Not sure if this might interest you or not, but on another site I was reading about horses that are just standing one minute and then falling over. Here is what one vet posted, I'll ad her website as well.
www.drdrock.com Might be worth looking into other options for this horse.
Sleep Deprivation is Not Narcolepsy in Horses (EQ29)
Western Veterinary Conference 2012
Joseph J. Bertone, DVM, MS, DACVIM (LAIM)
College of Veterinary Medicine, Western University of Health Sciences,
Pomona, CA, USA
24026243Figure 1. A chronically sleep-deprived horse
On the left, he is diffusely drowsy. Rather than arousing and lying down, he ends in the position on the right for a few seconds and then wakes to cycle
over and over again. He will not lie down.
Narcolepsy With or Without Cataplexy and Sleep Deprivation
Narcolepsy/cataplexy is extremely rare and breed-specific.1 In this author's opinion, sleep deprivation and subsequent deficiencies in paroxysmal and
hence recumbent sleep are far more common and also commonly misdiagnosed as narcolepsy. Narcolepsy is associated with excessive sleepiness and
pathologic manifestations of Rapid Eye Movement sleep (REM), which occurs in periods of paradoxical sleep and includes loss of motor function.
Excessive Drowsiness Secondary to Recumbent Sleep Deprivation
Horses need a period of recumbent sleep that can be avoided for several days
but eventually must be taken.2 Recumbent sleep deprivation is manifested as diffuse drowsiness that moves to early slow wave sleep. Partial collapse
follows with sudden arousal. However, instead of lying down, the cycle
repeats itself. The author places cases of excessive drowsiness into 4 categories.
1. Pain-associated excessive drowsiness is defined as those cases where
horses do not lie down because it is painful to do so, or it is painful to
rise or both. Most often these horses have musculoskeletal issues that
create pain or mechanical difficulties on attempts at recumbency or rising
to stand or both. Horses can also have episodes with thoracic or abdominal
pain that is elicited with recumbency or on attempting to stand.
2. Environmental insecurity-associated excessive drowsiness is the
condition where horses do not lie down because they are psychologically uncomfortable doing so, because horses will only lie down when they are environmentally comfortable.4 One can assume that this stems from horses as
prey and herd behavior. The author has managed several horses with this
syndrome by adding a friend (especially adding a mare) to the pasture or
stall, or moving the horse to an area where there are more horses, or
removing an aggressive horse from a group where several horses may have the problem. This would also include horses in an insecure environment that may
just require a larger stall or paddock, or those horses near loud harassing noise, like fireworks or speedways.
3. Monotony-induced excessive drowsiness is best exemplified by the horse
in crossties being braided, that begins to lower its head to the point of
near collapse. This is assumed to be the horse moving from slow wave to paradoxical sleep.4 This may also be seen more commonly at the odd hours
that owners tend to braid horses. The horse is often very comfortable in its environment and near sleep is simply induced.
4. Dominance displacement excessive drowsiness is the condition where a
gelding acts as a constant dominant mare until a true dominant mare is
placed into the herd. These horses are often seen as aggressive toward other horses. Episodes begin when the horse is stalled or otherwise removed from
the herd.
Sleep
Sleep, patterns of sleep, and sleep behavior are, in general, not areas of concern in veterinary medicine. There is a traditional lack of concern with sleep and its impact on performance and clinical outcome. That is difficult
to understand in light of the need for sleep's essential, sustaining, recuperative physiology in other species. Sleep is commonly defined as a
period of immobility in which individuals seem unresponsive to their environment. Sleep now is accepted as a behavior with clear physiologic necessities that are not understood, but when lacking have clear
dysfunctional impact. As a component of the day, it is estimated that horses require 2 hours of drowsiness, 3 hours of slow wave sleep, less than 1 hour
of paradoxical sleep, with 4 hours of total sleep time.4 There is no
definitive explanation for the necessity or the function of sleep in horses,
or for that matter in all other species.
Influences on Sleep
Sleep can be altered by environmental and physical factors. Horses assume recumbency in a comfortable environment. When moved to an uncomfortable environment, sleep can be adversely affected for several days. When subjects
are put outdoors, it may be 1 or 2 days before they first lie down.4 This habituation may be socially facilitated. If 1 horse is familiar with the new environment, it will lie down and the others will follow. It is felt that
the dominant animal is usually the first to lie down.3 Observing wild ponies indicated that recumbent resting behavior occupies 16% of a horse's time.
This behavior reaches a peak between 12:00 a.m. To 4:00 a.m. All ponies were never seen to be lying down simultaneously.4 However, this contrasts with a study with feral Appaloosa horses, where the entire herd was seen recumbent
at one time during each day.5
Summary
In the 20-year collection of cases of sleep deprivation, it has been unusual
to manage a case with drugs, other than pain relief. An understanding of
sleep, sleep deprivation, and narcolepsy makes for a clearer, more
successful diagnosis and management plan.
References
1. Lunn DP, Cuddon PA, Shaftoe S, Archer RM. Familial occurrence of
narcolepsy in miniature horses. Equine Vet J. 1993;25(6):476–477.
2. Dallaire A. Rest behavior. Vet Clin N Am Equine Pract. 1986;2(3):591–607
3. Ruckebusch Y. The relevance of drowsiness in the circadian cycle of farm animals. Anim Behav. 1972;20:637–643.
4. Keiper RR, Keenan MA. Nocturnal activity patterns of feral ponies. J
Mammal. 1980;61(1):116–118.
5. Stebbins MC. Social organization in free-ranging Appaloosa horses. Unpublished M.S. thesis. Pocatello, Idaho State University; 1974.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by
this speaker)
Joe J. Bertone, DVM, MS, DACVIM (LAIM)
College of Veterinary Medicine, Western University of Health Sciences
Pomona, CA, USA
