Effects of different LED lighting conditions on young horses during trailer loading and stationary confinement

Transporting horses, particularly during the loading phase, is known to be stressful and dangerous, especially for younger horses. Different factors help create a reluctance to enter a trailer, including internal and external lighting conditions. The aim of this study was to investigate how LED lighting affected the loading and stationary phases of transporting horses and the impact this had on behavioural and physiological parameters. Specific moveable white LED lighting fixtures were positioned on the ceiling of a two-stall rear trailer with diffused homogeneous lighting. Twenty young trotter horses, in their early stages of training (with little experience of loading and travelling), were loaded three times into the trailer following a standardized protocol (Loading Phase) and stayed in the stationary trailer for two minutes with the experimenter (Stationary Phase). For each loading trial horses were divided into two groups and each group was tested in three different lighting conditions: Group One: neutral white light 4500 K (Luminous flux=100 %), neutral white light 4500 K (Luminous flux=50 %) and natural lighting which changed throughout the day; Group Two: warm white light 3000 K (Luminous flux=100 %), cold white light 6300 K (Luminous flux=100 %) and natural lighting which changed throughout the day. Each loading trial was assigned randomly to each horse within his group and took place every 20 ± 2 days. During the Loading Phase and the Stationary Phase, stress-related and investigative behaviours did not differ significantly between the conditions in each group. Moreover, the colour temperature (warm or cold) during the Stationary Phase had a positive influence on the horse’s heart rate recovery when the horse returned to their stable. When the first loading trial was studied regardless of the initial lighting conditions, it appeared that horses loaded into the trailer with a high illuminance level inside the trailer (>4500 lx) took significantly less time to approach the trailer. They expressed significantly less stress-related behaviours during the Loading Phase than those loaded when the illuminance level (