Category: Glossary

To ingest is to take a substance into the body by swallowing it through the mouth. In horses, ingestion is the primary route by which feed, water, oral medications, supplements, and environmental toxins enter the digestive system. Once a substance is ingested, it passes through the intestinal absorption downstream for absorption or excretion. The rate and completeness of ingestion influence drug bioavailability, caloric uptake, and toxic load.

Horses that ingest sand or soil while grazing on sparse sand and toxin ingestion from pasture accumulate abrasive material in the ventral colon, a leading cause of sand colic. Voluntary feed ingestion slows during illness, dental pain (see dental pain slowing feed intake), or high ambient temperature; monitoring daily dry-matter intake is therefore a core husbandry practice. Involuntary ingestion of toxic plants is a common emergency scenario requiring immediate veterinary assessment.

Further Reading

The biological process of ingestion is explained in the ingestion article on Wikipedia. How ingestion relates to equine digestive health is addressed in the Merck Veterinary Manual section on Digestive Disorders of Horses.

Discharge is any substance, fluid, pus, mucus, blood, or exudate, that flows or oozes from a wound, lesion, or body opening. In equine medicine, discharge is a clinical sign evaluated by character (clear, cloudy, purulent), color (white, yellow, green, red, brown), consistency (watery, thick, mucoid), and location. The combination of these features points toward the underlying cause and guides the urgency of veterinary attention.

Common locations and their significance: nasal discharge is normal in small clear amounts; bilateral mucopurulent (yellow-green, from both nostrils) discharge suggests respiratory infection or strangles. Ocular (eye) discharge that is clear and minimal is common with dust or irritants; thick or purulent ocular discharge indicates infection. Discharge from a wound indicates the wound is producing exudate, clear or slightly pink serous fluid is normal in early healing, while purulent (pus-containing) discharge indicates bacterial infection. Discharge from the hoof, particularly in the coronary band area or from the sole, is a classic sign of abscess drainage as a common source.

The depth of dermal involvement context matters: discharge that originates from a wound or lesion that has not penetrated to living tissue is an epidermal issue; discharge from a wound reaching the dermis or deeper signals live-tissue involvement with greater infection risk. In all cases, persistent, foul-smelling, or bloody discharge warrants veterinary assessment. Discharge accompanied by swelling, heat, lameness, or systemic signs such as fever or elevated heart rate requires prompt attention. See also pasture safety for wound risks that can produce discharge-causing injuries.

Further Reading

Medical discharge as a clinical sign is described in the medical discharge article on Wikipedia. Systemic conditions in horses that present with abnormal discharge are addressed in the Merck Veterinary Manual section on Disorders Affecting Multiple Body Systems of Horses.

A dewlap is the loose, pendulous fold of skin that hangs from an animal’s throat or the underside of the neck. The term refers to the anatomical structure itself, the excess skin and associated connective tissue, rather than to a pathological condition. In horses, a true dewlap is not a typical feature of normal conformation; the term is more commonly applied to cattle, dogs, and reptiles, where the structure is a consistent anatomical feature of certain breeds or species.

In horses, loose skin or folds beneath the throatlatch region can appear in very old animals, in those that have lost significant weight, or in some heavy draft breeds with naturally coarser skin. These are not dewlaps in the anatomical sense but are sometimes described informally using the term. A genuine dewlap involves redundant skin as a breed-standard feature, as seen in Zebu cattle and several dog breeds where the structure is genetically fixed.

Understanding the term is relevant when reading veterinary or comparative anatomy references that describe cervical (neck) structures across species. When the term appears in equine health contexts, it typically describes a infected skin-fold discharge-producing or inflamed skin fold rather than a true anatomical dewlap. Any persistent fold of the underlying dermal layer tissue that shows signs of irritation, discharge, or thickening in the neck or throatlatch region warrants veterinary assessment, as skin folds trap moisture and can become sites of infection.

Further Reading

The dewlap as an anatomical feature across species is described in the dewlap article on Wikipedia. Physical examination and anatomy in routine equine care are covered in the Merck Veterinary Manual section on Routine Care and Breeding of Horses.

Disposition is a horse’s characteristic attitude or temperament, its consistent, habitual way of responding to people, handling, stimuli, and work. A horse’s disposition is distinct from its mood on a given day; it describes a stable pattern of behavior that emerges across different situations and over time. The term is used interchangeably with temperament in equine contexts, though temperament more often emphasizes the innate, heritable component, while disposition includes the influence of handling and experience.

Common descriptors include willing, honest, bold, sensitive, difficult, nervous, quiet, and hot. A willing or easy disposition means the horse generally cooperates with requests, tolerates new experiences without excessive alarm, and recovers quickly from stress. A hot or difficult disposition describes a horse that reacts strongly, is easily startled, or resists handling, which may be a breed characteristic, a response to pain or poor training history, or an individual trait. stallion temperament tendencies often require more careful handling than gelding as a management choice because the hormonal profile influences disposition toward assertiveness and distraction.

Breed tendencies in disposition are well documented: American Saddlebreds are described as sensitive and animated; draft breeds tend toward a calmer, more phlegmatic disposition; hot-blooded breeds including the Arabian are typically alert and reactive. These are population tendencies, not individual guarantees. When evaluating a horse for purchase, disposition assessment, watching how the horse responds to grooming, tacking up, leading, and unexpected stimuli across multiple visits, is as important as body condition and soundness. A first-time owner benefits most from a horse with a forgiving, calm disposition that tolerates mistakes without escalating.

Further Reading

The science of animal temperament is introduced in the temperament article on Wikipedia. How disposition influences equine handling, training, and welfare is covered in the Merck Veterinary Manual section on Behavior of Horses.

Dehydration is the medical condition in which a horse’s body has lost more fluid than it has taken in, creating a net deficit of water and electrolytes. The condition exists on a continuum: mild dehydration (three to five percent bodyweight loss in fluid) causes reduced performance and dry mucous membranes, while severe dehydration (above eight percent) carries risk of circulatory collapse, kidney failure, and death if untreated.

The skin pinch test is a primary field indicator: tenting of the skin for more than two seconds after release indicates significant dehydration. Gum assessment provides a second data point, normal gums are pink and moist with a capillary refill time under two seconds; dehydrated horses show tacky, pale, or gray gums and prolonged refill. In severe cases, sunken eyes, an elevated heart rate, and signs of impaction and colic risk accompany fluid deficit. Treatment requires oral or intravenous fluid replacement, with electrolyte supplementation when losses are primarily from sweating.

Prevention centers on consistent water access. An adult horse requires twenty to forty liters of water per day at rest, with requirements rising sharply during exercise and hot weather. Winter dehydration is underrecognized; horses often refuse cold water and reduce intake, increasing impaction colic risk. Feed management plays a role: high forage diets increase water consumption naturally. See also clinical causes and treatment for a full clinical guide covering causes, assessment protocol, and recovery.

Further Reading

Background on the physiology of dehydration is available in the Wikipedia article on dehydration. Clinical management of fluid deficits in horses is addressed in the Metabolic Disorders of Horses chapter of the Merck Veterinary Manual.

To dehydrate means to lose water or moisture from a living body in excess of what is being replaced, creating a net fluid deficit. In horses, dehydration occurs when fluid losses, through sweating during exercise, elevated respiratory rate, illness, or environmental heat, exceed water intake. A horse that is dehydrating shows a progressive series of signs ranging from mild performance decline to life-threatening organ dysfunction.

The skin pinch test is a standard field assessment: pinching a fold of skin on the neck and releasing it should result in the skin snapping back within one to two seconds; a delayed return indicates the horse is dehydrating and requires intervention. The gum color and capillary refill time are also evaluated, pale, dry, or tacky gums with a refill time over two seconds are consistent with significant fluid loss. A horse begins to dehydrate measurably at roughly three to five percent bodyweight loss in fluid.

Horses dehydrate more rapidly in hot, humid weather or during heavy exercise, because sweat is the primary cooling mechanism and horses produce large volumes of it under exertion. The risk compounds in winter, when horses often reduce water intake when water temperature drops. A horse that is dehydrating and not treated can develop colic from poor gut motility, reduced gut motility, and impaired kidney function. See full clinical guide for clinical detail on causes, stages, and treatment.

Further Reading

The physiology of fluid loss is described in the dehydration article on Wikipedia. For veterinary guidance on fluid and electrolyte disorders in horses, see Metabolic Disorders of Horses in the Merck Veterinary Manual.

Docile describes a horse that is gentle, willing, and easy to handle. The term refers to a temperament marked by calm responses to human contact, grooming, tacking, and work under saddle or in harness, not merely passivity, but active cooperation without fear or resistance. A docile horse does not bolt from routine stimuli, accepts new environments without prolonged agitation, and allows handlers to move around it safely.

Temperament in horses has both a heritable component and an experiential one. Selective breeding programs, particularly those producing American Saddlebreds and other show breeds, have historically favored docility as a trainability trait. Hot-blooded breeds bred for speed and reactivity are not typically selected for docility, though individual animals within any breed vary considerably.

Docility matters most in contexts where the horse works closely with inexperienced or physically limited handlers: therapeutic riding programs, lesson programs, trail operations, and children’s mounts. The body condition and temperament and management routine of a horse also influence expressed temperament; a horse in pain, malnourished, or rarely handled may behave less docilely than its baseline disposition would suggest.

Veterinary and behavioral assessments distinguish docility from learned helplessness. A truly docile horse remains attentive and engaged; a horse made compliant through suppression or fear may appear docile but remains a safety risk. Evaluating a horse’s temperament before purchase is addressed in the evaluating temperament before purchase and the list of questions to ask before boarding.

Further Reading

The concept of docility as a behavioral trait is introduced in the docile entry on Wikipedia. How temperament and behavior affect horse handling and welfare is covered in the Merck Veterinary Manual section on Behavior of Horses.

Dermal means relating to or of the dermis, the layer of skin beneath the epidermis (outer surface layer). In general equine anatomy, the term describes any tissue, structure, or condition associated with the skin or dermis. The skin is the horse’s largest organ, functioning as a barrier against infection, a thermoregulatory surface, and a sensory interface with the environment.

In hoof anatomy, the dermal laminae (also called sensitive laminae) are the blood-rich tissue structures inside the hoof wall that interlock with the epidermal laminae of the hoof capsule, binding the internal hoof structures to the hoof wall. When this connection is disrupted, as in laminitis, the dermal laminae become inflamed and the bond between hoof wall and coffin bone fails. The dermal distinction matters clinically: procedures and injuries that penetrate to the dermal layer of the hoof involve live, sensitive tissue and carry a risk of bleeding and infection absent from purely superficial (epidermal) damage.

Dermal issues in the broader skin include conditions such as rain rot (dermatophilosis), dermal cysts, and allergic reactions that affect the dermis. A wound discharge at the dermis from a dermal lesion or wound indicates that the dermis is breached. Veterinarians use the term to distinguish surface from depth in wound assessment, a dermal wound has penetrated the epidermis, while a wound described as reaching the subcutaneous or dermal layer requires more care than a superficial abrasion. See the surface anatomy reference for a structural reference to where dermal surfaces are examined.

Further Reading

The structure and function of skin are described in the skin article on Wikipedia. Conditions affecting the dermal layer in horses, including dermatitis and rain rot, are covered in the Merck Veterinary Manual section on Skin Disorders of Horses.

Buck is the movement in which a horse drops its head toward the ground, rounds and arches its back, and kicks out with both hindlegs simultaneously or in rapid succession, projecting the hindquarters upward. The action is a natural equine behavior, horses in open pasture buck during play, at the start of a fast canter, or when energized by cold weather. Under a rider it is dangerous: a bucking horse can unseat its rider and, if the bucking is severe, cause a fall.

Bucking during ridden work carries clinical significance. A horse that bucks consistently at the canter transition, when leg is applied, or on a particular rein is often communicating pain rather than resistance. Back pain, ill-fitting saddle, hock soreness, and gastric ulcers are common physical causes. A horse that has bucked successfully in response to an uncomfortable stimulus has been reinforced to repeat the behavior, which is why distinguishing pain-driven bucking from learned behavior requires a veterinary workup before a training intervention.

In rodeo sport, bucking is a formalized and scored discipline. Rodeo broncs, both saddle bronc and bareback, are selected and bred for their athletic bucking ability, and the sport scores both the animal’s performance and the rider’s. In cutting and reining, a horse that bucks unexpectedly is disqualified. The term also appears in the phrase “bucking out”, a horse blowing off excess energy with a short burst of bucks before settling into work, which is distinct from sustained or violent bucking. Understanding what precedes a buck is the diagnostic starting point for addressing it.

Further Reading: The Wikipedia article on bucking in horses covers the behavior’s natural context and rodeo applications; the Merck Veterinary Manual’s section on lameness in horses is the clinical starting point for diagnosing pain-driven bucking.

Defecation is the expulsion of fecal matter from the body through the rectum and anus, completing the process of digestion. In horses, the frequency, consistency, and appearance of fecal output are primary indicators of digestive health. A healthy adult horse typically defecates eight to twelve times per day, producing well-formed fecal balls that are moist but hold their shape.

Changes in defecation pattern are among the earliest clinical signs of digestive problems. Absence or significant reduction of defecation, particularly when accompanied by pawing, rolling, or elevated heart rate, is a classic warning sign of impaction colic risk. Conversely, loose, watery, or unusually frequent fecal output, loose stools as a deviation: signals a separate category of gastrointestinal disturbance. Both deviations warrant prompt veterinary attention.

In practice, monitoring defecation is standard in daily horse care: stall managers check manure volume and consistency at every cleaning, and an absence of fecal output in a stall overnight is an immediate concern. During fecal testing for parasite management, a fresh fecal sample is collected from defecation and analyzed for egg counts to guide deworming decisions. Defecation is also considered alongside hydration status when assessing overall gut motility.

Further Reading

For the biology of defecation, see defecation on Wikipedia. Equine digestive conditions related to fecal output are covered in the Digestive Disorders of Horses section of the Merck Veterinary Manual.