104 Shade use in dry lots by captive wild horses

Abstract

s / Journal of Equine Veterinary Science 35 (2015) 418e436 428 104 Shade use in dry lots by captive wild horses K.E. Holcomb*, and C.L. Stull University of California, Davis, Population Health and Reproduction, Cooperative Extension, School of Veterinary Medicine, Davis, CA, USA The Bureau of Land Management (BLM) is the federal agency charged with managing wild horses and burros that roam free on public lands in the United States. Animals are captured and removed from herd management areas in an effort to maintain herd numbers appropriate to promote healthy ecosystems. Recently, the BLM was challenged by members of the public to provide shade during hot weather for captive wild horses in short-term holding facilities. In our previous research, domestic horses showed a preference for available shade and benefitted during hot weather conditions. The objective of the current BLMfunded study was to characterize the use of shade by captive wild horses in holding facilities. The study was performed at the BLM’s Palomino Valley Wild Horse and Burro Center in Reno, NV from August 10 to October 1, 2014. Free-standing shade structures (9.1 m 4.9 m) were constructed in each of 2 dry-lot pens (25.9 m 10.7 m) with shade cloth covering the top that blocked 95% of UV radiation. A crossover design was used consisting of a group of 4 captive wild mares placed in each of the 2 dry lots. Data were recorded for 5 d and then the groups were switched to the opposite pen for 5 d. This protocol was repeated for 4 consecutive trials and a total of 8 groups of horses. Presence in the shade was recorded between 09:30 and 17:00 h from footage captured by time-lapse cameras at 10-s intervals. Automated weather stations placed in the sun and shade recorded daytime ambient temperature (25.9 ± 5.9 C), relative humidity (27.2 ± 16.4%), black globe temperature (35.6 ± 8.2 C in sun; 29.2 ± 6.6 C in shade), and solar radiation (595 ± 235W/m2). Two cloudless days in each trial were randomly selected for this preliminary analysis. The percentage of time in shade comparedwith percent of pen shadedwas analyzed with PROC TTEST (SAS 9.4). Bout data, with a bout defined as a horse present in shade for at least one minute, were generated using PROC SUMMARY (SAS 9.4). Descriptive statistics on bout data were calculated in MS Excel. Results showed wild horses spent 13.3% more time in shade than by chance (P < 0.001) within the dry lots onwarm, sunny days. Mean (±SD) time in shade/day/ horse was 125.3 ± 71.8 min; mean number of bouts in shade/day/ horse was 22.0 ± 12.1; mean bout duration was 5.7 ± 7.2 min. The results of the current study contribute additional evidence in developing standards of care for shade provisions during hot weather for both domestic and captive wild horses.