Horses

HorsesEquine

Mule- hybrid, cross between horse and donkey

- Infertile

Horse terminology

• Horse- generic term for any equine, intact male 5 yrs of age or older

• Colt- intact male 4 yrs old or less• Gelding- castrated male at any age• Rig/ridgling- male with one or both testicles

absent from scrotum• Mare- female 5 yrs of age or older• Filly- female 4 yrs of age or younger

• Foal- either sex from birth to weaning ( 4-6 mo)

• Weanling- either sex from weaning to 12 months of age

• Yearling- either sex 12-23 mo• Maiden- a horse of either sex that has not

won a competition, female that has not had a foal

• Hand- horses height is measured in hands at the highest fixed point, the withers, one hand is 4 inches

• Near side- left side of horse• Far/off side- horses right side• Cold blooded/hot blooded- refers to

temperament of the horse• Stallion- intact male

Colors of Horses

• Bay- Brown haircoat- Black mane and tail- Black points, muzzle, distal limbs- +/- dorsal stripe

• Chestnut/sorrel- red, copper colored coat- Same colored mane, tail or flax colored mane

and tail• Grey- dapple, flea bitten- All grey horses are born dark, black, lighten

with age

• Black- Very rare color, no brown hair on muzzle,

flanks, medial limbs• Dun, buckskin- Tan to honey color, black mane and tail- Black points, dorsal stripe- +/- horizontal stripes on limbs

• Palomino- Cream to dark honey colored haircoat- White mane and tail- No black markings• Roan- White hairs interspersed in coat, color does not

change significantly with age- Red roan- chestnut base coat- Blue roan- black or grey base coat

Head Markings

• Star• Strip• Snip• Blaze• Bald face

Leg markings

• Coronet• Half pastern• Pastern• Sock• stocking

Identification

• Tatoo• Freeze brand- applied with liquid nitrogen,

hair grows in white• Heat brand- heated iron, hair does not grow

back• Microchip- in middle 1/3 of neck in nuchal

ligament• Foal certificates- detailed physical description

Common Breeds

• Quarter horse• Paint horse• Arabian• Thoroughbred• Appaloosa• Morgan• Tennessee walker• Standardbred• Draft horse

Draft horse breeds

• Clydesdale- feathers, blaze, mostly bay, Budweiser horses• Belgian- Chestnut to palomino, blaze• Percheron- black, dappledPoniesShetland, Hackney

Psychology of prey animals

• Safety- If a horse does not feel safe, its handler is not

safe- Training, interaction with a horse cannot

progress if horse feels unsafe, if frightened- Physical punishment, installation of fear is not

an appropriate training technique

• Food:- Bribing a horse with food is no more effective

than buying a misbehaving child food to get him to settle down

- Food may be used as a reward for correct behavior but care must be taken

• Comfort:- Training zone- Given a choice, horse will choose comfort- Horses do not seek approval the way dogs do,

if they do something right its because they see a benefit for themselves in the behavior

• Defenses:- flight, evasion- Biting- Kicking- striking

Physiology of Prey animals

• Gastrointestinal- continuous gastric acid secretion, permits constant, continuous ingestion of small amounts of feed, grazing

• Musculoskeletal- Stay apparatus- permits horse to sleep standing

up, horse appears larger to predators and its ability to flee is enhanced

- Nuchal ligament- allows horse to hold head up without muscular effort, energy

• Reproductive- Stage II labor is less than one hour- Foaling occurs 12-3 am- Foal is ambulatory, able to keep up with herd

within 6 hours of birth

Sensory Capabilities of the horse

• Vision1. monocular, single eye field of vision- Depth perception is based on memory- Unable to triangulate to identify size or

distance of unfamiliar items2. binocular, two eye field of vision- ears, eyes rotate forward- 65 degrees

3. Color perception- Dichromatic- Red, blue and gray4. Night vision- Rods predominate in retina- Acute, better than humans and most

predators night vision

5. Hearing- Ears swivel independently- Can precisely locate origin of sound,

triangulation- Can listen in several directions at once- Ear position indicates what horse is listening

to

6. Olfactory- Recognition of other herd members, humans- Recognition of reproductive status of horses in

the herd7. Tactile- Grooming behavior establishes social bonds and hierarchy within the herd

Interaction with the horse

1. Equine body languagea. Warning signals/threatening behavior- Pinning ears, baring teeth- Turning hindquarters toward intruder, lifting

hind legb. compliant/non threatening behavior- Ears forward, head in neutral position, chewing

• Human body language- Eye contact with the horse acknowledges horses

presence- Maintaining eye contact is a sign of dominance, be

careful who you challenge- Physical approach, approach diagonally, to the

shoulder, least threatening, - Physical contact, contact trunk before limbs- Let hand tell horse where you are going- Push, don’t pull

General Terms

• Tack- equipment• Cinch girth- holds saddle on, some horses able

to puff chest out so girth can get loose• Bit- part in mouth• Shod- put shoes on, having shoes on• Sulky- special racing cart• Hunter- jumps fences• Float- filing teeth

• Cribbing and windsucking- take top teeth and put them on a hard surface, uses neck muscles just right to suck in air.

• Weaving- going back and forth in place• Furlong- distance measured on a racetrack• Cover- stallion breeds the mare• Whirl- cowlick on head

Restraint Basics

• Safety- the individual restraining the horse is responsible for the safety of all persons present

• Halter- allows you to control the horses head, if you can control the head, you can control the horse

Lead Shank

• Never tie yourself to a horse• Never leave a lead shank on the ground• Applicationsa. Chain over noseb. Chain over gums, not appropriate for leading

a horse

Tying

• Always use a quick release knot• Always tie at or above head level• Use tie length that will not permit horse to get

a leg over slack and get entangled

Twitch

• Induces release of endorphins, duration of effect 15 minutes• Not appropriate for procedures of longer duration• Long handled twitchSkin Twitch• Grabbing hold of skin over shoulder, diverts horses attention• Redirects horses apprehension, anticipation, does not induce

endorphins, just distractionEar Hold• Useful for steadying the head

• Center of gravity- Make it physically difficult for horse to kick, rear

or evade- In order for a horse to rear, he must shift all his

weight onto his hind legs- Prevent weight, prevent rearing- Horse at rest carries 60% of his weight on front

legs, increasing speed increases the %- To keep him from rearing, keep him moving

Stocks

• Most commonly used for reproductive procedures

• Rectal palpation, ultrasound, AI, embryo transfer

• Still requires a handle at the head• Always be aware of your position with respect

to rigid immoveable structures

• Breeding hobbles- prevent mare from kicking stallion during breeding

• Tail tie- useful in anesthetic recovery and management of neurologic patients

• Sling- useful in neurologic patients, rescue situations, management of starvation cases

- Introducing horse to sling must be done carefully as flight response is very strong

Equine Dentistry

• Age determination- Educated guess regarding age of horse- Wear patterns affected by diet, behavior,

anatomic abnormalities, trauma- Teeth do not grow, they continually erupt over

horses lifetime- Healthy horses die of old age because of tooth

loss, inability to access nutrients- NOTE: upper molars extend into frontal sinus

• Deciduous incisors eruptI1- 6 daysI2- 6 weeksI3- 6 months• Adult incisors erupt at, and wear at- I1- 2 ½ years 3 years- I2- 3 ½ years 4 years- I3 – 4 ½ years 5 years

Cups Disappear

• Upper I1 6 years• Upper I2 7 years• Upper I3 8 years• Lower I1 9 years• Lower I2 10 years• Lower I3 11 years

Occlusal surface of incisors changes from retangular to triangular as horses age

• Galvaynes groove (I3)- Appears 10 years- Extends ½ down tooth 12 ½ years- Extends entire tooth 15 years- ½ way gone 17 ½ years- Gone 20 years

Incisor Angle

• Becomes more acute as a horse ages• Caps- decidous teeth that remain present on

the erupting surface of adult teeth• Canine teeth- found almost exclusively in

males• Wolf teeth- first premolars, normally extracted

when a young horse is trained to accept bridle

• Bars- toothless region on mandible between incisors and molars. The bit sits here. Site where oral meds are given

• Eruption bumps- rounded boney enlargements palpated on bottom of lower jaw when adult molars are erupting. Normal in 2-4 yr olds. Not painful

• Parrot mouth- overbite, impairs horses ability to tear off grass or bite pieces of hay.

Locomotion/lameness

• Locomotion- bipedal- 2 legged, center of gravity thrown

forward, limb extended to break the fall- Quadripedal- 4 legged, wheelbarrow effect

( 60%, 40% weight distribution)

Gaits

• Walk- 4 beat gait- No suspension phase- LH, LF, RH, RF• Trot/jog- symmetrical, 2 beat gait- 2 legs bearing weight at once- Suspension phase ( all 4 legs off ground)- LH/RF RH/RF ( legs on one side move in unison)

• Pace ( standardbred only)- LH/LF RH/RF ( legs on same side move in unison)• Canter/lope- Asymmetrical 3 beat gait, 1 foot down, 3 feet follow- Lead foreleg, single leg loaded with entire body

weight- When circling, the horse should be on the inside

lead- LH- RH LF RF

• Tennesse Walkers is a manufactured gait

Hoof Care

• No foot, no horse• 90% of lameness is in the foot• Hoof management- sanitation, moisture control- Hygiene: hoof pick, hoof maintenance,

shoeing, trimming interval- Footing: weight must be born on hoof walls,

not sole, deep sand can bruise foot

Horseshoeing

• Protection• Traction• Support• Therapeutic/orthopedic correction- Angle- Toe length- Increased support- Weight adjustment

Lameness evaluation

• Passive evaluation- pointing a limb, reluctance to move

• Gait analysis- best performed at a trot, straight line and circling in both directions

- Head nod: horse alters center of gravity to decrease weight load on painful leg

- Sound of horses hooves striking hard pavement at trot may indicate uneven weight load even without head nod

• Palpation: cardinal signs of inflammation- Rubor- redness- Dolor- pain- Tumor-swelling- Calor- heat• Diagnostic nerve blocks- gait eval after block• Radiology- bone evaluation

• Ultrasonography- soft tissue evaluation• Nuclear scan- injection of radioactive material

and detection of distribution in tissues- Note: feces, urine, bedding radioactive for 24

hours, special disposal license- Hot imaging: radioactive nucleotide

accumulates in areas of bone remodeling- Cold imaging- absence of radioactive material,

ex cold spot in lung due to abcess

Common Lamenesses

• Buck shins- tearing or damage to soft tissue in front of cannon bone

• Splints- lateral and medial to cannon bone- Additional bone growth on splint bone and

soft tissue between splint bone and cannon bone caused by trauma

• Suspensory ligament injury- Supports fetlock, ( ankle)- Harder to heal- Rest is key• Bowed tendons- Can happen with overexertion- Similar to sprained wrist in humans- Ruptured tendon is very bad- Cold therapy and supportive wraps, blistered, fired,

laser, ultrasound and magnets

• Osselets- Injuries to front of fetlock joint- Bulging and round- Excessive trauma and tearing of soft tissue• Ringbone- Boney growth in pastern area in the joints- Foot swollen around coronary band- Low ringbone is just below fetlock- High ringbone sometimes resembles splint

• Sidebone- Involves coffin bone- Calcifies due to traumatic injury• Grease heel- Irritation of skin caused by dirt, wet

environment- Infection of sebaceous gland

• Gravel hoof- Irritation to sole of hoof on white line- Irritation or separation causes infection which

comes out at coronary band• Sole abcess- Trauma to sole and infection• Thrush-bacteria that live in horses hoof, similar to foot rot- Chlorox and water to clean feet and stalls

• White line disease- Bacteria in white line of horses hoof- Sloughs hoof wall and shoe• Navicular disease- Navicular bone behind coffin in hoof- Horse acts like he is walking on glass- Correct diet, correct shoeing

• Laminitis- Founder- Inflammation of sensitive lamellae of hoof- Coffin bone rotates downwards- Mild to extensive- Shoeing to help correct

Treatment terms

• Freeze- liquid nitrogen• Fire- electrical iron, pin fire to cause irritation

and healing• Neurectomy- denerving foot to make horse

“sound”, very dangerous• Corrective shoeing- changing angles of feet

and legs

Treatments

• Adequan- Inhibit lysosomal enzymes- Reduce synthesis of prostaglandins- Stimulate production of hyaluronic acid- Create chondroprotection

• Legent ( sodium hyaluronate) - Increases lubrication- Decreases prostaglandins- Stimulates production of hyaluronic acid- Systemic or in joint

• Corticosteroids- Relief from pain and inflammation- Stabilizes lysosome membrane- Decreases vasodilation to decrease edema

and fibrin deposition- Decreases neutrophils- Decrease prostaglandins

Equine Colic

• A symptom, not a diagnosis• Abdominal pain• Causes- Gastrointestinal- Uterine contractions, abortion, foaling, uterine

involution post foaling- Urethral, cystic calculi, peritonitis- Administration of PGF2alpha- Referred thoracic pain, myocardial infarction, pleuritis- Testicular torsion

• Clinical signs- sweating, pawing- Looking at flanks- Frequent lying down then getting back up,

sometimes violently- Rolling, stretching out as if to urinate- Straining to urinate or defecate

GI tract of horse

• Protection- Physical barrier to keep outside in and inside

out, immune function• Elimination- waste, non-digestible materials, bile, bacteria,

parasites, water• Absorption of nutrients, water• Secretion of digestive enzymes, water

24 hours maintenance intake

• Horse consumes2-3% of body weight in roughage ( 20-30 lb/1000lb bw)

• Horse consumes 10-15 gallons of water a day

GI diseases that can result in colic

• Inflammation- Gastric ulcerationa. foals- secondary to stress, concurrent diseaseb. Adults- management related- enteritis: viral- Potomac horse fever- bacterial- Typhlitis, inflammation of cecum, parasitic

(tapeworms)

• Displacement without displacement ( gas colic)

- Often weather related- Decreased barometric pressure> increased gas

volume ( boyle’s law)

• Obstruction- ingesta-impaction-associated with decreased

water intake- Parasites, ascarids- Meconium- foals swallow amniotic fluid with

meconium- Enteroliths in older horses, often form around

a foreign body

• Displacement without strangulation- Pelvic flexure displacement- Right dorsal displacement- Left dorsal displacement

• Displacement with strangulation- hernia: umbilical, inguinal, scrotal- Epiploic foramen entrapment, mesenteric tear- Strangulation lipomas- Intussesception- altered segmental peristalsis

often secondary to diarrhea or parasitism- Volvulus, torsion

• Ishemia/ischemic necrosis ( without displacement) thromboembolic colic

• Rupture- Gastric perforation due to ulceration or bots- Intestinal colonic rupture secondary to

ischemia

Diagnosis of colic

• Diet- type, amount, quality of feed, frequency of

feeding- Change in diet????• Exercise- Type- Frequency, intensity, pattern of exercise- Changes in exercise

• Deworming- frequency, product used- Reliability of administration- Fecal exams to detect small resistant

strongyles

• Management- Housing in groups or individually, competition

for feed can lead to bolting food- Pasture vs stall- Sand lot- Water supply, quality

• Reproductive status• History of previous colic episodes• Behavioral abnormalities such as cribbing,

eating habits• Level of management, monitoring

Physical exam for colic

• Temperature- >105 inflammatory disease ex. Enteritis - 99-100.8 normal, does not rule out serious

disease- <99 hypovolemic shock, devitalized tissue

• Pulse- <44 normal does not rule out serious disease- 48-66 pain, +/- cardiovascular compromise- >60 severe pain, shock, circulatory collapse• Respiration- 12-16 normal, does not rule out disease- >24 pain, increase due to visceral distension with gas or

fluid- Acid base imbalance due to electrolyte loss- Hypoxia due to cardiovascular collapse

• Mucus membranes- Color- Hydration, moist vs tacky- Capillary refill timea. <2 sec normalb. >2 sec, delayed, >4 severe cardiovascular

collapse

• Abdominal auscultation- presence or absence of gut sounds

• Pain assessment/characterization- Intermittent vs constant- Severity- Response to analgesics

• Rectal exam by vet• Nasogastric reflux- quantity, color/odor, ph• Abdominocentesis- belly tap- Total protein- Cellularity- Bacteria• PCV or hemocrit

Treatment for colic

• Surgical treatment of a medical case is highly counterproductive

• Medical treatment of a surgical case of colic is fatal

Medical treatment

• Fluid management- gallons IV, fluid of body trapped in intestines due to no reabsorption, monitor PCV for overhydration

• Pain managementa. Banamine- NSAID- Potent analgesic, can mask surgical colic, - Binds endotoxins, - PO, IV, IM

b. Phenylbutazone- NSAID- Contraindicated in GI disorders- Associated with ulceration of GI tract- PO, IV, never IM or SQ

c. Xylazine ( rompun)- Potent sedative and analgesic- IV or IMd. Butorphanol ( torbugesic)- Potent analgesic, some degree of sedation- IV- Controlled substance

e. Detomidine ( dormesedan)- Potent sedative and analgesic- IV

Return of GI function

• Lubricants, surfactants, cathartics- Mineral oil, lubricants- DSS dioctyl sodium succinate, surfactant- Magnesium sulfate ( epsom salt) cathartic• Intestinal protectants- Kaolin pectin- Pepto bismol useful in diarrhea, 1ml/lb every

4-6 hours

• Antibiotics?- Judicious selection due to gut permeability

and altered flora- Don’t use oral with compromised gut function

Surgical correction• Correct displacement• Decompression• Enterotomy• Resection and anastomosisPost surgical complications- Abdominal wall herniation- Peritonitis- Adhesions, stenosis- Chronic malabsorptive disorder- Chronic diarrhea, soft feces- Founder ,laminitis- Chronic recurrent colic

Equine Diseases

• Rabies- virus, infects CNS- Transmitted when bitten by infected animal- Signs: inability to swallow, colic, abnormal

behavior, “just not right”- Prev: vaccination- TX: noneNOTE: assume rabies first

• Equine Viral Rhinopneumonitis- Signs- may abort, mild upper respiratory disease, watery discharge- prev: vaccination, must be repeated because

the vaccine has a short duration, during pregnancy vaccinate at 5, 7, 9 month

- TX: supportive

• Equine influenza- Viral disease- Trans: inhale infective material in droplets- Signs: sudden fever, weak, cough with watery

discharge from nose

• Tetanus- Cl. Tetani invades an open wound- Signs: muscle spasms, sawhorse, 3rd eyelid

protrudes, nervous- Tx: none- Prev: vaccination

• Lyme disease- Borrelia burgodorferi- Signs: fever, lameness, swollen joints, - Dx: signs, blood tests, history of ticks- Tx: antibiotics and antiinflammatory- Prev: tick control

• Equine Infectious anemia ( swamp fever)- Viral disease of horses- Signs: anemia, fever, weakness, eventual

weight loss, legs swell, lower abdomen swell- DX: Coggins test ( necessary for sale,

movement of horses) REPORTABLE- Trans: horse flies, mosquitos, lice- TX: none, euth, isolation

• Strangles- Streptococcus equi- Signs: throat swelling, infection, fever, abscess

in mandibular lymph nodes- Trans: secretions from abscess- Tx: penicillin until abscesses dry up

• Equine protozoal myeloencephalitis- Sarcocystis neurona- Signs: ataxia- Trans: ingest parasite in feed- Tx: NSAIDS, DMSO- DX: western blot test

• Eastern Equine Encephalitis- Viral- Trans: mosquitoes- Signs: behavior change, unsteady, seizures and

death- Tx: none- Venezuelan and Western EE as well

• Vesicular Stomatitis- viral, resembles foot and mouth- Trans: ?- Signs: ulcers, blisters in mouth- TX: supportive - DX: isolate virus from lesion- REPORTABLE

• Navicular disease- Ulcer on navicular bone in foot,- Caused by surface, shoeing problems,

heritable- Signs: won’t put weight on heel, toe walker- Tx: shoes and soft ground

• Potomac horse fever- Bacterial Ehrlichia risticii- Trans: arthropods- Signs: slight fever, anorexia progresses to high

fever, projectile watery diarrhea for 10 days- DX: antibody test- Prev: vaccination

• Equine viral arteritis- Viral- Signs: swelling of lower legs, abdomen,

sheath, mm of eyes, nasal discharge, fever- Prev: vaccination

• West Nile Virus- Viral- Signs: ataxia of rear legs and eventually go

down- Trans: mosquitoes- Prev: vaccination

• Chronic obstructive Pulmonary disease COPD- Reaction to fungal spores on hay or straw- Signs: roaring, heave line- TX: steroids, inhalants, injectables

• Neurologic Equine Herpes Virus- Equine herpes virus- Signs: respiratory illness, fever, nasal

discharge, cough- 80% of horses over 2 are carriers- Shed when stresses

• Neurologic syndrome of EHV- weakness, ataxia, hind end paralysis- Mutation led to neurologic form- Restrictions placed on horse travel- 30-50% euthanized- Shed virus in nasal secretions- Quarantined farms

• EHV vaccination- Killed vaccine does not prevent neurologic

form- Modified live vaccine, Rhinoimmune, may

protect from neurologic form- Rhinoimmune recommended for exposed and

stressed horses, every 90 days with events or 3, 5,7 , 9 mo. of pregnancy

• Founder/laminitis- causes: toxemia, carbohydrates, trauma, - Signs: lameness- DX: stance, pulses, hoof testers at toe, rads- Tx: address cause, shoeing, NSAIDS

• Wobbler Syndrome- Cervical vertebral instability- Young 4-24 months, rapidly growing- DX: history, neuro exam, rads, myelography- TX: stabilize vertebra, euth

• Tying up, Rhabdomyolsis, Monday morning disease

- Cause: high grain diet, over exercise, no cool down

- Signs: stiff, sore gait, sweating- Dx: serum CPK, myoglobinuria- Tx: NSAIDS, rest,

• Idiopathic Laryngeal hemiplegia (roaring)- Paralysis of left side of larynx- Signs: exercise intolerance, inspiratory noise- Dx: history, signs, atrophy of laryngeal muscle- TX: depends on use, surgery

• Exercise induced pulmonary hemorrhage- Rupture of blood vessels in lungs- Throroughbreds, standardbreds- cause: trauma, exercise- Dx: epistasis post exertion- TX: furosemide, blood pressure meds

• Sarcoid- Neoplasia or viral- Signs: ulcerated nodular mass on trunk/neck- Tx: immunotherapy, surgical debridement

• Melanoma- Neoplasia of gray horses- On perineum, penis, muzzle, periocular- Dx: presentation- TX: cryosurgery, cimetidine

• Proud Flesh- Granulation tissue out of control, usually on

lower limbs- Tx: topical digestive enzymes, trypsin, surgical

excision and skin grafts

• Recurrent uveitis, moon blindness, periodic opthalmia

- Cause unknown or leptospirosis- Signs: red, painful eye, conjunctivitys, tearing,

blepharospasm, anterior chamber cloudy, +/- cataract, - corneal stain

- Tx: topical corticosteroids