The Effects of Ambient Temperature and Relative Humidity on Blood Parameters in Horses During Long-Distance Flights





At Schiphol Amsterdam airport more horses needed treatment for fever arriving after long-distance flights (>5 h) from hot and humid places than from temperate climate places. Our aim was to explain this finding by determining blood parameters with predictive value for early onset of illness in horses during commercial long-distance flights.


Blood was drawn prior to loading (Sample 1), halfway during the flight (Sample 2) and immediately after unloading (Sample 3) from 13 horses shipped from Houston to Amsterdam (test-group) and from 6 horses shipped from Amsterdam to New York (control-group) for complete routine screening. Prior to loading both groups had a 5 h resting period at the airport. Before and during the flights ambient air temperature (AT) and relative humidity (RH) were measured in each jet-stall.


The AT for the test-group from loading until take off was 35.3 ± 1.89°C (max. 41.1°C) and RH 41%. For the control-group AT was 18.2 ± 2.1°C (max. 21.1°C) and RH 65%. From take off to arrival AT and RH for the test-group were 23.3 ± 3.0°C and 28%, and for the control-group 20.6° ± 1.4°C and 40%, respectively. Samples 1, 2 and 3 showed in the test-group higher (P<0.05) urea concentration (4.87 ± 1.06, 5.22 ± 1.06 and 5.06 ± 1.13 mmol/l) and lymphocyte count (3.85 ± 1.06, 3.48 ± 1.55 and 3.20 ± 2.12 109/l) than in the control-group (3.68 ± 0.53, 4.12 ± 0.59, 4.25 ± 0.58 and 1.95 ± 0.72, 1.97 ± 0.68, 1.83 ± 0.56). In the test-group lactate concentrations (mmol/l) were significantly higher in Samples 1 and 2 (test-group 1.53 ± 0.35 and 1.84 ± 0.51; control-group 1.15 ± 0.83 and 1.35 ± 0.40), and creatinine kinase (iu/l) was higher in Sample 1 (test-group 326.0 ± 123.04; control-group 201.2 ± 69.5).

Conclusions and practical significance

Earlier studies proved that air transport is less stressful than road transport. This study demonstrates that high AT with moderate RH prior to take off resulted in significant elevation of some blood parameters. These findings support an increased susceptibility to illness, e.g. shipping-fever in horses after long-distance flights from hot and humid places.

Ethical animal research

Approved by the Ethical Committion of KLM Cargo. Horse owners gave consent for blood sampling. Sources of funding: Team Amstelstreek, Ronde Hoep, the Netherlands; Air France-KLM-Martinair Cargo; G. Klatte, Germany. Competing interests: None.