Effects of density and water availability on the behavior, physiology, and weight loss of slaughter horses during transport

The aim of this study was to determine the effects of density and provision of water on behavior, stress, and weight loss in slaughter horses during transport. A 16.2-m long, single deck, semi-trailer was divided into three compartments to create high, medium, and low density (5000, 4000, and 3000 kg per compartment, respectively) groups of slaughter horses. A total of six shipments containing 23 to 30 horses per shipment were transported in June and July of 2004 for 18 to 20 h. Horses were a variety of different breeds, ages, sexes, and body conditions, but were typical of slaughter horses. Jugular blood samples were taken from five horses in each of the three density treatments immediately before loading and after unloading at the completion of each shipment. All horses were weighed at the same time as the blood samples were collected. While the truck was stopped, horses in each of two compartments received water from three automatic water bowls in each side of a compartment. The water was provided for 1-h after 8 h of transport and then again just prior to unloading. The third, non-watered compartment served as a control for each of the 1-h watering sessions. Densities selected to receive water were alternated between shipments. The aggressive behavior of the horses for the six shipments was recorded using 12 video cameras installed in the trailer. All occurrences of aggressive behavior were counted from 15-min segments of video during 2-h intervals for each horse that was visible in each density group. Density did not significantly affect (P > 0.21) aggressive behavior, cortisol, serum chemistry profile, dehydration, and weight loss. Aggression level did not differ (P = 0.49) between the first and second halves of the shipments. Individual horses, rather than density, appeared to be the cause of aggressive behavior. The watered and non-watered groups did not differ (P > 0.54) in terms of aggression, cortisol, serum chemistry profile, dehydration, and weight loss. Density and provision of water did not significantly influence aggressive behavior, stress and weight loss in shipments of 18 to 20 h long during warm weather.