposure of horses and
stable workers. It seems also that horses on peat bedding may have better airway health. The moisture
content of the hooves of the horses on peat bedding was higher compared to those bedded on wood
shavings. The ﬁndings suggest that further research with a larger sample size is warranted.
Markku Saastamoinen designed the experiment with Susanna Särkijärvi, who also analyzed the data.
Seppo Hyyppä took the samples and carried out the endoscopic examination and analyzed materials
concerned. Markku Saastamoinen wrote the paper.
Conﬂicts of Interest
The authors declare no conﬂict of interest. The study was partly ﬁnanced by Vapo Ltd. having no
role in the design of the study; in the collection, analysis, or interpretation of data; in writing of the
manuscript, and in the decision to publish the results.
1. Riihimäki, M.; Raine, A.; Elfman, L.; Pringle, J. Markers of respiratory inﬂammation in horses in
relation to seasonal changes in air quality in a conventional racing stable. Can. J. Vet. Res. 2008,
72, 432–439. [PubMed]
2. Derksen, F.J. Chronic Obstructive Pulmonary Disease. In Equine Respiratory Disorders; Beech, J.,
Ed.; Lea & Febiger: Malvern, PA, USA, 1991; pp. 223–235.
3. Elfman, L.; Wålinder, R.; Riihimäki, M.; Pringle, J. Air quality in horse stables. In Chemistry,
Emission Control, Radioactive Pollution and Indoor Air Quality; Mazzeo, D., Ed.; Intech: Rijeka,
Croatia, 2011; pp. 655–680.
4. Tanner, M.K.; Swinker, A.M.; Beard, M.L.; Cosma, G.N.; Traub-Dargatz, J.L.; Martinez, A.B.;
Olenhock, S.A. Effect of phone book paper versus sawdust and straw bedding on the presence of
airborne gram-negative bacteria, fungi and endotoxin in the horse stalls. J. Equine Vet. Sci. 1998,
18, 457–461. [CrossRef]
5. Tutluoglu, B.; Atis, S.; Anakkaja, A.N.; Altug, E.; Tosun, G.A.; Yaman, M. Sensitization to horse
hair, symptoms and lung function in grooms. Clin. Exp. Allergy 2002,49, 1–8. [CrossRef]
6. Berndt, A.; Derksen, F.J.; Robinson, N.E. Endotoxin concentrations within the breathing zone of
horses are higher in stables than on pasture. Vet. J. 2010,183, 54–57. [CrossRef] [PubMed]
7. Fleming, K.; Hessel, E.F.; van den Weghe, H.F.A. Generation of airborne particles from different
bedding materials used for horse keeping. J. Equine Vet. Sci. 2008,28, 408–418. [CrossRef]
8. Clements, J.M.; Pirie, R.S. Respirable dust concentrations in equine stables. Part 2: The beneﬁts
of soaking hay and optimizing the environment in a neighbouring stable. Res. Vet. Sci. 2007,83,
9. Saastamoinen, M. Bedding Choices for Horses—An Overview. In Housing and Management
of Horses in Nordic and Baltic Climate, Proceedings of the NJF Seminar 437 Housing and
Management of Horses in Nordic and Baltic Climate, Reykjavik, Iceland, 6–7 June 2011; NJF:
Reykjavik, Iceland, 2011; pp. 33–36.
10. Hunter, L.; Houpt, K.A. Bedding material preferences of ponies. Equine Athl. 1991,4, 17–19.
11. McGreevy, P.D.; Cripps, P.J.; French, N.P.; Green, L.E.; Nicol, C.J. Management factors associated
with stereotypic and redirected behaviour in the Thoroughbred horse. Equine Vet. J. 1995,27,
86–91. [CrossRef] [PubMed]
12. Mills, D.S.; Eckley, S.; Cooper, J.J. Thoroughbred bedding preferences, associated behaviour
differences and their implications for equine welfare. J. Anim. Sci. 2000,70, 95–106.
13. Werhahn, H.; Hassel, E.F.; Bachhausen, I.; van den Weghe, H.F.A. Effects of different bedding
materials on the behaviour of horses housed in single stalls. J. Equine Vet. Sci. 2010,8, 425–431.
14. Airaksinen, S. Bedding and Manure Management in Horse Stables. Its Effect on Stable Air Quality,
Paddock Hygiene and the Compostability and Utilization of Manure. Ph.D. Thesis, University of
Kuopio, Kuopio, Finland, 2006; p. 52.
15. Nikama, J.; Keskinen, R.; Närvänen, A.; Uusi-Kämppä, J.; Särkijärvi, S.; Myllymäki, M.;
Saastamoinen, M. The role of bedding material in recycling the nutrients of horse manure. In
Equi-Meeting Infrastructures Horses and Equestrian Facilities, Proceedings of the le Lion d’
Angers, France, 6–7 October 2014; Haras National du Lion: France, 2014; pp. 34–37. Available
online: http://urn.ﬁ/URN:NBN:ﬁ.fe201501081077 (accessed on 18 August 2015).
16. Greatorex, J.M.; Karlsson, S.; Tersmeden, M.; Steineck, S. Composting Horse Manure. In Inﬂuence
of Bedding Material on Ammonia Emissions; Swedish Institute for Agricultural and Environmental
Engineering: Uppsala, Sweden, 1998; p. 13.
17. Airaksinen, S.; Heiskanen, M.-L.; Heinonen-Tanski, H.; Laitinen, S.; Linnainmaa, M.; Rautiala, S.
Variety in dustiness and hygiene quality of peat bedding. Ann. Agric. Environ. Med. 2005,12,
18. Müller, C. Fermentation patterns of small-bale silage and haylage produced as a feed for horses.
Grass Forage Sci. 2005,60, 109–118. [CrossRef]
19. Kemian työsuojeluneuvottelukunta. HTP-values. In Työsuojelusäädöksiä 3; Ministry of Social
Affairs and Health: Tampere, Finland, 2002; p. 57.
20. Saastamoinen, M.; Jansson, H. Hevosen elinympäristö. In Hevosen Ruokinta ja Hoito;
Saastamoinen, M., Teräväinen, H., Eds.; ProAgria Maaseutukeskusten Liitto: Porvoo, Finland,
2007; pp. 126–138. (In Finnish)
21. Pratt, E.V.; Rose, S.P.; Keeling, A.A. Effect of ambient temperature on losses of volatile nitrogen
compunds from stored laying hen manure. Bioresour. Technol. 2002,84, 203–205. [CrossRef]
22. Zeitler-Feicht, M.H.; Bohnet, W.; Düe, M.; Esser, E.; Pollmann, U. Positionspapier zu den
Leitlinien zur Beurteilung von Pferdehaltungen unter Tierschutzgesichtspunkten. Available online:
http://www.tierschutz-tvt.de/positionspapierpferdehaltung.pdf (accessed on 18 August 2015).
23. Borhan, S.; Rahman, S.; Hammer, C. Water absorption capacity of ﬂax and pine horse beddings
and gaseous concentrations in bedded stalls. J. Equine Vet. Sci. 2014,34, 611–618. [CrossRef]
24. Frape, D. Equine Nutrition and Feeding, 2nd ed.; Blackwell Science: Oxford, UK, 1998; p. 564.
25. Korkiamäki, H.; Lahin, P.; Laaksonen, K. Horse Stable Work and Estimated Working Hours;
TTS-Institure: Rajamäki, Finland, 1998; p. 6.
26. Laitinen, I. Manure Handling with Machinery in the Horse Stables. Master’s. Thesis, Department
of Agricultural Engineering, University of Helsinki, Helsinki, Finland, 2007; p. 53.
27. Kontioniemi, K. Vacation Replacement Service’s Service Plan for Horse Farms. Bachelor’s Thesis,
HAMK University of Applied Sciences, Hämeenlinna, Finland, 2012; p. 28.
28. N’Dayegamiye, A.; Isfan, D. Chemical and biological changes in compost of wood savings,
sawdust and peat moss. Can. J. Soil Sci. 1991,71, 475–484. [CrossRef]
29. Woods, P.S.; Robinson, N.E.; Swanson, M.C.; Reed, C.E.; Broadstone, R.V.; Derksen, F.J. Airborne
dust and aeroallergen concentration in a horse stable under two different management systems.
Equine Vet. J. 1993,25, 208–213. [CrossRef] [PubMed]
30. Fleming, K.; Hessel, E.F.; van den Weghe, H.F.A. Evaluation of factors inﬂuencing the generation
of ammonia in different bedding materials used for horse keeping. J. Equine Vet. Sci. 2008,28,
31. Garlipp, F.; Hessel, E.F.; van den Weghe, H.F.A. Characteristics of gas generation (NH3, CH4, N2O,
CO2, H2O) from horse manure added to different bedding materials used in deep litter bedding
systems. J. Equine Vet. Sci. 2011,31, 383–395. [CrossRef]
32. Sadegh, M.; Wouters, I.M.; Houben, R.; Heederik, D.J.J. Exposure to inhable dust, endotoxins,
beta (1–3) glucans and airborne microorganisms in horse stables. Ann. Occup. Hyg. 2009,53,
33. Ward, P.L.; Wohlt, J.E.; Zajac, P.K.; Cooper, K.R. Chemical and physical properties of processed
newspaper compared to wheat straw and wood shavings as animal bedding. J. Dairy Sci. 2000,83,
34. Garlipp, F.; Hessel, E.F.; van der Hurk, M.; Timmermann, M.F.; van den Weghe, H.F.A. The
inﬂuence of a particle separation technology on the generation of airborne particles from different
roughages and bedding materials used for horses. J. Equine Vet. Sci. 2010,30, 545–559.
35. Clarke, A.F. Chronic pulmonary disease—A multifaceted disease complex in the horse. Ir. Vet. J.
36. Hübinette, L. Effects of Peat and Wood Shavings as Bedding on the Faecal Microﬂora of Horses;
Swedish Agricultural University: Uppsala, Sweden, 2010; p. 21.
37. Douglas, J. Mechanical aspects of the equine hoof wall. Equine Athl. 1994,7, 15–20.
38. Tanner, M.K.; Swinker, A.M.; Traub-Dargatz, J.L.; Stifﬂer, L.A.; McCue, P.M.; van der Wall, D.K.;
Johnson, D.E.; Vap, L.M. Respiratory and environmental effects of recycled phone book paper
versus sawdust and bedding for horses. J. Equine Vet. Sci. 1998,18, 468–475. [CrossRef]
39. Vandeput, S.; Istasse, L.; Nicks, B.; Lekeux, P. Airborne dust and aeroallergen concentrations in
different sources of feed and bedding for horses. Vet. Q. 1997,19, 154–158. [CrossRef] [PubMed]
40. Wartell, B.A.; Krumins, V.; Alt, J.; Kang, K.; Schwab, B.J.; Fennell, D.E. Methane production
from horse manure and stall waste with softwood bedding. Bioresour. Technol. 2012,112, 42–50.
41. Poeplau, C. Positive trends in organic carbon storage in Swedish agricultural soils due to
unexpected socio-economic drivers. Biogeosciences 2015,12, 3241–3251. [CrossRef]
42. Takko, A.; Vasander, H. Socioeconomic Aspects of Commercial Uses of Peatlands in Finland.
In Wise Use of Peatlands, Proceedings of the 12th International Peat Conference, Tampere,
Finland, 6–11 June 2004; Päivinen, J., Ed.; Finnish Peatland Society: Tampere, Finland, 2004;
43. Leupold, S. Recreation—A Complementary after-use Option for Cutway Peatlands. In Wise Use
of Peatlands, Proceedings of the 12th International Peat Conference, Tampere, Finland, 6–11 June
2004; Päivinen, J., Ed.; Finnish Peatland Society: Tampere, Finland, 2004; pp. 1190–1193.
44. Marti, E.; Gerber, H.; Essich, G.; Oulehla, J.; Lazary, S. The genetic basis of equine allergic
diseases. 1. Chronic hypersensitivity bronchitis. Equine Vet. J. 1991,23, 457–460. [CrossRef]
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