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.

Rest and sleep are key components of equine welfare and athletic performance, particularly in young racehorses adapting to the demands of early training. This preliminary study evaluated resting behavior in five two-year-old Thoroughbreds during their initial adaptation to stabling and after their first high-intensity gallop. Horses were monitored using continuous 24-hour infrared video recordings at two time points: immediately following arrival at the racetrack (M0) and approximately 3–4 months later, during advanced training (M1). The total time spent standing, in sternal recumbency, and in lateral recumbency, as well as the frequency of recumbent events, were quantified. No day-to-day differences were detected within either moment. When comparing moments, horses spent significantly more time standing (P = 0.003) and less time in both sternal (P = 0.017) and lateral (P = 0.049) recumbency at M1. Lateral recumbency frequency was reduced following intense exercise (P = 0.003) when compared to M0, whereas no other exercise-related effects were identified. In conclusion, despite the progressive increase in workload, the horses did not exhibit major disturbances; however, further research is needed to clarify whether these behavioral changes represent adaptation, vigilance, or early indicators of sleep restriction.

Asthma is a chronic respiratory disease that can occur in horses of different breeds and ages. While its occurrence has been reported in many countries, its occurrence across Brazil is unclear. This review aimed to gather information about equine asthma from studies performed in Brazil by different groups and investigate a variety of horse populations. Articles published in peer-reviewed scientific journals, as well as information contained in dissertations and theses, were searched on PubMed, SciELO, Google Scholar, and the Brazilian government catalog of dissertations and theses. Fifteen studies were included in this review, and according to the published information, the authors identified equine asthma using clinical signs, endoscopic findings, and/or cytological examination of tracheal wash and/or bronchoalveolar lavage fluid. Studies have investigated horses of different breeds and activities (racehorses, police horses, riding horses, Crioulos horses, and others) and were performed in different regions with diverse climatic conditions. On the previous observed studies, the occurrence varied from 14.0% to 60.0%, with a mean occurrence of 24% for severe asthma. Other studies must be performed to further understand the occurrence of equine asthma in Brazil, according to different climatic regions.

Relation between exercise-induced pulmonary hemorrhage and findings in upper airway and trachea in Thoroughbred racehorses

The present study aimed to describe and compare the electroencephalographic patterns of sleep in horses during recumbent and standing positions, identifying the cortical dynamics and spectral characteristics associated with each stage. Eight clinically healthy adult horses were monitored through polysomnographic EEG recordings, using a double-banana montage with subcutaneous needle electrodes. Sleep stages were classified according to spectral and morphological criteria analogous to human scoring standards, with one sleep cycle analyzed per horse. REM sleep was posture-dependent, with complete paradoxical patterns observed only in recumbent horses. In standing animals, a REM-like state was identified, marked by rapid eye movements but cortical hypoactivation and absence of muscle atonia. Quantitative analysis revealed that N1 and N2 accounted for approximately 90% of total sleep duration, while N3 and REM represented smaller fractions. Standing horses exhibited longer light sleep stages and a smaller proportion of N3 sleep. These findings demonstrate that equine sleep architecture is highly posture-dependent, and behavioral postures such as sternal or lateral recumbency cannot be reliably used as proxies for specific EEG sleep stages. The study provides a methodological framework to support future investigations and facilitate comparisons of equine sleep physiology across studies and species.