Equine Science Exam 4 FINAL EXAM

foot

foundation of the horse, most common area of forelimb lameness

biological structures

bone, soft tissue, hoof capsule

coffin bone

3rd phalanx

short pastern bone

2nd phalanx

navicular bone

distal sesamoid

joints

coffin, pastern, fetlock

blood vessels

medial and lateral, digital arteries, digital veins

superficial external structures

hoof wall, coronary band, frog, sole, white line, bars

sole

concave, protection, plays a role in concussion, not meant to bear a lot of weight

bars

weight bearing, additional heel strength, allows lateral movement

navicular bone

focal point for disease, coupled with the digital flexor tendon makes the joint elastic and yielding; thus counteracting shock

front of leg tendons

extensor tendons, extend forward

back of leg tendons

flexor tendons, flex back

functional foot

weight bearing structures and soft tissue structures of the foot are intact, healthy, and compliment each other

shoes

provide protection, decrease energy absorption, alter pattern of wear, influence movement

horse’s weight on front legs

2/3

lameness on the front

78%

hoof growth

coronary band down, ~1/4 inch per month

hoof wall

thinnest at heel

sole

3/8 inches thick

frog

protects the foot and aids in traction, absorbs shock and concussion

comfort zone angles of front and back feet

48-55 degrees

lower angle =

more stress on tendons and ligaments, makes horse trip more

to raise angle

take more toe and leave more heel

to lower angle

take more heel and leave more toe

extremely low angles

slow time of breakover, linked to navicular syndrome and strained DDFTs

extremely high angles

speed up breakover time, linked to abnormal loading of coffin joint surfaces, injury to extensor process, increased strain to suspensory ligaments

balance

most important factor in equine podiatry

goal of hoof trimming

make hoof wall level, and pastern, shoulder, and hoof angles all parallel

Duckett’s Dot/Bridge

widest part of foot, rest of foot is centered around it

2/3 of foot

should be behind the apex of the frog

1/3 of foot

should be in front of the apex of the frog

mediolateral balance

ensures load bearing is as uniform as possible, begins with having heel lengths the same on each side of the foot

types of trim

pasture trim, light use trim, trimmed for shoe

pasture trim

really round toe

light use trim

45 degree halfway off the wall from quarter to quarter

shoe trim

flat

if trimmed before 2 years of age

can help correct conformational deviations

if trimmed after 2 years of age

just hides conformational deviations

purpose of shoes

protection, support, traction, and performance

3 point contact

toe region and both heels

shoe modifications

roll, rocker, square toe

squaring toe =

shorter stride, prevents clipping themselves and pulling shoes

roll or rocker

decreases stride length

clips

stabilize shoe, aids in retention of shoe, prevents shoe from shearing off at the nails

coronary circumference

78 lb/in² body weight to hoof area ratio

kinesiology

study of movement

kinematics

describes motion without consideration of what makes it happen

kinetics

forces that produce movement

electromyography

relationship between force and electrical activity of the muscle

stride

complete cycle of limb movements

phases of stride

stance, break over, swing

stance

impact → right after foot hits the ground, loading → limb loaded gradually, fetlock extends

break over

starts when heel leaves ground, finishes when toe leaves ground

swing

time the foot is in the air

balance

the ability to keep the center of mass within the limits of the base of support

proprioception

most important factor of balance

general observations for lameness

conformation, symmetry, stance, muscling

visual evaluation at rest

stall posture, muscle symmetry, conformation, hoof balance

dynamic exam

gait evaluation, footing, multiple surfaces, straight and in a circle

hoof evaluation

overall evaluation of the foot, symmetry, hoof wear, shoeing

forelimb lameness observations

head nod, down on sound up on lame, tensing of shoulder, alterations in height of foot flight arc, length of stride, joint flexion angles, degree of fetlock drop, sound differences

hindlimb lameness observations

hip hike, excess vertical displacement of tuber coxae or croup, drifting, length of stride, reduced flexion of joints

grading lameness

0-5

lameness grade 0

no lameness

lameness grade 1

difficult to see, not consistent

lameness grade 2

difficult to see at walk or trot in straight line, consistent under certain circumstances

lameness grade 3

consistently seen at trot under all circumstances

lameness grade 4

obvious at walk

lameness grade 5

minimal or non weight bearing

front limb flexions

distal limb, carpal, elbow, shoulder flexion

hind limb flexions

distal limb, stifle, full limb/hock flexion

diagnostic analgesia

used to localize lameness, local infiltration, regional blocks, nerve blocks, intra-articular

radiographs

diagnose acute trauma and bone disease

ultrasounds

soft tissue injuries

nuclear scintigraphy

bone scan, administration of radiopharmaceutical, highly sensitive, low specificity

animal rights

philosophical view that animals have rights similar or the same as humans

main players of animal rights

Humane Society of the United States and PETA

animal welfare

emphasizes human treatment of animals, animals can be used to benefit humans, use of animals is essential but animals should be made as happy and comfortable as possible

breeding

process of evaluating and selecting animals for production of offspring

genetics

the study of heredity and the variation of inherited characterstics

variation

a different or distinct form or version of something

parts of genetics

transmission, molecular, quantitative, population

transmission

how genes are inherited from parents to offspring

molecular

how genetic info is encoded and expressed

quantitative

how multiple factors interact to produce complex phenotypes

population

how genes impact populations

zygosity

the relationship between the 2 copies of genetic information in the cell

multiplication rule

if 2 events are independents then p(A and B) = p(A) x p(B)

addition rule

if 2 events are mutually exclusive then p(A or B) = p(A) + p(B)

mendel’s laws of inheritance

segregation, dominance, independent assortment

exceptions to mendel’s rules

incomplete penetrance, sex influenced traits, sex linked traits, sex limited traits

incomplete penetrance

individual possesses a particular genotype, but the associated phenotype is not expressed

can result from secondary genetic influences on expression, environment, random effects

sex influenced traits

traits in which the same genotype is associated with different phenotypes depending on the gender

can be size, color, behavior, or morphology

sex linked traits

the pattern of inheritance for genes located on sex chromosomes

example colorblindness on the x chromosomes in humans

sex limited traits

traits where phenotypic expression is limited to only one gender

example milk production in mares

HERDA - hereditary equine regional dermal asthenia

horses present with fragile, thin skin which has slow healing and scarring

HERDA details

skin decrease in tensile strength, environmental factors make it worse, average presentation is 1.5 years, majority is AQH, not sex-linked, impacts collagen

HYPP - hyperkalemic periodic paralysis

horses present with sudden unexplained muscle twitches, sudden collapse, temporary paralysis, muscle weakness, heart arrhythmia

HYPP details

high levels of patassium in plasma, attacks precipitated by rest following exercise and fasting, can be triggered by sedation, average age of presentation is 2-3 years, majority AQH, not sex linked, impacts sodium channel