ANS 2160 Equine Science Exam 2

Muscular system

Muscular, cardiovascular, respiratory, skeletal, and nervous systems work together to make the horse an efficient performer.

Athleticism in horses

Large heart, high oxygen-carrying capacity, efficient lungs tied to stride rhythm, and muscle fiber diversity make horses especially athletic compared to other animals.

Types of muscle tissue

Smooth (involuntary organs), cardiac (heart), skeletal (voluntary movement).

Types of muscle fibers

Type I (slow-twitch), Type IIA (fast oxidative), Type IIB (fast glycolytic).

Endurance muscle fiber type

Type I - slow-twitch, aerobic, fatigue resistant.

Sprinting muscle fiber type

Type IIB - fast-twitch glycolytic, anaerobic, fatigues quickly.

Cause of muscle fatigue

Lactic acid buildup from anaerobic metabolism and depletion of energy stores.

Aerobic vs anaerobic metabolism

Aerobic uses oxygen (long-term energy, CO₂ + H₂O), anaerobic does not (short-term energy, lactic acid).

Energy fuels for horses

Glucose, glycogen, and fatty acids.

Anaerobic metabolism usage

During short, intense bursts like galloping or jumping.

Aerobic metabolism usage

During long, moderate exercise like endurance or trail riding.

Cardiac output formula

Amount of blood pumped per minute = Heart Rate × Stroke Volume.

Normal resting heart rate for a horse

28-45 bpm.

Maximum heart rate during intense exercise

Around 240 bpm.

Spleen function during exercise

It contracts, releasing stored red blood cells to increase oxygen capacity.

Importance of spleen function

It doubles red blood cell count and boosts aerobic performance.

Tidal volume (TV)

The amount of air inhaled/exhaled per breath.

Minute volume (MV)

Total air per minute = Tidal Volume × Respiratory Frequency.

Locomotor-respiratory coupling (LRC)

Breathing is synchronized with stride; one breath per stride at gallop.

LRC performance benefit

Increases oxygen efficiency and reduces fatigue.

Roaring in horses

Laryngeal hemiplegia — partial paralysis of the larynx causing noisy breathing.

Heaves

COPD/RAO — chronic airway inflammation from allergens or dust.

EIPH

Exercise-Induced Pulmonary Hemorrhage — bleeding in the lungs during intense exercise.

Cooling methods for horses

Sweating (with latherin protein) and increasing blood flow to the skin.

Signs of heat stress or fatigue

Heavy sweating, uncoordinated movement, dehydration, high heart rate.

Replacement after heavy sweating

Water and electrolytes (Na, Cl, K).

Goals of a conditioning program

Improve cardiovascular fitness, strength, endurance, and recovery.

Signs of good conditioning

Lower resting HR, quick recovery, calm behavior, steady appetite.

Signs of fatigue

Excessive sweating, long recovery, stiffness, and poor performance.

Conditioning effect on metabolism

Increases use of fat for energy, decreases lactic acid buildup, improves oxygen efficiency.

Horse's monocular field of vision

About 215° per eye — great for detecting movement.

Horse's binocular field of vision

Around 60-70°, where depth perception is best.

Colors horses can see

Blue and yellow (they are dichromatic).

Horse's hearing range

33 Hz - 55 kHz (much higher than humans).

Rotation of the auricle (ear)

Helps the horse locate the direction of a sound.

Olfactory receptors in horses

About 300 million (humans have 5-6 million).

Vomeronasal organ

Used for detecting pheromones — especially during the Flehmen response.

Sensitive areas of a horse

Eyes, lips, ears, nose, withers, ribs, flanks, and legs.

Horse's snort

Usually indicates alarm or danger.

Whinny or neigh

Means distress or calling to other horses.

Nicker

A friendly greeting, care, or courtship.

Ear position

Forward = alert; pinned = anger or aggression.

Flaring nostrils and wide eyes

Usually mean fear, excitement, or heightened alertness.

Harem group

One stallion with several mares and foals.

Bachelor group

A group of young or non-breeding males.

Dominance in horses

Shown by controlling the movement of others (not always through aggression).

Ingestive behavior

Eating and drinking behaviors.

Eliminative behavior

Defecating or urinating — may mark territory.

Contactual behavior

Seeking affection or protection — e.g., huddling.

Sexual behavior

Acts of courtship and copulation (Flehmen, teasing).

Epimeletic behavior

Giving care or attention (mutual grooming).

Et-epimeletic behavior

Seeking care or attention (foal calling for dam).

Allelomimetic behavior

Mimicry — one horse copies another's action.

Investigative behavior

Exploring or inspecting new objects or surroundings.

Agonistic behavior

Related to conflict or fighting (aggression/submission).

Dominance behavior

Establishing hierarchy or control in a group.

First line of defense for horses

Flight.

Using fight instead of flight

Occurs when a horse can't escape (confined space).

Precocial

Foals are able to stand and move soon after birth.

Override of hunger or fatigue

Self-preservation instinct.

Time spent eating by horses

About 60% of the day.

Daily travel distance for horses

Up to 6 miles per day.

Effect of stalling on time budgets

They stand more and eat less → can lead to stress or vices.

Causes of stereotypical behaviors (vices)

Boredom, stress, isolation, frustration, anticipation.

Dangerous vices to humans

Biting, rearing, striking.

Dangerous vices to the horse

Cribbing, weaving, stall walking.

Cribbing

Grasping an object with teeth and sucking air — releases endorphins.

Reducing vices

More turnout, social contact, and roughage (fiber).

Stimulus (cue)

A signal that triggers a specific response.

Response

The horse's action following a cue.

Reinforcement

Anything that strengthens the desired response.

Positive reinforcement

Adding a pleasant reward (e.g., pat, kind voice).

Negative reinforcement

Removing an unpleasant stimulus (e.g., releasing pressure).

Punishment

Adding an unpleasant stimulus to discourage a behavior.

Shaping behavior

Rewarding small steps toward the desired response.

Importance of timing in training

The horse must associate the reward or consequence immediately with the behavior.

Acquisition

Continuous reinforcement, fast learning.

Extinction

No reinforcement → behavior fades.

Reinforcement schedule for advanced horses

Intermittent reinforcement.

Responses to stress

Habituation, development of abnormal behavior, or permanent fear memory.

Natural stress management for horses

Social contact, adequate exercise, fiber-rich diet, and consistent routines.

Main parts of the mare's reproductive tract

Vulva, vagina, cervix, uterus, oviducts, ovaries, uterotubal junction (UTJ).

Vulva during estrus

Loose, relaxed, winking.

Vulva during diestrus

Tight, closed.

Problems caused by poor perineal conformation

Windsucking and uterine infections.

Cervix during estrus

Soft, open, watery mucus.

Cervix during pregnancy

Tight, sticky plug.

Type of uterus in a mare

Bipartite (a type of bicornuate) with two short uterine horns.

Fertilization location

In the ampulla of the oviduct.

Structure catching the ovum after ovulation

Infundibulum.

Function of the uterotubal junction (UTJ)

Controls sperm entry, acts as a sperm reservoir.

Unique feature of the mare's ovary

Ovulation only occurs at the ovulation fossa.

Functions of the ovary

Exocrine: Produce ova; Endocrine: Secrete hormones (estrogen, progesterone).

Hormone produced by follicles

Estrogen — causes mare to show heat and relax cervix/uterus.

Structure formed after ovulation

Corpus hemorrhagicum (CH), which becomes the corpus luteum (CL).

Hormone secreted by the corpus luteum

Progesterone — maintains pregnancy and makes the mare unresponsive to stallion.

CL if the mare is not pregnant

The uterus releases PGF2α, lysing the CL → cycle restarts.

Average length of the mare's estrous cycle

21 days (estrus 5-7 days, diestrus 14-16 days).

Breeding type of the mare

Seasonal polyestrous — cycles in spring/summer, stops in winter.

Hormonal trigger for cycling to start

Increased daylight → ↓ melatonin → ↑ GnRH → ↑ FSH & LH.