Weaving, Headshaking and Cribbing (AAEP Convention 2005)
We often punish horses for exhibiting undesirable stereotypic behaviors, but most of these behaviors are responses to suboptimal environments. Thus, punishing the horse for the behavior only increases the already heightened stress that caused the behavior. This is why so many cases do not respond to these treatments, explained Daniel Mills, BVSc, PhD, CBiol, MIBiol, ILTM, MRCVS, Professor of Behavioural Medicine at the University of Lincoln, United Kingdom. He discussed various behaviors at the 2005 American Association of Equine Practitioners Convention held Dec. 3-7 in Seattle, Wash.
"These efforts at control can reach quite remarkable levels of cruelty, but this almost always reflects the owner's misunderstanding of the nature of the behavior rather than any ill intent on their part," said Mills. Instead, he recommended changing management strategies to remove the cause(s) of the behavior, or allowing the horse to continue the behavior in a safer manner (such as by providing rubber cribbing boards that don't splinter or damage the horse's teeth), rather than using punishing methods for control.
But to change the management or remove the cause of the behavior, first we must understand what caused the behavior and why. Mills reviewed scores of studies on stereotypic behaviors to shed light on general risk factors for weaving, box-walking, cribbing, wood-chewing, and headshaking.
General Risk Factors
Genetic factors--"Behavior is neither purely learned nor purely genetic, but a combination of both," said Mills. "However, it must be recognized that it is not the behavior that is inherited, but the tendency to perform the behavior."
Diet/feeding practices--While many studies have found associations between feeding practices and stereotypies, Mills said this relationship is not simple, since feeding practices also include such factors as time spent feeding that can exert their own influences. "Generalizations about the effect of diet on these behaviors as a whole are generally unwise," he said.
Social influences--While it is often said that other horses will learn a stereotypy such as cribbing from a horse performing the behavior, Mills said evidence for this is at best poor and in general absent.
Other factors--Weaning stress, having a dominant mare for a dam, and time when started under saddle seem to be important triggers for stereotypies, noted Mills.
At an incidence of only about 3% of the population for weaving and about 2% for stall walking, these two behaviors might seem pretty insignificant. But they indicate a response to stress in affected horses' environments. Mills reported that some studies have found a greater incidence of these behaviors in Arabians, and that the age of onset tends to be much later (60-64 weeks) than cribbing (20 weeks).
Mills described the following typical presentation for a weaver:
- Weaving often precedes an arousing event (i.e., feeding).
- Close social contact is restricted, but the horse might have visual access to other horses across the walkway.
- Exercise requirement and daily food allowance are not properly matched.
- The management routine is highly predictable.
- The bedding is something other than straw.
- There is no lameness apparent.
How can weaving be reduced? "Standing stalls are associated with a lower prevalence of weaving than isolation stalls," said Mills. "Weaving is also less common on larger facilities (more than 75 horses) where horses are fed a forage other than hay, such as silage, etc., where more forage is fed, where horses have visual and tactile contact with con-specifics (other horses), and where horses are bedded on straw. Not only can increasing social contact reduce weaving, but this effect can be replicated with mirrors." (For more information on using a mirror to combat stereotypies, see www.TheHorse.com/5644.)
He also noted that insufficient exercise and decreased amounts of turnout (as in winter) could contribute to weaving and stall walking. He offered the following treatment recommendations:
- Increase turn-out and exercise.
- Match exercise and turn-out with sporting requirements.
- Use feeding stations around the stall or scatter feed around the stall.
- Try to reduce predictors of the arrival of food. Consider using a range of foraging toys (such as a feed ball) with variable amounts of concentrate in them if concentrate feeding is necessary, but beware--it will make some horses more frustrated and it might increase other undesirable behaviors such as door kicking.
- Introduce a stall mirror if the horse is sociable.
- Avoid using anti-weaving grills and drugs.
He also presented the following preventive measures:
- Manage from pasture as much as possible (try to keep the horse at pasture rather than stalled).
- Consider the potential for social housing.
- Wean gradually rather than abruptly, and wean in groups or with a mirror companion.
"Sensitive management should consider reducing cues and routines that could cause an expectation of feeding or exercise while allowing adequate exercise, feed, and social interaction in a controlled setting," Mills summarized.
Mills said the incidence of cribbing has been estimated at up to 10.5% in some populations of horses. And although many say that cribbing causes colic because of air swallowing, he reported that there is little to no air swallowing as indicated by fluoroscopy. Thus, with the proven exception of epiploic foramen entrapment (see www.TheHorse.com/4932), this is an illogical cause of colic. However, he said that physical causes of cribbing, such as possibly gastric ulcers and other gastrointestinal problems, might contribute to colic as well.
He also gave this summary of cribber characteristics:
- Characteristic behavior with oropharyngeal grunt (from the throat and back of the mouth).
- History of intermittent colic.
- Evident wear of the labial surface of the upper incisors (nearest the horse's lips).
- Difficulty in maintaining weight.
- Restlessness in the stable.
- Hypertrophy (enlargement) of the ventral neck muscles.
- Gastric ulceration.
- Lower than normal fecal pH.
- Greater activity at rest in the part of the nervous system associated with action and stress.
- In cases of field cribbers, the fence planks and posts might be worn.
For correcting cribbing, Mills said, "Given that the behaviors may have some adaptive valueï¿½it is preferable to allow the animal to continue to perform the behavior on a suitable substrate (such as an old car tire) than to simply prevent the behavior."
He also noted that stomach inflammation/ulceration are often implicated, and that antacid treatment helps some horses, particularly in decreasing cribbing after feeding. However, the behavior might become well-established and persist after any physical cause is gone.
Mills presented the following recommendations to treat cribbing:
- Carefully examine and treat any underlying visceral pain, especially gastric ulcers.
- Reduce concentrate and sweet feed to a minimum or supplement with an antacid; if concentrates are essential, fat- or oil-based rations are preferable to carbohydrate-based ones.
- Increase forage and turnout on pasture.
- Provide cribbing boards rather than using anti-cribbing collars.
- Consider surgery as a last resort when there is a clear and serious risk to the animalï¿½s health if the behavior is allowed to continue.
- Avoid creep pre-weaning.
- Manage the horse on pasture as much as possible.
This behavior occurs in up to one-third of some populations, and it is seen more often in horses on low-fiber diets, Mills reported. While there seems to be an association between wood chewing and cribbing, this is not a simple association, he said. Like cribbing, this oral stereotypy seems to have its roots in physical discomfort ranging from hunger to severe pain.
"Horses with a headshaking problem typically present with recurrent, intermittent, sudden, and apparently involuntary bouts of head tossing that may be so extreme as to throw the horse and rider off balance," said Mills. "The headshaking is frequently accompanied by sneezing or snorting and attempts by the horse to rub its nose on the ground, on a foreleg, or on nearby objects."
The condition can appear at any age, although it usually arises at about five years of age. Diagnosis and treatment are often difficult, as a specific physical cause is rarely found. No fewer than 58 causes have been proposed, including a response to bright sunlight, allergies, trigeminal nerve pain, overzealous bit seats (rounding of the first upper and lower cheek teeth to accommodate a bit), and airway turbulence. Treatments include bitless bridles, nose nets to decrease airway turbulence, homeopathy, and herbal supplements.
"The range of treatments that seem to have a significant effect is notable," he said. "This could also be interpreted to provide further evidence of the importance of trigeminal neuralgia in the condition, because in humans, unpredictable and intermittent remission is a common finding." Improvement concurrent with treatment, whether relief is provided by the treatment or not, is often interpreted as treatment success.
"There are almost no decent controlled studies on headshaking, so we have no confidence in how effective these treatments are," Mills said.
"These problems do need to be taken seriously; they are a major welfare concern," Mills summed up. "They cause lots of pain and frustration.
"Repetitive behaviors are multi-factorial, arising from a combination of environmental and genetic risk factors in a given individual at a given time," he added. "Prevention should aim to reduce these risk factors."
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.
POLL: University Equine Hospitals