Effect of loading into a truck, short isolation and unloading on packet cell volume (PCV), behavior and physiological parameters in Quarter Horses

A proliferation of literature has investigated the effect of road transport in farm animals (Stockman et al., 2013). In horses loading is a critical point of transportation, often causing injures both to horses or owners and wasting time (Ferguson and Rosalez Luis, 2001). Loading is considered a mental stress in horses (Waran and Cuddeford, 1995). Horses have to leave a familiar environment and herd. They often have a negative association with the truck: a long period of isolation, no possibility of escape, and racing or competition after unloading (Slater and Dymond, 2011). Studies on transport stress are adequate but those about only loading procedures are few and need replication (Shanahan, 2003). The aim of this work was to investigate the effects that loading, short isolation in the truck and unloading without a travel experience had on physiological and behavioral parameters after many repetitions. Fourteen Quarter Horses, accustomed to travel, homogeneous for live weight (500 ± 25 kg), body condition score (3 ± 0.25 arbitrary units; Martin-Rosset, 1990) and age (6 ± 1 years), were recruited in this study. Each animal was loaded into the truck, without any reinforcements or punishments, spent one minute inside (tied parallel to the direction of travel), unloaded and returned to its box stall. The experiment was repeated 12 times. All animals were tested on the same day once weekly over 12 weeks. The horses were examined at rest in their stalls (Time I), after loading (Time II) and after unloading (Time III). Each examination included the registration of heart rate (HR) by Heart Monitor (Polar) and respiratory rate (RR) by the observation of chest-wall movements. At Time I and III blood samples were collected by venopuncture to assess cortisol level, PCV and total protein. All phases were recorded by video camera to score the horse behavior. A group of ten persons marked the horses during loading, isolation and unloading applying a behavioral score (BS) from 1 (relaxed) to 5 (refusal to load). Maximal time for loading was set at 5 minutes.. General Linear Model analysis for repeated measures revealed differences in the HR and RR over the experimental period and in PCV and cortisol between rest and after unloading (Table 1). The BS was also significantly different among the different transport phases (loading (1.96±1.35) and unloading (1.79±0.78) vs short isolation (1.38±0.56); F=12.91; P<0.001). Our data confirmed that horses were under stress by loading into a truck. They released adrenaline that caused the significant increase of HR, RR and PCV. Cortisol level also showed an upward trend, which is typical after a stressful situation. We suggest that loading into the truck is still a fearful experience after 12 repetitions, so this event requires appropriate management even in horses well trained and accustomed to transport. Further studies are needed in this field to develop new methods of loading procedure to reduce stress and safeguard horses’ welfare.