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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Repetitive, apparently functionless behavior that may be considered to be compulsive
  • The predominant oral stereotypy is cribbing (grasping a horizontal surface with the incisors, flexing the neck, and making a grunting sound)

Pathophysiology!!navigator!!

  • Cribbing is the only stereotypy in which the pathophysiologic mechanism has been elucidated with endoscopy and fluoroscopy. Air is usually not completely swallowed, but stays in the upper esophagus causing transient dilation. The grunting noise is produced when air rushes through the cricopharynx. Contraction of the ventral neck muscles produces negative pressure in the esophagus that allows air to move in; the air then is expelled from the pharynx rostrally, with only a small amount passing into the lower esophagus
  • Endogenous opiates may be involved, because administration of an opiate blocker inhibits cribbing for several hours. Cribbing does not cause release of endogenous opiates and measurement of opiates in cribbers in comparison with noncribbers has yielded contradictory results, but opiates are necessary for cribbing to occur
  • Young horses that crib have more severe gastric ulcers that those that do not crib; therefore cribbing may cause ulcers due to vagally stimulated gastric acid secretion resulting from either the chewing movements or stimulation of the lips and mouth

Systems Affected!!navigator!!

GI, Neurologic, and Musculoskeletal

  • Behavioral cribbing is repetitive, apparently functionless behavior involving the head. Some horses exhibit gas colic and a few suffer from epiploic foramen entrapment. Tooth grinding can lead to wear of the molars. Wear of the upper incisors is another outcome of cribbing, as is temporomandibular arthropathy
  • Affected horses may have an increased incidence of colic, and possibly an increased risk of developing an entrapment of the small intestine in the epiploic foramen
  • A greater percentage of horses with neurologic problems such as equine motor neuron disease seems to be affected
  • Musculoskeletal thickening of the neck muscles can be a cosmetic problem

Genetics!!navigator!!

There is a definite breed predilection; Thoroughbreds are the most affected.

Incidence/Prevalence!!navigator!!

The prevalence of cribbing is approximately 4%. The mortality rate is unknown.

Geographic Distribution!!navigator!!

Cribbing has been observed worldwide.

Signalment!!navigator!!

Usually an adult horse confined in a stall, fed a high-concentrate diet, and used for activities such as flat racing, jumping, 3 day eventing, or dressage.

Breed Predilections

Thoroughbreds have a higher risk of cribbing. Standardbreds have a very low incidence.

Mean Age and Range

The age of onset is at weaning and the frequency of diagnosis increases with age.

Predominant Sex

Males are more likely to crib, especially young horses. Older mares are more likely to crib than old geldings or stallions.

Signs!!navigator!!

General Comments

Cribbing—the horse grasps a horizontal surface with its incisors, flexes its neck, and allows air to pass into the upper esophagus. A few horses do not grasp a horizontal surface, but flex their neck and make a grunting sound. These are called wind suckers.

Historical Findings

Stereotypic behavior usually begins with an abrupt change in the environment; e.g. taking a horse from pasture and immediately limiting its access to hay can be the initiating factor to cribbing.

Physical Examination Findings

Well-developed neck muscles and wear of the upper incisors with cribbing. Occasionally a horse is very thin because it spends so much time cribbing that it does not have time to ingest the calories it needs.

Causes!!navigator!!

  • The cause of stereotypic behavior is unknown
  • Boredom probably is not a cause, because providing stall toys usually does not help and an increase in exercise increases time spent cribbing
  • The horse is thwarted in some goal, usually grazing, and the frustration leads to repetition of a behavior that is part of the appetitive portion of that behavior (e.g. cribbing as part of biting a mouthful of grass as the first step of ingestion)
  • Feeding sweet feed or other highly palatable food stimulates cribbing

Risk Factors!!navigator!!

  • Genetic predisposition for Thoroughbreds
  • Stall confinement with limited (<7 kg) forage, <40 L/day of water, bedding other than straw, and minimal visual or tactile contact with other horses
  • Race, dressage, jumping, and eventing horses are at greater risk than endurance horses
  • In only 10% of cases has another horse begun to crib after a cribber arrived in the barn or pasture. There is little evidence that horses learn to crib by observing other horses; however, if a horse has a genetic predisposition to crib and is in an environment conducive to cribbing with other cribbers, it may acquire the behavior without observational learning having occurred

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Differentiate cribbing from wood chewing. The cribbing horse grasps wooden edges but does not ingest them; the wood-chewing horse does. The cribbing horse makes a loud noise when the air passes through the pharynx; the only sound made by the wood-chewing horse is that of wood being splintered.

CBC/Biochemistry/Urinalysis!!navigator!!

Perform a physical examination, chemistry screen, and CBC to determine the presence of an underlying disease and to judge whether medication can be administered safely.

Other Laboratory Tests!!navigator!!

N/A

Imaging!!navigator!!

Endoscopic examination should be performed to rule out GI tract problems as a cause of cribbing.

Other Diagnostic Procedures!!navigator!!

Endoscopy and to determine if ulcers are present.

Treatment ⬆ ⬇

Outline

TREATMENT

Aims!!navigator!!

The aims are to decrease the horse's motivation to crib or engage in other stereotypies. The secondary aim is to prevent GI problems that are associated with oral stereotypies.

  • Diet change has the most impact, especially in horses that have just begun to crib. Feeding a hay diet with another source of forage and no sweet feed results in the lowest rate of cribbing. Substitution of fat (e.g. corn oil) for carbohydrates (e.g. molasses and grain) can be done for horses that expend more calories than hay provides
  • Other treatments are aimed at creating a normal equine environment, which means the horse has physical contact with other horses and available forage at all times. The best environment for the horse is to remove it from the stall and put it in a compatible social group with access to pasture or hay free choice. When the use of the horse precludes keeping it in a group with a run-out housing situation, eliminating risk factors (e.g. limited forage, wood shavings as bedding) helps. Stall toys generally are ineffective as are taste repellents. Punishment is not the preferred method of treatment, but clinicians should be aware of this option. Several types of collars (wide leather straps, a nutcracker or metal collar, or one on a headstall to prevent slipping) can pinch the horse when it cribs or mechanically prevent neck flexion. A metal muzzle prevents the horse from making contact with a horizontal surface
  • Provide oral stimulation in the form of several types of forage, pasture, or a barrel the horse can turn to receive pelleted feed or grain. If the behavior occurs before feeding, the horse probably is frustrated by hunger (i.e. undernourishment); if it occurs after feeding, the horse probably is frustrated from the lack of a specific dietary component (i.e. malnourishment)

Appropriate Health Care!!navigator!!

Outpatient care should be sufficient.

Nursing Care!!navigator!!

NA

Activity!!navigator!!

Forced exercise may increase cribbing behavior.

Diet!!navigator!!

The diet should be high in roughage and low in carbohydrates and grains other than oats.

Client Education!!navigator!!

The owners should be told that cribbing is not a “vice” but rather a response to the unnatural environment in which we keep horses. Managers of broodmares should know that weaning on pasture greatly reduces the risk of the foal beginning to crib.

Surgical Considerations!!navigator!!

Accessory neurectomy and strap muscle myectomy can be performed. Reserve these surgical approaches for horses that experience colic when they crib or are emaciated because they crib rather than eat. The side effect is that a stomach tube cannot be passed through the stricture created by the myectomies

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Opiate blockers such as naloxone (0.02–0.04 mg/kg IV), naltrexone (0.04 mg/kg SC), or nalmefene (0.08 mg/kg IM) inhibit cribbing, but these drugs are too expensive and too short acting to be practical. IV dextromethorphan 1 mg/kg has been used to reduce cribbing.

Contraindications!!navigator!!

Mares during late pregnancy.

Precautions!!navigator!!

GI side effects, including diarrhea, inappetence, and behaviors indicative of colic, are seen after naloxone administration.

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

Acupuncture

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

Regular follow-up after 2 weeks of treatment to evaluate the owner's compliance and the success of the treatments given.

Possible Complications!!navigator!!

N/A

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

Usually a disease of mature horses.

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

  • Crib biting
  • Wind sucking

Abbreviations!!navigator!!

GI = gastrointestinal

Suggested Reading ⬆ ⬇

Albright JD, Mohammed HO, Heleski CR, et al. Crib-biting in US horses: breed predispositions and owner perceptions of aetiology. Equine Vet J 2009;41:455–458.

Albright JD, Witte TH, Rohrbach BW, et al. Efficacy and effects of various anti-crib devices on behaviour and physiology of crib-biting horses. Equine Vet J 2015;48(6):727–731.

Archer DC, Pinchbeck GK, French NP, Proudman CJ. Risk factors for epiploic foramen entrapment colic: an international study. Equine Vet J 2008;40:224–230.

Delacalle J, Burba DJ, Tetens J, Moore RM. Nd:YAG laser-assisted modified Forssell's procedure for treatment of cribbing (crib-biting) in horses. Vet Surg 2002;31:111–116.

McGreevy PD, Richardson JD, Nicol CJ, Lane JG. Radiographic and endoscopic study of horses performing an oral based stereotypy. Equine Vet J 1995;27:92–95.

Rendon RA, Shuster L, Dodman NH. The effect of the NMDA receptor blocker, dextromethorphan, on cribbing in horses. Pharmacol Biochem Behav 2001;68:49–51.

Whisher L, Raum M, Pina L, et al. Effects of environmental factors on cribbing activity by horses. Appl Anim Behav Sci 2011;135:63–69.

Wickens CL, McCall CA, Bursian S, et al. Assessment of gastric ulceration and gastrin response in horses with history of crib-biting. Equine Vet J 2013;33(9):739–745.

Author(s) ⬆

Author: Katherine Albro Houpt

Consulting Editor: Victoria L. Voith