Airborne particulates (PM10) and tracheal mucus: A case-control study at an American Thoroughbred racetrack

Changes in eating time, chewing activity and dust concentration in horses fed either alfalfa cubes or long-stem hay

BACKGROUND

Chewing is an essential physiological process in horses; yet, the physical form of feeds may affect their chewing and feeding behaviour with consequences for equine digestion and health.

OBJECTIVES AND METHODS

The present study evaluated the potential of a commercial forage cubes made from alfalfa and mixed meadow grasses to maintain chewing activity when compared with a traditional long and fibre-rich hay. An additional aim was to measure the dust formation during feeding. The experiment was a crossover design with six horses (11 ± 4 years old, mean ± SD), fed with 5 kg (as-fed basis) of their feed (long hay or alfalfa cubes) overnight. Eating and chewing activity was measured using the EquiWatch system with a sensor-based halter.

RESULTS

Data showed that by feeding the same amount of feed overnight, cube feeding led to 24% shorter eating time (on average 67 min less) and 26% fewer total chews compared to the long hay. On an hourly basis, horses also spent more time eating and chewing the long hay compared to the cubes. The cube feeding led to a higher dust concentration of the inhalable fraction (<100 μm), but not of the thoracic (<10 μm) fraction. Nevertheless, average dust concentrations were generally low for both cubes and hay, whereby both were of sound hygienic status.

CONCLUSION AND RECOMMENDATION

Our data suggest that feeding alfalfa-based cubes overnight generated shorter eating time and less chews than the long hay without major differences in the thoracic dust. Therefore, because of the decreased eating time and chews, alfalfa-based cubes should not be fed a sole forage source, especially when it is to be fed without restriction.

Effects of low-dust forages on dust exposure, airway cytology, and plasma omega-3 concentrations in Thoroughbred racehorses: A randomized clinical trial

BACKGROUND

Racehorses commonly develop evidence of mild asthma in response to dust exposure. Diets deficient in omega-3 polyunsaturated fatty acids (Ω-3) might exacerbate this response.

HYPOTHESIS

To compare dust exposure, bronchoalveolar lavage fluid (BALF) cytology, and plasma Ω-3 and specialized pro-resolving mediators (SPM) concentrations amongst racehorses fed dry hay, steamed hay, and haylage.

ANIMALS

Forty-three Thoroughbred racehorses.

METHODS

Prospective clinical trial. Horses were randomly assigned to be fed dry hay, steamed hay, or haylage for 6 weeks. Measures of exposure to dust in the breathing zone were obtained twice. At baseline, week-3, and week-6, BALF cytology was examined. Plasma lipid profiles and plasma SPM concentrations were examined at baseline and week 6. Generalized linear mixed models examined the effect of forage upon dust exposure, BALF cytology, Ω-3, and SPM concentrations.

RESULTS

Respirable dust was significantly higher for horses fed hay (least-square mean ± s.e.m. 0.081 ± 0.007 mg/m³ ) when compared with steamed hay (0.056 ± 0.005 mg/m³ , P = .01) or haylage (0.053 ± 0.005 mg/m³ , P < .01). At week 6, BALF neutrophil proportions in horses eating haylage (3.0% ± 0.6%) were significantly lower compared with baseline (5.1 ± 0.7, P = .04) and horses eating hay (6.3% ± 0.8%, P < .01). Plasma eicosapentaenoic acid to arachidonic acid ratios were higher in horses eating haylage for 6 weeks (0.51 ± 0.07) when compared with baseline (0.34 ± 0.05, P < .01) and horses eating steamed (0.24 ± 0.02, P < .01) or dry hay (0.25 ± 0.03, P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Steamed hay and haylage reduce dust exposure compared with dry hay, but only haylage increased the ratio of anti-inflammatory to pro-inflammatory lipids while reducing BAL neutrophil proportions within 6 weeks.

Effects of forages, dust exposure and proresolving lipids on airway inflammation in horses

OBJECTIVE

To investigate the role of omega-3 polyunsaturated fatty acids (Ω-3)-derived proresolving lipid mediators (PRLM) in the resolution of mild airway inflammation in horses.

ANIMALS

20 horses with mild airway inflammation.

PROCEDURES

Horses previously eating hay were fed hay pellets (low Ω-3 content; n = 10) or haylage (high Ω-3 content; 9) for 6 weeks. Dust exposure was measured in the breathing zone with a real-time particulate monitor. Bronchoalveolar lavage (BAL) was performed at baseline, week 3, and week 6. The effect of PRLM on neutrophil apoptosis and efferocytosis was examined in vitro. BAL fluid inflammatory cell proportions, apoptosis of circulating neutrophils, efferocytosis displayed by alveolar macrophages, and plasma lipid concentrations were compared between groups fed low and high amounts of Ω-3 by use of repeated measures of generalized linear models.

RESULTS

Dust exposure was significantly higher with hay feeding, compared to haylage and pellets, and equivalent between haylage and pellets. BAL fluid neutrophil proportions decreased significantly in horses fed haylage (baseline, 11.8 ± 2.4%; week 6, 2.5 ± 1.1%) but not pellets (baseline, 12.1 ± 2.3%; week 6, 8.5% ± 1.7%). At week 6, horses eating haylage had significantly lower BAL neutrophil proportions than those eating pellets, and a significantly lower concentration of stearic acid than at baseline. PRLM treatments did not affect neutrophil apoptosis or efferocytosis.

CLINICAL RELEVANCE

Despite similar reduction in dust exposure, horses fed haylage displayed greater resolution of airway inflammation than those fed pellets. This improvement was not associated with increased plasma Ω-3 concentrations. Feeding haylage improves airway inflammation beyond that due to reduced dust exposure, though the mechanism remains unclear.

Physical Activity in Polluted Air-Net Benefit or Harm to Cardiovascular Health? A Comprehensive Review

Both exposure to higher levels of polluted air and physical inactivity are crucial risk factors for the development and progression of major noncommunicable diseases and, in particular, of cardiovascular disease. In this context, the World Health Organization estimated 4.2 and 3.2 million global deaths per year in response to ambient air pollution and insufficient physical activity, respectively. While regular physical activity is well known to improve general health, it may also increase the uptake and deposit of air pollutants in the lungs/airways and circulation, due to increased breathing frequency and minute ventilation, thus increasing the risk of cardiovascular disease. Thus, determining the tradeoff between the health benefits of physical activity and the potential harmful effects of increased exposure to air pollution during physical activity has important public health consequences. In the present comprehensive review, we analyzed evidence from human and animal studies on the combined effects of physical activity and air pollution on cardiovascular and other health outcomes. We further report on pathophysiological mechanisms underlying air pollution exposure, as well as the protective effects of physical activity with a focus on oxidative stress and inflammation. Lastly, we provide mitigation strategies and practical recommendations for physical activity in areas with polluted air.

Increased Weekly Mean PM2.5, and NO2 Are Associated With Increased Proportions of Lower Airway Granulocytes in Ontario Horses

Ambient pollution is associated with the development and exacerbation of human asthma, but whether air pollution exposure is associated with lower airway inflammation in horses has not been fully evaluated. The Air Quality Health Index (AQHI) is an online tool used by asthmatic Ontarians to modify their outdoor activity when ambient pollution is high. A single AQHI value, falling on a scale from 1 to 10⁺, is calculated from measurements of fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃). Increased AQHI values predict an increased risk for presenting to a health care provider for assessment of asthma exacerbation, with a time lag of 0-9 days after an increase. Whether ambient air pollution is a risk factor for identifying increased lower airway inflammatory cells on cytologic evaluation of bronchoalveolar lavage fluid (BALF) of horses has not yet been explored. To investigate this relationship, case data including BALF cytology preparations from horses across southern Ontario, Canada, were retrieved from the Guelph Animal Health Laboratory's archives. Spanning the years 2007-2017, 154 cases were identified within a 41- by 30-km area surrounding the cities of Guelph and Kitchener. In 78 of 154 cases, cytologic reevaluation identified increased proportions of one or a combination of BALF neutrophils (mean 5%, range 0-15%), eosinophils (mean 2%, range 0-31%), and mast cells (mean 4%, range 0-10%). To assess the effect of lagged pollutant and temperature exposures in these 78 cases, weekly mean values of AQHI, PM_2.5, NO₂, O₃, and temperature were recorded for the 4 weeks prior to the date of the horse's presentation for respiratory tract evaluation. The relationship between ambient exposures and increased proportions of lower airway granulocytes was evaluated using a case-crossover design. Single unit increases in 2-, and 3-week lagged weekly mean PM_2.5 and NO₂, were associated, respectively, with an 11% (p = 0.04, 95% confidence interval, CI = 1.01-1.22), and 24% (p = 0.03, 95% CI = 1.08-1.43) greater risk of identifying increased lower airway granulocytes. These findings suggest that exposure to increased ambient pollutants is associated with lower airway inflammation in Guelph and Kitchener area horses.

Asymmetrical Pulmonary Cytokine Profiles Are Linked to Bronchoalveolar Lavage Fluid Cytology of Horses With Mild Airway Neutrophilia

Few data on cytokine profiles in bronchoalveolar lavage fluid (BALF) are available for racehorses with mild/moderate equine asthma (EA); cytological diagnosis being most frequently made from only one lung. The purpose of the study was to compare cytokine mRNA expressions and protein concentrations in BALF from both lungs. As part of a larger study, 250 ml saline was randomly instilled in one lung and 500 ml in the contralateral lung of 30 clinically healthy Standardbred racehorses. This procedure was repeated 72 h later, inversing the volume per lung. Cytological cut-off values for diagnosis of mild EA was neutrophil proportions > 10% when instilling 250 ml. Eleven horses that exhibited unilateral mild inflammatory cytology [i.e., normal cytology (<10% neutrophils) in the other lung] were enrolled. Protein concentrations were not significantly different between lungs, for any of the investigated cytokines. Relative mRNA expression of IL-1β (3.887 ± 0.929) and IL-10 (3.225 ± 0.516) were significantly higher in BALF from mild inflammatory lungs when compared with non-inflammatory ones (1.408 ± 0.337 and 1.488 ± 0.420, respectively); and also significantly correlated with neutrophil proportions (R = 0.45 and R = 0.58, respectively). These findings suggest that specific inflammatory response and/or regulation locally occurs within the lower airways.

Determination of the Moisture Content and the Generation of Airborne Particulate Matter From Various Types of Footing From Indoor Riding Arenas Considered to Have Optimal Rideability

It has been known for some years now that the occurrence of lameness in horses is closely related to the characteristics of the riding surface and that respiratory tract diseases can be induced by airborne particles. To ensure both optimal rideability (e.g., grip, elasticity, etc.) and low dust production, riding surfaces have to be regularly attended to, which also includes watering the floor. However, at present, it is not known what the individual moisture content of the various types of riding surface should be to ensure optimal rideability or what their potential for releasing dust is at the time of optimal rideability. The aim of the present study was to determine the moisture content, the density as weight/liter, particle size distribution and the release of airborne particulate matter (APM) with a diameter <10 μm (PM10) of the footing material from three types of indoor riding arena surfaces considered to have optimal rideability. Loose footing material samples were taken from the surfaces of 25 indoor riding arenas [5 pure sand (S), 10 sand-wood chips (SW), and 10 sand-fibre (SF)] and investigated under standardized conditions. The evaluation of the surface's rideability was carried out subjectively by the respective facility manager. The ambient particulate monitor TEOM 1400a was used to measure the PM10 production from the footing samples. Although, according to the facility managers, all of the investigated riding surfaces had optimal rideability at the time of sampling; obvious differences could be found with respect to their moisture content, density, particle size distribution, and release of APM, both between and within the 25 indoor arenas. The moisture content of SW (14.96 ± 4.00%) was significantly higher than that of SF (8.99 ± 2.95%; P = .0046), but the S moisture content (10.82 ± 2.65%) was not significantly different to either of them (S vs. SW: P = .0982 and S vs. SF: P = .2446). With respect to the release of APM, it could be shown that the average release from SF was 2.50-5.47 times higher than either for the S or SW (C_Sum-S: 12.81 mg/m³air, SW: 5.86 mg/m³air, and SF: 32.06 mg/m³air; t-test-S vs. SW: P = .3882, S vs. SF: P = .2560, and SW vs. SF: P = .0031). The reason for this was the extremely high APM release in three of the ten investigated SF samples. In addition, significant differences were also observed in the APM release within the three individual types of footing. Although no factors significantly affected the release of APM in either the S or SW footings, the density of the SF footing was found to have a significant influence on its APM production: the higher the density, the lower the APM release. The density itself was related to both the footing's moisture content and fiber content. The reason why SF footings with a low density (associated with a high fibrous material content) and a high moisture content tended to cause a greater release of APM is that there was a segregation of the fibrous material caused by the measuring technique used. This led to the fibrous material rising to the top of the sample resulting in a release of APM directly from this material. To prevent such a high release of particles from SF footings with a high fiber content occurring in practice, such footings should be regularly and adequately watered, and any segregation of the fibrous material should be prevented using suitable arena grooming techniques.

Airborne particulate size and concentrations in five Thoroughbred training yards in Newmarket (UK)

Despite their implication in the pathogenesis of lower airway inflammation, limited baseline data exists for airborne particulates in Thoroughbred racehorse stalls in the United Kingdom. This study documents airborne particulate size and concentrations in Newmarket training yards using a nephelometer (DustTrak DRX 8534, TSI). Each stall was sampled on a summer and winter day at three time points (morning, midday and evening). Minimum, mean and maximum/min ranges were calculated for the fraction of particulates with an aerodynamic diameter smaller than 2.5 μm (particulate matter (PM) 2.5) and 10 μm (PM10). Comparisons were made using Wilcoxon signed-rank test. Average particulate concentration ranges were 0.02-0.27 (summer) mg/m³, 0.01-0.37 (winter) mg/m³ for PM2.5 and 0.02-0.39 (summer) mg/m³, 0.02-0.60 (winter) mg/m³ for PM10. Statistically significant effects of season and time of day were established, resulting in implications for future studies investigating the effect of yard variables on airborne particulates.

Lower Airway Disease in the Athletic Horse

The airways are the first part of the pathway in the oxygen transport chain that is critical to excellent athletic performance, and the lower airways are considered the final gatekeeper before oxygen enters the blood and carbon dioxide exits. Horses are blessed with large airways and lungs that allow them to be superb athletes, but the down side of this largesse on the part of evolution is that unless they are truly elite athletes they may withstand noninfectious disease of the lower respiratory tract for months to years before the owner or trainer notices. The two conditions of the lower respiratory tract that affect the athletic horse during exercise are exercise-induced pulmonary hemorrhage and inflammatory airway disease. The former may be considered, at least at the onset, as a problem of physiology rather than a disease, and the latter is a disease primarily of domestication: both are widespread among the athletic horse population and account for an impressive number of horses that fail to perform to their potential. Because of the high demands for oxygen in the athletic horse, even minor insults to the oxygen-carrying capacity of the body can affect performance, so it is of critical importance to keep the lungs as healthy as possible.

Effect of ionization, bedding, and feeding on air quality in a horse stable

BACKGROUND

Organic dust is associated with Equine asthma. Ionization should reduce airborne dust levels.

OBJECTIVES

To determine the effect of ionization of air, type of bedding, and feed on the levels of airborne dust, endotoxin, and fungal colonies in horse stables.

ANIMALS

24 healthy University-owned horses occupied the stables.

METHODS

A randomized controlled cross-over study. Four units with 6 stables were equipped with an ionization installation (25 VA, 5000 Volt Direct Current). Horses were kept either on wood shavings and fed haylage (2 units), or on straw and fed dry hay (2 units). Measurements were performed with and without activated ionization, during daytime and nighttime, repeatedly over the course of a week and repeatedly during 4-6 weeks. Statistical analysis was performed using a mixed effect model with Akaike's Information Criterion for model reduction and 95% profile (log) likelihood confidence intervals (CI).

RESULTS

Ionization did not alter concentrations of dust, endotoxin, or fungi, fewer. In the units with straw and hay, the concentration of dust, endotoxin, and fungi (difference in logarithmic mean 1.92 (95%CI 1.71-2.12); 2.86 (95%CI 2.59-3.14); 1.75 (95%CI 1.13-2.36)) were significantly higher compared to wood shavings and haylage.

CONCLUSIONS AND CLINICAL IMPORTANCE

The installation of a negative air-ionizer in the horse stable did not reduce concentrations of dust, endotoxin, and viable fungal spores. The substantial effect of low dust bedding and feed is confirmed.

Multiple molecular detection of respiratory viruses and associated signs of airway inflammation in racehorses

Background

The potential involvement of viruses in inflammatory airway disease (IAD) was previously investigated through either serology or PCR from nasopharyngeal swabs (NS). The aims of this study were to determine the prevalence and incidence of viral genome detection by qPCR in the equine airways, and their association with respiratory clinical signs.

Methods

Both NS and tracheal washes (TW) were collected monthly on 52 Standardbred racehorses at training, over 27 consecutive months (581 samples). Equid herpesviruses (EHV)-1, −4, −2 and −5, equine rhinitis virus-A and -B (ERBV), equine adenovirus-1 and −2, equine coronavirus and equine influenza virus were systematically investigated in both NS and TW. Nasal discharge, coughing, tracheal mucus score and TW neutrophil proportions were simultaneously recorded.

Results

Genome for 7/10 viruses were detected at least once throughout the study; up to 4 different viruses being also concomitantly detected. Monthly incidence in TW was respectively 27.9% (EHV-5), 24.8% (EHV-2), 7.1% (ERBV), 3.8% (EHV-4), 1.9% (EAdV1) and 0.2% (EHV-1; ERAV). Neither agreement nor correlation between NS and TW was found for respectively genome detection and viral loads. Detection of viral genome in NS was not associated with any clinical sign. Coughing was significantly associated with TW detection of EHV-2 DNA (OR 3.1; P = 0.01) and ERBV RNA (OR 5.3; P < 0.001). Detection of EHV-2 DNA in TW was also significantly associated with excess tracheal mucus (OR 2.1; P = 0.02).

Conclusions

Detection and quantification of EHV-2 and ERBV by qPCR in TW, but not in NS, should be considered when investigating horses with IAD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0657-5) contains supplementary material, which is available to authorized users.