The Equine Digestive System IMS #8895-A. Objectives Discuss internal organs Discuss internal organs...

The Equine Digestive The Equine Digestive SystemSystem

IMS #8895-AIMS #8895-A

ObjectivesObjectives

Discuss internal organsDiscuss internal organs

Identify the structures of the digestive Identify the structures of the digestive systemsystem

Recognize functions of the organs Recognize functions of the organs comprising the digestive system comprising the digestive system

Digestive SystemDigestive System

Monogastric - having one stomachMonogastric - having one stomach

Herbivores - plant-eating animals Herbivores - plant-eating animals

Digestive system anatomically developed Digestive system anatomically developed to continually digest small amount of food to continually digest small amount of food


Eat simple-looking feeds containing Eat simple-looking feeds containing complex chemical substances complex chemical substances

dramatic changes during digestive process dramatic changes during digestive process before feed is used as energybefore feed is used as energy

Digestion - process of mechanical and Digestion - process of mechanical and chemical breakdown of feed into simple chemical breakdown of feed into simple structuresstructures


Simple structures are:Simple structures are:solublesoluble (able to be dissolved) in water (able to be dissolved) in water

absorbed through absorbed through mucous membranesmucous membranes lining lining intestinal tractintestinal tract

membranes that line cavities in the body and membranes that line cavities in the body and connects inside of cavity to outsideconnects inside of cavity to outside


Unique Unique

Small, efficient stomach for grain utilizationSmall, efficient stomach for grain utilization

Large cecum and colon for roughage Large cecum and colon for roughage utilizationutilization


Purpose - process feed into component Purpose - process feed into component nutrients for:nutrients for:

AbsorptionAbsorption - process of taking in by various - process of taking in by various means means

UtilizationUtilization


Alimentary canal (digestive system) - Alimentary canal (digestive system) - muscular hollow tube beginning at mouth muscular hollow tube beginning at mouth and ending at anus and ending at anus

Loops on itself many timesLoops on itself many times

Size - One inch in diameter at small Size - One inch in diameter at small intestine to eight inches at large colonintestine to eight inches at large colon

Digestive SystemDigestive SystemComponent parts include:Component parts include:MouthMouthPharynxPharynxEsophagusEsophagusStomachStomachSmall intestineSmall intestineLarge intestineLarge intestineRectumRectumAnusAnus


Large intestine consists of the:Large intestine consists of the:

CecumCecumVentral and dorsal colonVentral and dorsal colonTransverse colonTransverse colonSmall colonSmall colonRectum Rectum


Alimentary tract with help of teeth, tongue, Alimentary tract with help of teeth, tongue, salivary glands, liver, and pancreas salivary glands, liver, and pancreas prepare feed for absorption and eliminates prepare feed for absorption and eliminates wastewaste

Few feeds eaten are in simple forms ready Few feeds eaten are in simple forms ready to be absorbed and utilizedto be absorbed and utilized

Digestive SystemDigestive SystemMost feeds require substantial change by:Most feeds require substantial change by:Mechanical ActionMechanical Action

Secretory Action - products produced by Secretory Action - products produced by glands that aid in digestionglands that aid in digestion

Chemical ActionChemical Action

Microbial Action - digestion by very minute Microbial Action - digestion by very minute organismsorganisms


Mechanical actions include:Mechanical actions include:Mastication – chewingMastication – chewing

Deglutition – swallowingDeglutition – swallowing

Intestinal movementsIntestinal movements

Defecation - elimination of wasteDefecation - elimination of waste

Anatomy of the Digestive Anatomy of the Digestive SystemSystem

MouthMouth

First section of alimentary canalFirst section of alimentary canal

Contains 24 molars and 12 incisorsContains 24 molars and 12 incisors

Includes tongue and salivary glandsIncludes tongue and salivary glands

MouthMouth

Prehension -the grasping and moving of Prehension -the grasping and moving of feed into the mouth by a sensitive, mobile feed into the mouth by a sensitive, mobile upper lipupper lip

Precise - can graze grass almost into Precise - can graze grass almost into groundground

Sorts and selects haySorts and selects hay

MouthMouth

Digestion - begins in mouth when feed is Digestion - begins in mouth when feed is masticatedmasticated by the teeth by the teeth

grinded and chewed by the mouthgrinded and chewed by the mouth

Serves to reduce feed particle size Serves to reduce feed particle size

MouthMouth

Saliva:Saliva:85 pounds (10 gallons) daily85 pounds (10 gallons) daily

Wets feed - Easier to pass through Wets feed - Easier to pass through esophagusesophagus

Enzymes - help digest carbohydratesEnzymes - help digest carbohydrates

Produce large amounts only while chewingProduce large amounts only while chewing

PharynxPharynx

MuscularMuscular

Funnel shapeFunnel shape

Guides feed into esophagusGuides feed into esophagus

Located in upper back of mouth where Located in upper back of mouth where digestive and respiratory tracts crossdigestive and respiratory tracts cross

PharynxPharynx

Once feed or water enters pharynx, it Once feed or water enters pharynx, it cannot return because of blocking action cannot return because of blocking action of soft palateof soft palate

Epiglottis closes at the same time to Epiglottis closes at the same time to prevent feed from entering lungsprevent feed from entering lungs

EsophagusEsophagus

4 to 5 feet in length4 to 5 feet in length

Extends from mouth down left side of Extends from mouth down left side of neck, through the diaphragm, and to the neck, through the diaphragm, and to the stomachstomach

Moves feed and water to stomach by Moves feed and water to stomach by progressive waves of muscular progressive waves of muscular contractions called peristalsis contractions called peristalsis

EsophagusEsophagus

Waves irreversibleWaves irreversible

Extreme muscle tone occurs at end of Extreme muscle tone occurs at end of esophagusesophagus

EsophagusEsophagus

Extremely difficult to expel gases through Extremely difficult to expel gases through eructationeructation the act of expelling gas from the stomach the act of expelling gas from the stomach

through the mouththrough the mouth

Stomach would rupture before vomiting Stomach would rupture before vomiting would occurwould occur

StomachStomach

U-shaped sac near diaphragm at front of U-shaped sac near diaphragm at front of abdominal cavityabdominal cavity

Sphincter acts as powerful muscle where Sphincter acts as powerful muscle where esophagus enters into stomachesophagus enters into stomach

Makes vomiting nearly impossibleMakes vomiting nearly impossible

StomachStomach

Small compared to other animalsSmall compared to other animals

10% of total capacity of entire digestive 10% of total capacity of entire digestive tracttract

Capacity - two to four gallons Capacity - two to four gallons requires they eat two to three times daily requires they eat two to three times daily

rather than just oncerather than just once

StomachStomach

Feed moves through rapidlyFeed moves through rapidly

Frequent feeding in small amounts is more Frequent feeding in small amounts is more efficient and better satisfiesefficient and better satisfies

Rate of passageRate of passage is rapid in comparison to is rapid in comparison to other areasother areasTime required for something to move through Time required for something to move through

an areaan area

StomachStomach

Reservoir for ingested feed while Reservoir for ingested feed while subjecting it to subjecting it to gastric digestiongastric digestion chemical breakdown of feedstuffs by the chemical breakdown of feedstuffs by the

stomachstomach

Gastric juices, secreted by glands in the Gastric juices, secreted by glands in the mucous membrane of stomach, contain mucous membrane of stomach, contain hydrochloric acid, pepsin & gastric lipasehydrochloric acid, pepsin & gastric lipase

StomachStomach

Pepsin is a protease - enzyme that helps Pepsin is a protease - enzyme that helps digest protein into digest protein into amino acidsamino acidsbuilding blocks of proteinsbuilding blocks of proteins

Gastric lipase - digest fat into fatty acids & Gastric lipase - digest fat into fatty acids & glycerolglycerol

StomachStomach

When two-thirds full, feed passes into When two-thirds full, feed passes into small intestine and continues as eating small intestine and continues as eating continuescontinues

If horse eats too much at one time, some If horse eats too much at one time, some

will leave stomach without sufficient will leave stomach without sufficient digestive action digestive action Leads to decreased efficiency Leads to decreased efficiency

StomachStomach

Number of digestive disorders can occurNumber of digestive disorders can occur

Caused by:Caused by:moldy feedsmoldy feedsground mashesground mashessudden changes in feedsudden changes in feed feast-and-famine situationsfeast-and-famine situationsparasitesparasites

StomachStomach

Very little nutrient absorption takes place Very little nutrient absorption takes place in the stomachin the stomach

Proteins and carbohydrates are only Proteins and carbohydrates are only partially digestedpartially digested

Small IntestineSmall Intestine

2 inch by 60 foot tube2 inch by 60 foot tube

Holds approximately 12 gallonsHolds approximately 12 gallons

Connects stomach to large intestine Connects stomach to large intestine

Contains three parts: the duodenum, the Contains three parts: the duodenum, the jejunum, and the ileum jejunum, and the ileum


30% of the digestive tract30% of the digestive tract

Folded into many loops and coils Folded into many loops and coils

2.5 to 4 hours for feed to pass2.5 to 4 hours for feed to pass


BloodwormsBloodwormscause blood clots cause blood clots

may result in colic or deathmay result in colic or death

tend to lodge in the mesentery artery tend to lodge in the mesentery artery which supplies blood to the intestineswhich supplies blood to the intestines


Small intestine and accessory organs, the Small intestine and accessory organs, the pancreas and liver, supply enzymespancreas and liver, supply enzymes

Peristalsis mixes fluid contents of the Peristalsis mixes fluid contents of the

which are about 92-95% waterwhich are about 92-95% water

Pancreatic juices contain the enzymes Pancreatic juices contain the enzymes trypsin, pancreatic lipase, and amylasetrypsin, pancreatic lipase, and amylase


Trypsin - converts proteins into amino Trypsin - converts proteins into amino acids which the small intestine absorbsacids which the small intestine absorbs

Primary site of protein digestion and Primary site of protein digestion and absorption of amino acidsabsorption of amino acids

Pancreatic lipase - breaks down fats to Pancreatic lipase - breaks down fats to glycerol and fatty acids glycerol and fatty acids


Liver secretes bile Liver secretes bile helps break down fathelps break down fataids in fatty acid absorptionaids in fatty acid absorptionactivates pancreatic lipaseactivates pancreatic lipase

Most soluble carbohydrates digested in Most soluble carbohydrates digested in small intestinesmall intestine


End products of carbohydrate digestion End products of carbohydrate digestion are glucose and volatile fatty acids which are glucose and volatile fatty acids which are absorbed for energyare absorbed for energy

Absorbs nutrients, such as simple sugars, Absorbs nutrients, such as simple sugars, fatty acids, amino acids, minerals, and fatty acids, amino acids, minerals, and vitaminsvitamins

Large IntestineLarge Intestine

Composed of the cecum, large colon, Composed of the cecum, large colon, small colon, and rectumsmall colon, and rectum

Moves undigested materials from small Moves undigested materials from small intestine to anus for eliminationintestine to anus for elimination

50-60% of digestive tract50-60% of digestive tract


Holds 30-35 gallonsHolds 30-35 gallons

25 feet long25 feet long

Designed for utilization of plant fiber for Designed for utilization of plant fiber for energyenergy


After After ingestaingesta leaves small intestine, it leaves small intestine, it enters into cecumenters into cecumsubstances that have been taken into the substances that have been taken into the

body by way of the digestive tractbody by way of the digestive tract

Cecum serves as fermentation vat in Cecum serves as fermentation vat in

which enzymes break down fibrous plant which enzymes break down fibrous plant structures for digestionstructures for digestion

Large IntestineLarge IntestineCarbohydrates such as Carbohydrates such as cellulosecellulose that that

escaped digestion in small intestine are escaped digestion in small intestine are fermented in large intestinefermented in large intestine

Complex carbohydrate that is the main Complex carbohydrate that is the main component of the plant cell wallcomponent of the plant cell wall


Can digest cellulose, starch, & sugars into Can digest cellulose, starch, & sugars into volatile fatty acids volatile fatty acids

supplies up to 25% of horse’s energysupplies up to 25% of horse’s energy


Cecum - primary site of water absorptionCecum - primary site of water absorption

Rate of passage slower than in other Rate of passage slower than in other portions of digestive tractportions of digestive tract

36-48 hours36-48 hours

RectumRectum

Connects small colon to anusConnects small colon to anus

Receives feces small colon has formed Receives feces small colon has formed into characteristic ballsinto characteristic balls

Forty to fifty pounds of feces is voided Forty to fifty pounds of feces is voided eight to twelve times a dayeight to twelve times a day

RectumRectum

Shape, size, and consistency of feces give Shape, size, and consistency of feces give clues to overall healthclues to overall health

Dry and hard - lack of water or proteinDry and hard - lack of water or protein

Too soft - Sick or eating diet that is too Too soft - Sick or eating diet that is too laxative laxative

Digestive System DisordersDigestive System Disorders

DisordersDisorders

Because of the complex nature of the Because of the complex nature of the digestive system, horses are predisposed digestive system, horses are predisposed to digestive disordersto digestive disorders

Susceptible to twisting and impaction of Susceptible to twisting and impaction of the large intestinethe large intestine

DisordersDisorders

Sensitive to gases produced by microbial Sensitive to gases produced by microbial digestiondigestion

Rapid fermentation may cause excessive Rapid fermentation may cause excessive gas or lactic acid to be producedgas or lactic acid to be produced

can cause colic or laminitiscan cause colic or laminitis

ColicColic

““Colic” - many painful digestive Colic” - many painful digestive disturbances with various causesdisturbances with various causes

Improper feeding such as feeding too Improper feeding such as feeding too much grain or suddenly changing the diet much grain or suddenly changing the diet can cause coliccan cause colic

ColicColic

Usually caused by gaseous products that Usually caused by gaseous products that are part of microbial digestionsare part of microbial digestions

May cause swelling in digestive tractMay cause swelling in digestive tract

Ingesting low quality, poorly digestible Ingesting low quality, poorly digestible feed can cause impaction of cecum and feed can cause impaction of cecum and colon colon

ColicColic

To avoid digestive disturbances, allow one To avoid digestive disturbances, allow one to two weeks to change from one feed to to two weeks to change from one feed to another.another.

LaminitisLaminitis

Occurs when inner hoof wall becomes Occurs when inner hoof wall becomes inflamedinflamed

Rapid changes in diet can cause certain Rapid changes in diet can cause certain type of bacteria in cecum to dietype of bacteria in cecum to die

Release large amounts of endotoxins Release large amounts of endotoxins

LaminitisLaminitis

Endotoxins enter bloodstream and Endotoxins enter bloodstream and decrease the amount of blood flow to decrease the amount of blood flow to laminalamina

Commonly occurs when a horse is Commonly occurs when a horse is switched from winter hay to pasture in the switched from winter hay to pasture in the spring spring

SummarySummary

Purpose of digestive system is to process Purpose of digestive system is to process feed into component nutrients for feed into component nutrients for absorption and utilization by the bodyabsorption and utilization by the body

Very complexVery complex

Many digestive disordersMany digestive disorders

SummarySummary

MonogastricMonogastric

Eat relatively simple-looking foods that are Eat relatively simple-looking foods that are transformed to an easily digestible formtransformed to an easily digestible form

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part, of this presentation withoutwritten permission is prohibited.

Instructional Materials ServiceTexas A&M University

2588 TAMUSCollege Station, Texas 77843-2588

http://www-ims.tamu.edu

2008

The Equine Digestive System IMS #8895-A. Objectives Discuss internal organs Discuss internal organs...

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