Module Paard: Equine Anatomy, Behavior, Reproduction, Diseases, Toxicology, and Parasitology

Comprehensive vocabulary flashcards covering equine anatomy, behavior, reproduction, medicine, toxicology, and parasitology.

Equine Directional Terminology

Anatomical reference terms: Cranial (towards the head) vs. Caudal (towards the tail); Dorsal (towards the back/topline) vs. Ventral (towards the belly); Proximal (closer to the trunk) vs. Distal (further from the trunk); Rostral (towards the nose/muzzle, used on the head); Lateral (away from the midline) vs. Medial (towards the midline); Palmar (back of the forelimb below the carpus) vs. Plantar (back of the hindlimb below the tarsus).

Distal Limb Flexor Apparatus

The supportive soft tissue structures running along the palmar/plantar aspect of the cannon bone: Oppervlakkige buigpees (superficial digital flexor tendon), Diepe buigpees (deep digital flexor tendon), Check ligament (accessory ligament of the deep digital flexor tendon), and Tussenpees / Interosseus (suspensory ligament).

Wolf Tooth (Wolfstand)

A small, vestigial premolar tooth (eruption of a rudimentary tooth germ) located immediately in front of the first functional cheek tooth; it is commonly extracted by an equine dentist because it can cause interference and discomfort when the horse is ridden with a bit.

Equine Incisor Eruption Schedule

The permanent incisors erupt from inside to outside at predictable ages: central incisors at $2.5\text{ years}$, middle incisors at $3.5\text{ years}$, and outer (corner) incisors at $4.5\text{ years}$, with full permanent dentition achieved by $5\text{ years}$ of age (totaling between $36$ and $44\text{ teeth}$).

Mare Estrous Cycle Hormones

The hormonal regulation of the mare's $\sim 21\text{-day}$ reproductive cycle, characterized by rising Estrogen peaking before ovulation, an LH surge triggering ovulation, Progesterone secreted and maintained by the corpus luteum (CL) during diestrus, and a spike of PGF2$\alpha$ around day $14 - 16$ causing luteolysis if the mare is not pregnant.

Blitzen (Winking of the Vulva)

A characteristic behavioral sign of estrus (hengstigheid) in mares involving rhythmic eversion of the clitoris and labia of the vulva, typically accompanied by frequent urination of cloudy urine, tail deflection, and a standing stance.

Teasing (Schouwen)

The daily management practice of bringing an intact stallion near a mare across a safe barrier to evaluate her behavioral receptivity and determine the optimal timing for mating or insemination without risking physical injury.

Artificial Insemination (KI) Viability Windows

Fresh stallion semen remains viable for $36 - 48\text{ hours}$, whereas frozen semen remains viable for only $12 - 20\text{ hours}$; because the unfertilized ovum has a lifespan of $6 - 24\text{ hours}$, insemination is ideally performed within $8\text{ hours}$ following ovulation.

Embryo Transfer (ET) in Horses

A reproductive procedure in which a fertilized embryo is flushed from a genetic donor mare (usually around day $7 - 8$) and transferred into the synchronized uterus of a recipient surrogate mare, yielding a successful live foal in approximately $1\text{ out of 4}$ flush procedures.

Twin Pregnancy Management (Tweelingdracht)

Detection of twin embryonic vesicles via ultrasound between day $14$ and $18$ ($\sim 19\text{ mm}$ vesicle), requiring the manual crushing (pinching) of one vesicle before day $16$; if twins persist past day $34$, the pregnancy is medically terminated via hormone injection to abort both embryos due to severe risks.

Breech Presentation (Stuitligging)

An abnormal presentation where the fetus enters the birth canal rear-feet first with the hind legs extended towards the vulva; unlike other dystocias, foals in this specific orientation can often be delivered without veterinary surgical intervention.

Bilateral Hip Flexion (Beiderzijdse Heupligging)

A severe form of dystocia where the fetus is in a posterior presentation with both hind legs folded forward underneath its body, presenting only the tail at the pelvic entrance; requires immediate veterinary intervention to extend the limbs, and may necessitate a Cesarean section.

Retained Placenta (Aan de nageboorte staan)

Failure of the mare to expel fetal membranes within $3\text{ hours}$ post-partum (normal expulsion occurs within approximately $45\text{ minutes}$ to $2\text{ hours}$); considered a veterinary emergency due to high risk of toxic metritis, endotoxemia, and secondary laminitis.

Neonatal Foal Milestones

Standard postpartum timeline: righting and suckling reflexes appear immediately; standing unassisted within $1 - 2\text{ hours}$; nursing colostrum within $2\text{ hours}$; first urination within $4 - 6\text{ hours}$; and passage of first meconium within $12 - 24\text{ hours}$ (ideally starting by $3\text{ hours}$).

Bachelor Band

A social herd composition consisting of young stallions that form alliances, establish bonds, and practice fighting and social skills until reaching social maturity ($6 - 9\text{ years}$ of age) to challenge herd stallions and obtain their own harem.

Wild Equine Daily Time Budget

The natural allocation of time in free-roaming horses: Eating ($64\%$), Resting ($23\%$), Standing ($6\%$), Locomotion/Moving ($3\%$), Social interaction ($2\%$), and Other activities ($2\%$).

Stereotypic Stable Vices (Stalgebreken)

Compulsive, abnormal repetitive behaviors developed due to chronic confinement, lack of foraging, and social deprivation, including box walking (cauterizing joint/tendon overload), weaving (lateral weight-shifting damaging the musculoskeletal system), and crib-biting/windsucking (causing tooth wear and gastric ulcers).

The Equine Pain Face

A validated diagnostic facial grimace scale indicating pain, characterized by lowered ears with increased inter-ear distance, contraction of the m. levator anguli oculi medialis causing an angled skin tension above the eye, a tense stare, mediolaterally dilated nostrils, and an angular, tight muzzle with flattened chin.

Equine Resting Vital Parameters (Normaalwaarden)

Standard physiological baseline parameters for a healthy adult horse at rest: Respiration rate of $8 - 14\text{ breaths/min}$, Pulse/Heart rate of $28 - 40\text{ beats/min}$, and Rectal body temperature of $37.4 - 38.0\,^\circ\text{C}$.

Strangles (Droes)

A highly contagious upper respiratory bacterial infection caused by Streptococcus equi subspecies equi, causing high fever, mucopurulent nasal discharge, and severe submandibular and retropharyngeal lymph node abscessation; may develop into metastatic 'bastard strangles' (verslagen droes) if abscesses spread systemically to internal organs.

Equine Herpesvirus Myeloencephalopathy (EHM)

The neurological disease form of Equine Herpesvirus-1 (EHV-1), clinically manifesting as ataxia (incoordination), hindlimb paresis or paralysis, urinary incontinence/bladder paralysis, and a flaccid tail, carrying a fair-to-good prognosis only if the recumbent horse does not remain down for longer than $24\text{ hours}$.

Pituitary Pars Intermedia Dysfunction (PPID)

A neurodegenerative hormonal disorder caused by loss of dopaminergic neurons in the hypothalamus, leading to intermediate lobe pituitary hyperplasia and excessive hormone production; classic symptoms include hirsutism (hypertrichosis/long curly coat), muscle wasting, supraorbital fat pads, polyuria/polydipsia, and recurrent laminitis.

Exertional Rhabdomyolysis (Maandagziekte / Spierbevangenheid)

An acute metabolic breakdown of skeletal muscle fibers triggered by an imbalance between high-concentrate feed intake and inadequate exercise during rest days; marked by hindquarter stiffness, sweating, severe pain, elevated muscle enzymes (CK and AST), and myoglobinuria (coffee-brown urine).

Equine Laminitis Pathophysiology

A crippling inflammation and structural failure of the interdigitating epidermal and dermal lamellae suspending the coffin bone (hoefbeen) within the hoof wall; the tensile pull of the deep digital flexor tendon (buigpees) overcomes the compromised lamellae, causing downward rotation and sinking of the pedal bone toward the sole.

Sweet Itch (Zomereczeem)

A common seasonal type I and IV hypersensitivity reaction to the saliva of biting midges (Culicoides robertii / Culicoides spp.), active from March to late October, leading to severe pruritus, mane and tail rubbing, hair loss, skin thickening, and secondary excoriations.

Cellulitis / Lymphangitis (Einschuss)

An acute bacterial infection of the subcutaneous tissues and lymphatic vessels (most frequently caused by Staphylococcus or Streptococcus via minor skin wounds or mud fever/mok), presenting as massive warm, painful limb edema, fever, and severe lameness; untreated cases can progress into irreversible chronic elephantiasis (olifantsbeen).

Buxus Poisoning (Buxine)

Severe intoxication caused by the alkaloid buxine found in the leaves, bark, and seeds of boxwood; ingesting as little as $750\text{ g}$ causes central nervous system depression, violent gastrointestinal cramps, and death from respiratory paralysis within $30\text{ minutes}$.

Taxus Poisoning (Taxine)

Lethal cardiotoxic poisoning caused by taxine alkaloids present in all parts of the yew tree (Taxus baccata); ingestion of a single sprig can cause transient excitation followed by sudden collapse, cardiac arrest, and death due to anoxia within $15\text{ minutes}$.

Atypical Myopathy (Atypische Myopathie)

An acute, fatal non-exertional rhabdomyolysis caused by the toxin Hypoglycin A present in the seeds, leaves, and seedlings of the sycamore maple (Gewone esdoorn / Acer pseudoplatanus); severely impairs skeletal and respiratory muscle lipid metabolism, resulting in recumbency, dark urine, and a $70\%$ mortality rate.

Ragwort Toxicity (Jacobskruiskruid)

Poisoning caused by pyrrolizidine alkaloids in Senecio jacobaea, which retain toxicity when dried in hay; chronic ingestion causes cumulative, irreversible liver cirrhosis, manifested by weight loss, icterus, photosensitization, and terminal hepatic encephalopathy (razende kolder).

Alsike Clover Poisoning (Bastaardklaver)

Intoxication occurring on acidic, wet pastures or through hay contaminated with Trifolium hybridum; high intakes lead to acute hepatic necrosis, secondary photosensitization of non-pigmented skin, jaundice, compulsive circling, and head-pressing.

Equine Botulism

A severe neuroparalytic disease caused by the neurotoxin of Clostridium botulinum (contracted from decaying carcasses in big-bale silage, rotting aquatic matter, or wound infection), which blocks acetylcholine release at the neuromuscular junction, producing flaccid paralysis, dysphagia, tremors, and recumbency.

Amitraz Toxicity in Horses

Poisoning caused by accidental exposure to the antiparasitic drug Amitraz (used on cattle/dogs), which excessively stimulates alpha-2 adrenergic receptors and the sympathetic nervous system, inducing marked intestinal hypomotility, lethal impaction colic, and functional ileus; treated with the antagonist atipamezole.

Lolitrem B Mycotoxicosis

A neurotoxic mycotoxin produced by the endophyte Neotyphodium lolii found in perennial ryegrass; exceptionally heat- and drought-stable (persisting in hay), causing ryegrass staggers, muscle tremors, hyperexcitability, ataxia, and muscle spasms $5 - 10\text{ days}$ after ingestion.

Slaframine (Slobber Compound)

A mycotoxin produced by the fungus Rhizoctonia leguminicola (black patch) on forage and legumes; induces a potent histaminergic/parasympathomimetic reaction within $30 - 60\text{ minutes}$, marked by profuse hypersalivation (speekselvloed), polyuria, lacrimation, and occasional diarrhea.

Equine Endoparasite Life Cycle

The fecal-oral transmission cycle of common equine intestinal nematodes: adult worms shed microscopic eggs in manure onto pastures; eggs embryonate and hatch into infective third-stage larvae ($L_3$) on grass blades; grazing horses ingest larvae, which migrate and mature internally, causing colic, unthriftiness, and diarrhea.

Targeted Selective Deworming (Mestonderzoek)

Modern parasite control strategy relying on quantitative fecal egg counts (FEC) $2 - 3\text{ times}$ per year (March, June, September) for adult horses ($> 3\text{ years}$), treating only the $\sim 20\%$ of horses that shed significant egg quantities to prevent anthelmintic resistance, alongside one routine late-autumn treatment against tapeworms.

Equine Influenza Primary Vaccination Protocol

A three-dose basic immunization regimen starting at $6\text{ months}$ of age: 1st primary injection, 2nd injection $4 - 6\text{ weeks}$ later, and 3rd booster injection $5\text{ months}$ after the second ($6\text{ months}$ after the first), followed by mandatory annual or bi-annual boosters.

Maternal Immunity in Foals (Biest)

The passive transfer of maternal immunoglobulins to the neonate strictly via colostrum within the first $12 - 24\text{ hours}$ of life (epitheliochorial placenta prevents in utero transfer); foal's endogenous immune system only becomes fully functional around $6\text{ months}$ of age.