Sleep Pattern Interference in the Cognitive Performance of Lusitano Horses

Simple Summary Little is known about how incomplete sleep affects a horse's memorization. Like most mammals, horses need sleep to fully function, with differences in the total sleep time needed. The literature shows that horses need about three to four hours divided between two phases: the REM (rapid eye movement) phase and the NREM (non-rapid eye movement) phase. The aim of this study was to better understand how interference with the REM phase can affect the memory skill of horses. For this study, 10 horses were filmed in their stall to characterize their sleep patterns for 48 h. Afterwards, horses that experienced REM sleep interference and horses that did not experience REM sleep interference (control) over 72 h were evaluated by performing a spatial memory test and a visual attention test. A time period of 48 h seemed long enough to characterize the individual sleep patterns of the horses. REM sleep deprivation appeared to increase the response time of the horses in spatial memory tasks. This study shows the importance of preserving sleep patterns in horses, and, with further studies, the results could be used to improve welfare conditions for horses.Abstract Like most mammalian, polyphasic sleep, equine sleep can be divided into two phases: the REM (rapid eye movement) phase and the NREM (non-rapid eye movement) phase. For this study, a randomized crossover experiment was conducted using ten purebred Lusitano horses, all dressage athletes aged from three to seven years old. The horses were filmed before the intervention to characterize their sleep patterns. REM sleep deprivation was achieved by not letting the horses attain sternal or lateral recumbency for three consecutive days, totaling 72 h. A spatial memory task and a visual attention test were performed. A recording time of 48 h appeared to be long enough to characterize the sleep patterns of the stalled horses. The total recumbency time of the studied population was lower than that previously reported in horses. Although the recumbency times before and after the intervention were similar, there was a tendency shown by the delta (p = 0.0839) towards an increased time needed to resolve spatial memory tasks in the sleep-deprived group. Future studies may deepen the understanding of horse sleep requirements and patterns, and the effects of environmental changes on horse sleep.