Topic:Environmental Stressors
Environmental stressors encompass a range of external factors that can impact the health and well-being of horses. These stressors include temperature extremes, humidity, air quality, noise, and changes in habitat or management practices. Horses may exhibit physiological and behavioral responses to these stressors, which can affect their overall health, performance, and welfare. Research in this area focuses on understanding how environmental variables influence equine physiology and behavior, as well as identifying management strategies to mitigate negative effects. This page compiles peer-reviewed research studies and scholarly articles that explore the effects of environmental stressors on horses, examining their impact on health, performance, and welfare.
Small airway disease as a vanguard for chronic obstructive pulmonary disease. Equine allergic small airway disease is a highly prevalent respiratory condition among the stabled horse population. With the assistance of new diagnostic tools such as bronchoalveolar lavage, the condition can be recognized in young performing horses. The pathophysiological and clinical features resemble an earlier stage of chronic obstructive pulmonary disease as determined by the appearance of specific inflammatory cells. Although environmental management is paramount in controlling the disease, proper selective therapeutic regimens are as important to reduce the concurrent inflammation and...
Radiation hazards from horses undergoing scintigraphy using technetium-99m. This paper quantifies the extent of the radiation hazard to personnel from horses undergoing scintigraphy using technetium99m methylene diphosphonate (99Tcm-MDP). From the data produced it is possible to derive safe working protocols which are comfortably within the legislated limits for whole body doses as set out in the Ionising Radiations Regulations 1985. Measurements were made of the surface and environmental activities which result from individuals undergoing scintigraphic evaluation and also from urine contaminated bedding. The use of both high and low activities in the assessment of th...
The prevalence of shedding of Cryptosporidium and Giardia spp. based on a single fecal sample collection from each of 91 horses used for backcountry recreation. Cryptosporidium parvum and Giardia duodenalis are now recognized as primary enteric pathogens in animals and humans. Regulatory agencies, such as the Environmental Protection Agency are under increasing pressure to reduce the concentration of these protozoa in surface waters. Given the popularity of recreational riding of horses on public land in California backcountry, concerns have been raised by various regulatory agencies as to whether horses used for backcountry recreation are a significant source of C. parvum and G. duodenalis for the environment. The prevalence of fecal shedding of Cryp...
Methanogenesis in monogastric animals. Studies of methanogenic bacteria present in monogastric animals are still scarce. Methanogens have been isolated from faeces of rat, horse, pig, monkey, baboon, rhinoceros, hippopotamus, giant panda, goose, turkey and chicken. The predominant methanogen in all except the chicken and turkey is species of Methanobrevibacterium. The chicken and turkey harbour species of Methanogenium. In pig the population of methanogenic bacteria is more than 30 times as dense in the distal colon as in the caecum. This finding is in agreement with the finding that the rate of methane production is much higher in...
Pulmonary function measurements during repeated environmental challenge of horses with recurrent airway obstruction (heaves). To evaluate the degree of reproducibility in clinical variables, blood gas measurements, and lung function variables, and the changes in these variables caused by exposure to moldy hay in naturally sensitized and control horses. Methods: The magnitude of variation in arterial blood gas and pulmonary function measurements were evaluated in a model of naturally acquired heaves. Horses with heaves and similarly aged control horses were studied prior to moldy hay challenge and again after the horses with heaves manifested clinical signs of airway obstruction. This cycle of testing was repeated 3 t...
Physiological responses in nonheat acclimated horses performing treadmill exercise in cool (20 degrees C/40% RH), hot dry (30 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions. The aim of the present study was to determine the effect of different environmental conditions on physiological response to exercise. Four winter acclimatised, nonheat acclimated horses of different breeds were exercised at 20 degrees C/40% RH (CD), 30 degrees C/40% RH (HD) and 30 degrees C/80% RH (HH). The exercise test was designed to represent the structure and intensity of a One star Speed and Endurance test (competition exercise test [CET]). All 4 horses were able to complete the full CET (60 min + 30 min active recovery) in CD and HD, but only one horse completed the CET in HH. Two horse...
Effects of exercise intensity and environmental stress on indices of oxidative stress and iron homeostasis during exercise in the horse. The effects of prolonged variable-intensity and short-term high-intensity exercise on indices of oxidative stress and iron homeostasis were compared in six fit horses under cool [20 degrees C, 40% relative humidity (RH)] or hot/humid (30 degrees C, 80% RH) environmental conditions. The exercise protocols were designed to simulate equine competition, including racing (intense exercise) or the speed and endurance phase of a 3-day event (prolonged exercise). Increased plasma concentrations of lipid hydroperoxides and haemolysate concentrations of oxidised glutathione (GSSG) were measured within 3...
Recent acute and subacute mycotoxicoses recognized in France. Successful investigation and prevention of mycotoxic problems requires close collaboration between scientists from several disciplines ranging from agronomists and technologists required during production of food and feeds, to toxicologists and pathologists examining the effects of mycotoxins on animals and man. Zootoxic metabolites following fungal infection result from four general mechanisms: (i) secondary fungal metabolism (mycotoxins, eg, aflatoxins); (ii) bioconversion of vegetal compounds (eg, dicoumarol); (iii) plant reactions (phytoalexins, eg, coumestrol); and (iv) plant-fungus assoc...
Selective brain cooling in the horse during exercise and environmental heat stress. Five horses were exercised on a treadmill [to central blood temperature (Tcore) approximately 42.5 degrees C]. Three of those horses were heated at rest in a climate room (53 degrees C, 90% relative humidity) (to Tcore approximately 41.5 degrees C). Temperatures were measured in the rectum, hypothalamus (Thyp), cerebrum, and cavernous sinus (Tsinus), on the skin of the head and midside, and Tcore. When Tcore increased above 38.5 degrees C, Thyp remained 0.6 +/- 0.1 degree C (SE) lower during heat exposure and 1 +/- 0.2 degrees C lower during exercise. During heat exposure, Tsinus was 2.2 +/- 0...
Electrolyte and total protein changes in nonheat acclimated horses performing treadmill exercise in cool (20 degrees C/40%RH), hot, dry (30 degrees C/40%RH) or hot, humid (30 degrees C/80%RH) conditions. Four horses (H, J, N and M) undertook a simulated competition exercise test (CET), designed to simulate physiological and metabolic stresses of the Speed and Endurance (S & E) test of a 3-day-event, under 3 different environmental conditions: 20 degrees C/40% relative humidity (RH) (cool, dry [CD] 2 sessions); 30 degrees C/40% RH (hot, dry [HD]) and 30 degrees C/80% RH (hot, humid [HH]) (Marlin et al. 1995a). Venous blood samples for electrolyte and total protein (TP) determinations were collected from indwelling catheters at predetermined time points throughout each CET and initial 30 min...
Heart rate response and plasma lactate concentrations of horses competing in the speed and endurance phase of 3-day combined training events. The exercise intensity of horses competing in 3-day combined training events at 3 different levels of competition (CCI, n = 7; CCI, n = 11; CCI, n = 23) was investigated. Environmental conditions during all events were cool with 100% cloud cover. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean +/- s.d. heart rate for all horses during each phase were: Phase A = 118 +/- 11 beats/min, Phase B = 179 +/- 22.7 beats/min, Phase C = 129 +/- 13.9 beats/min and Phase D = 174 +/- 19.6 beats/min. Mean +/- s.d. heart rates on Phase A and C were significantly different...
An index of the environmental thermal load imposed on exercising horses and riders by hot weather conditions. There is a need to determine objectively the environmental heat load imposed on horses competing to an international standard in 3-day-events in environments where there is likely to be a high level of radiation added to high ambient temperatures and relative humidity; the presently used FEI 'Comfort Index' is severely limited in its applicability. It is proposed that the Wet Bulb Globe Temperature (WBGT) Index be used. This index was originally established for man exercising strenuously under harsh climatic conditions with high solar radiation levels. It may be defined as: WBGT = 0.7Twb + 0.3...
Copper deficiency in cattle, sheep and horses caused by excess molybdenum from fly ash: a case report. A case of copper deficiency or molybdenum toxicosis in cattle, sheep and horses after heavy pollution of a pasture with fly ash is described. If the pastures had not been grazed by cattle and sheep as well as the horses, it would have been difficult to identify the reason for the intoxication in the horses. It is argued that molybdenum intoxication, although seldom seen in non-ruminants, was the cause of the deaths of the horses. It is suggested that the bioavailability of molybdenum in fly ash is high and therefore can cause equine intoxication.
Emergence of eastern encephalitis in Massachusetts. The 20th century emergence in Massachusetts of zoonotic eastern encephalitis was interpreted in terms of recorded environmental change. The main mosquito vector of the infection, Cs. melanura, appears to have been scarce in eastern North America before the 1930s. Its relative scarcity resulted from destruction of the swamps that had been lumbered or drained for farming in the 18th and 19th centuries. When swamps matured once again early in the 1900s, the formation of subsurface pools of water beneath mature trees would have increased the availability of breeding sites for this mosquito. Transm...
Application of PCR to a clinical and environmental investigation of a case of equine botulism. PCR for the detection of botulinum neurotoxin gene types A to E was used in the investigation of a case of equine botulism. Samples from a foal diagnosed with toxicoinfectious botulism in 1985 were reanalyzed by PCR and the mouse bioassay in conjunction with an environmental survey. Neurotoxin B was detected by mouse bioassay in culture enrichments of serum, spleen, feces, and intestinal contents. PCR results compared well with mouse bioassay results, detecting type B neurotoxin genes in these samples and also in a liver sample. Other neurotoxin types were not detected by either test. Clostrid...
Elemental status of grazing animals located adjacent to the London Orbital (M25) motorway. The elemental (Br, Cd, Cr, Cu, Mn, Ni, Pb, Se, V, and Zn) content of blood and wool or hair from animals (sheep, horses and alpacas) exposed to motor vehicle emissions alongside the London Orbital (M25) motorway is reported. Elemental values were determined by inductively coupled plasma mass spectrometry (ICP-MS) quality control assessment using flameless atomic absorption spectroscopy (for Pb, correlation coefficients of whole blood r = +0.87, and hair r = +0.82), and replicate (n = 10) analysis of the international reference material IAEA A13 Animal Blood. For Pb very good agreement was obta...
Survey of selected design and ventilation characteristics of racehorse stables in the Pretoria, Witwatersrand, Vereeniging area of South Africa. Stables housing more than 20 horses in training were surveyed in the Pretoria, Witwatersrand, Vereeniging area of South Africa. Most racehorses were kept in loose boxes, bedded on straw or sawdust and remained indoors while the stables were cleaned. The average floor area was 13 m2 and airspace was 55 m3 per animal. The average predicted minimum air change rate by natural convection in calm winds was 7.0 air changes per hour, which was reduced to 2.2 when the doors and shutters were closed. The survey showed that many of the stables had been built without due consideration to factors that migh...
Eastern equine encephalitis (EEE): a description of the 1989 outbreak, recent epidemiologic trends, and the association of rainfall with EEE occurrence. An Eastern equine encephalitis (EEE) outbreak in 1989 led to nine human and 196 equine cases, chiefly in coastal Atlantic and Gulf Coast counties. In the past two decades, EEE age-specific incidence and mortality rates have declined compared with earlier years. Analysis of rainfall patterns in areas where human EEE cases occurred between 1983 and 1989 revealed an association between occurrence of human cases and excess rainfall. The association was stronger with data from local weather stations than from statewide rainfall averages and the predictive models were best when applied to northern s...
Dung dispersal and grazing area following treatment of horses with a single dose of ivermectin. Environmental consequences of treating horses with recommended dosages of ivermectin paste were studied in two controlled experiments with 29 horses in Ohio. In 1988, dung dispersal rates were measured by changes in dry weight over time of 48 copromes (300 g) formed from feces taken from four treatment and four control horses 3 days post ivermectin treatment. There was delayed dispersal of copromes from horses treated with ivermectin in June, resulting in significantly heavier ivermectin copromes compared with those of control horses by September. There was no difference in ivermectin or contr...
Airborne dust and aeroallergen concentration in a horse stable under two different management systems. Airborne dust concentration (ADC) was measured in 2 different horse management systems using an Andersen cascade impactor in the box-stall, and a personal Marple cascade impactor attached to the halter to measure ADC in the breathing zone. The levels of aeroallergens implicated in chronic obstructive pulmonary disease were measured by radioallergosorbent-inhibition immunoassay. A conventional management system (System C) utilising hay feed and straw bedding, and a recommended environment (System R) utilising wood shaving bedding and a complete pelleted diet were studied. In the stall, total an...
Basis for regulation of selenium supplements in animal diets. Selenium was discovered 174 yr ago but, until 1957, was given little notice by biologists or was vilified as an agent that caused toxicity in grazing ruminants and horses in the northern Great Plains. After its status as an essential nutrient was established, Se received intense scrutiny, and hundreds of papers have been published dealing with its metabolic functions and the consequences of a Se deficiency. Because regions of Se deficiency are so extensive in the United States, great efforts have been made to gain Food and Drug Administration (FDA) approval for Se supplementation of animal die...
Cytogenetic monitoring of farm animals under conditions of environmental pollution. Cytogenetic examinations were carried out in 13 cattle farms, two herds of horses, one stag farm and 13 pig farms in areas with different levels of environmental contamination. The frequency of aberrant cells per 100 mitoses was 3.67 +/- 1.89 in pigs (n = 260) and 4.16 +/- 2.4 in herbivores (n = 497). This is a significant difference (p < 0.01). Ten times higher frequencies of chromatid exchanges were found in pigs. The examined herds were classified into three groups by the level of environmental contamination (satisfactory, impaired and severely impaired environment). Significant differen...
Serological survey of Rhodococcus equi infection in horses in Hokkaido. Serological survey of Rhodococcus equi infection in horses in Hokkaido was performed using ELISA. Of 2,879 horse sera, 318 (11.0%) gave antibody-positive (OD greater than or equal to 0.3) reactions. The antibody-positive rate of female was significantly higher (p less than 0.01) than that of male, and no statistical difference between Anglo-Arab and thoroughbred was detected in the antibody-positive rate. The maximum antibody-positive rate (27.1%) was shown at 14 years of age. The antibody-positive rates on the 160 farms were found to vary widely from 0 to 78.9%. A significant difference (p le...