Housing recommendations for horses invariably include providing access to shade on hot, sunny days, but the potential benefits have not been scientifically studied. This experiment measured physiological, behavioral, and serological responses of horses confined individually to completely shaded (SH) or completely unshaded (SUN) drylot pens during the summer in Davis, CA. Twelve healthy adult horses in a crossover design experienced both treatments for 5 d each. Rectal temperature, respiration rate, skin temperature, and sweat scores were recorded hourly from 1230 to 1730 h daily. Observations were recorded from 1200 to 1800 h for proximity to water, foraging, locomotion, and insect avoidance behaviors. Daily blood samples were obtained to measure cortisol, hematocrit, and neutrophil-to-lymphocyte ratio. Automated and handheld sensors were used to record environmental conditions. The mean ambient temperature from 1200 to 1800 h during the study was 30.6 °C. Rectal temperature was greater for horses in SUN than for SH (mean 37.8 °C and 37.5 °C, respectively, SE = 0.06, P = 0.002) as was respiration rate (25.5 and 20.5 breaths/min, SE = 1.3, P = 0.008), and skin temperature (35.6 °C and 34.6 °C, SE = 0.1, P< 0.001). Horses in SUN showed sweat in 51.4% of observations vs. 1.1% for horses in SH. Horses in SUN spent more time than SH horses standing near their water source (34.0% of observations vs. 20.2%, SE = 0.3, P = 0.004). No differences were observed for foraging, locomotion, or insect avoidance behavior (P > 0.05). Cortisol concentrations were greater in SUN than SH (3.4 and 2.6 μg/dL, respectively, P < 0.001) but remained within the normal range for resting horses. No treatment differences were observed for hematocrit or neutrophil-to-lymphocyte ratio (P > 0.05). Horses exhibited treatment differences in the physiological measures first, most notably in rectal temperature at 1230 h, corresponding to peak solar radiation. Behavioral responses followed these physiological changes, with treatment differences in time standing near water becoming apparent at 1400 h as ambient and black globe temperature increased. Our results indicate that both the SH and SUN treatment groups exhibited thermoregulatory responses to these summer conditions and horses benefited from shade, as it mitigated these physiological and behavioral changes. These results are applicable in developing best management practices for the care of domestic horses.
Closure of US equine slaughter facilities in 2007 along with the concomitant economic recession have contributed to a sharp increase in the number of unwanted horses throughout the United States, with estimates totaling 100,000 horses per year. The objective of the study was to obtain comprehensive data regarding nonprofit organizations caring for unwanted horses, along with the characteristics and outcome of horses relinquished to these organizations. Nonprofit organizations that accept relinquished equines were contacted to participate in a 90-question survey. Responding organizations (144 of 326 eligible) in 37 states provided information on 280 cases representative of the 7,990 horses relinquished between 2007 and 2009. Data collected characterized these organizations as being in existence for 6 yr, financially supported through donations and personal funds, dedicated to the care of only 10 to 20 horses on a property of just over 30 acres, and reliant on volunteers for help. Funding was the greatest challenge to continued operation of nonprofit equine organizations, with maintenance costs for the care of a relinquished horse averaging $3,648 per year. Financial hardship, physical inability, or lack of time to care for the horses by owners were the most common reasons for relinquishment, followed by seizure through law enforcement agencies for alleged neglect or abuse. Relinquished horses consisted of mostly light horse breeds (79.3%), with Thoroughbreds and Quarter Horses as the most represented breeds. The age of relinquished horses ranged from 3 d to 42 yr old (12.4 ± 0.5 yr). About one-half of the horses entered in the survey were considered unhealthy due to illness, injury, lameness, or poor body condition. For every 4 horses relinquished to a nonprofit organization, only 3 horses were adopted or sold between 2006 and 2009, and many organizations had refused to accept additional horses for lack of resources. The estimated maximum capacity for the 326 eligible registered nonprofit equine rescue facilities of 13,400 is well below the widely published estimate of 100,000 horses that become unwanted in the United States every year. Nonprofit equine rescue and sanctuary facilities have historically played an important role in safeguarding the welfare of horses in society, but funding and capacity are limiting factors to their potential expansion in continuing to care for the current population of unwanted and neglected horses in the United States.
Provision of shade is recommended by best practice guidelines for horses living in hot, sunny environments despite a lack of research focused on potential benefits. We found in a previous study that horses without access to shade showed greater rectal temperature (RT), respiration rate (RR), and skin temperature (SK) and exhibited more sweat than horses that were completely shaded. Yet not known is whether horses will choose to stand in the shade when given a choice of areas with and without this resource. Our objective was to assess horse preference for shaded and unshaded areas in the hot and arid, sunny summer weather in Davis, California. For this preference test, 12 healthy, adult horses (6 mares, 6 geldings) were randomized into 3 sequential trials using 4 horses in each trial. The trials consisted of 2 d of acclimation and either 5 d (Trial 1) or 7 d (Trials 2 and 3) of observation. Horses were housed individually in dry lot pens. Half of each pen was covered by an open-sided shade structure. The amount of the pen shaded varied slightly throughout the day with a mean of 50.1% of the pen shaded. Physiological measurements (RT, RR, SK, sweat score) were recorded at 0900, 1230, and 1800 h. Behavioral observations (horses' location relative to shade, time spent walking, foraging, and standing) were recorded at 5-min intervals from 1300 to 1800 h daily and at 10-min intervals from 1800 to 1300 h on alternate days. Insect avoidance behavior was recorded for 1 min/h for each horse. Weather factors were recorded every 5 min, 24 h/d throughout the study; mean daytime ambient temperature was 29 °C ± 5 °C. Data were analyzed using PROC MIXED in SAS. Horses were located in the shade in 7.1% more observations than by chance (SE = 1.3, P < 0.001), with greatest use before and during peak solar radiation and then again following peak black globe temperature. Horses performed more walking and foraging behavior in the shaded areas (P < 0.01). Our research indicates that individually housed horses prefer shade when it is available in hot, sunny environments. These results support recommendations for access to shade when developing best practice guidelines for the care of domestic horses.
The Federation of Animal Science Societies (FASS) recommends providing access to shade for horses in hot, sunny weather at equine facilities. Previously, we found that healthy, mature domestic horses use shade with behavioral and physiological benefits during those weather conditions. The objective of this study was to characterize preference, frequency, and duration of shade use by healthy, mature horses in a Bureau of Land Management (BLM) holding facility during hot, sunny weather. The study took place at the BLM's Palomino Valley Wild Horse and Burro Center in Reno, NV, from Aug. 10 to Oct. 1, 2014. Freestanding shade structures were constructed in each of 2 drylot pens with shade cloth covering the top that blocked 98% of UV radiation. A group of 4 mares was placed in each of the 2 pens. After a 2-d acclimation period, data were recorded for 5 d, the horses were moved to the opposite pen, and data collected for an additional 5 d. This schedule was repeated for a total of 4 consecutive trials and 32 horses. Footage from time-lapse cameras was viewed at 10 s intervals between 0930 and 1700 h to record each horse's position relative to shade. Dosimeters secured to horses' halters recorded UV exposure. Automated weather stations recorded daytime ambient temperature (mean 25.9°C [SD 5.8]), relative humidity (mean 25.4% [SD 17.1]), black globe temperature (mean 29.3°C [SD 6.5] in shade and 35.8°C [SD 8.0] in unshaded area), and solar radiation (mean 595 W/m [SD 235]). Horses spent 10.9% more time in shade than by chance ( < 0.0001) within the drylots across all 40 study days. Mean daily time spent in shade was 107.9 min/horse (SD 66.9), comprising 17.1 bouts (SD 12.1) with an average bout length of 6.3 min (SD 3.4). The mean daily UV Index experienced by horses in these partially shaded drylots was 1.52 (SD 0.58) compared with 3.4 (SD 1.5) for a control instrument in the sun. Horses used shade more on the sunniest days and greater than just by chance at all hours of the day, with greatest use in the morning before peak ambient temperature. This study supports the FASS recommendation for provision of shade and may be useful in management and facility design for both domestic and captive wild horses.
Horses in the United States are commonly managed in outside pens or pastures in small groups. Limited research on shade use by domestic horses housed singly in individual pens has shown benefits and a preference for using available shade. The objective of this study was to examine the amount of shade use and the behavioral and physiological responses of small groups of horses when housed with access to shade (SH) and without access to shade (SUN). Thirty-six horses were randomized into 3 consecutive trials using 3 horses per group and 4 groups per trial. Groups experienced 5 d in each treatment in a crossover design. Weather factors were measured with automated sensors 24 h/d throughout the study. The mean afternoon ambient temperature was 31.0°C with relative humidity of 32%. Rectal temperature, respiration rate, and skin temperature were recorded at 1000, 1330, and 1900 h daily. Venous blood samples were obtained on Days 0 and 5 to measure serum cortisol, the neutrophil:lymphocyte ratio, and hematocrit. Behavioral observations for presence in shade, standing near or away from water, locomotion, and foraging were recorded at 5-min intervals from 1400 to 1900 h daily. Insect avoidance behaviors were recorded hourly during that same time period for 1 min/horse. Horses in the SH treatment were observed using shade in 7.1% of observations between 1400 and 1900 h, and behavioral differences were observed between the SH and SUN treatments. When in the SUN treatment, horses stood near the water troughs more (18.5 vs. 14.2% of observations; = 0.029) and foraged less (29.3 vs. 33.8% of observations; < 0.001) than when in the SH treatment. There were no treatment differences for other behaviors or for physiological measures ( > 0.05). Provision of shade structures accessible to groups of mature, healthy horses in hot, sunny environments should be considered in developing future guidelines for best management practices for horses.
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