STRESS RESPONSES OF HORSES DURING A LONG-PERIOD OF TRANSPORT IN A COMMERCIAL TRUCK

Objectives-To characterize progressive patterns of dehydration, stress responses, and water consumption in horses transported long distances in hot weather and to evaluate various measurements in detecting dehy dration and stress in transported horses. Design-Prospective study. An imals-30 mature, healthy horses. Procedure-The following 4 treatment g roups were studied: horses that were penned and offered water every 5 hours (n = 5), horses that were penned and not offered water (5), hors es that were transported in a truck and offered water every 5 hours (1 0), and horses that were transported and not offered water (10). The s tudy commenced after 6 hours of water deprivation. Every 4 hours, the truck returned to the pen area and body weights were measured, physica l examinations were performed, and blood samples were obtained. During this 1-hour period, water was offered to some horses, depending on tr eatment group. Results-After 24 hours of transport, 3 horses were judg ed unable to continue and the study was terminated. Horses that were p enned and offered water drank a mean of 38.2 L and horses that were tr ansported and offered water drank 20.9 L, but some of the latter horse s did not drink until after 19 or 24 hours of transport. In horses tha t were transported or penned and not offered water, serum electrolyte concentrations were greater than reference range values by 19 hours. M ost horses that were transported and offered water consumed adequate w ater to postpone severe dehydration beyond 24 hours. Clinical Implicat ions-Tame horses in good condition and initially deprived of access of water for approximately 6 hours can be transported in groups in open trailers during hot, humid conditions for up to 24 hours before dehydr ation and fatigue become severe. Rectal temperature and appearance of the horses were the most useful measures for determining crisis situat ions.