Herbivore Digestive Anatomy

Integrated Rangeland Management REM 456

Spring 2013Sergio Arispe, Ph.D.

http://www.lelylife.com http://horsetrailerworld.com

OverviewComparative Digestive Anatomy

Herbivory

Digestive Systems

Anatomy

Digestive End-Products

Foregut Fermenters

Comparative Digestive Anatomy

http://yr11-biology-revision.wikispaces.com

Fraction of Primary Production Consumed By Various

HerbivoresFRACTION VEGETATION TYPE HERBIVORE

GRASSLANDS INVERTEBRATES30-60% GRASSLANDS

GRASSLANDS (AFRICA)

UNGULATES20-90% TUNDRA

GRAMINOIDSTALLGRASS PRAIRIE BIRDS (GRANIVORES)58% SALT MARSH

(Modified from Crawley, 1983)

Herbivory

Cellulose

β-1,4 linkages

Herbivory

α-1,4 linkages and α-1,6 linkagesMaltose

Amylose

Digestive Systems

The major purpose of the digestive system is to provide for the assimilation of nutrients required for biological functions including maintenance, growth, lactation, and reproduction

Digestive SystemsNon-cellulose digestors Hindgut or Post-gastric FermentersForegut or Pre-gastric FermentersArchitecture of GIT

Location, size, and shape

Nature and location of the digestive agentsEnzymes and digestive juices, fermentation

Chemical nature of the end products of digestionAmino acids, Volatile Fatty Acids (VFA’s), Monoacylglycerol (MAG), Free Fatty Acids (FFA)

Gastrointestinal Tract (GIT) Functions

Diet

Esophagus

Stomach

Large IntestineAnus

Origins of Simple Stomach Animals

(Van Soest, 1994)

Non-cellulose Digestors

Simple stomach animals (Monogastrics)

E.g., Humans, swine, reptiles

Cellulose is not an energy source

(Van Soest, 1994)

Cellulose DigestorsHindgut Fermentors

Foregut Fermentors

www.tamu.edu

Hindgut FermentersDiet

MouthEsophagus

Stomach

Small Intestine

Large Intestine

AnusColon

Cecum

Hindgut FermentersCecal Fermenters

E.g., Rabbits, Guinea Pigs, Rat

http://www.rabbitfood.org.uk(Stevens, 1977)

Hindgut FermentersCecal Fermenters

Rabbits, Guinea Pigs, RatDiet

MouthEsophagus

Stomach

Small Intestine

Large Intestine

FecesColonCecum

http://www.rabbitfood.org.uk

Hindgut FermentersColon Fermenters

Horse, Elephant, Rhino

ADM Alliance Nutrition®

http://www.mi-feed.com.au/past_nutrition.php?page=Mar2006

Hindgut Fermenters

Location Substrate Digestive Agent End Product

Stomach Pepsin Amino Acids

Small Intestine

Carbohydrates

Proteins Trypsin, Carboxypeptidase

Lipase

Glucose, Maltose

MAG’s, FA’s

Large IntestineMicrobes VFA’s

Mineral & Water absorption

Origins of Simple Stomach Animals

(Van Soest, 1994)

Gastrointestinal Tract (GIT) Functions

Diet

MouthEsophagus

StomachSmall Intestine

Large IntestineAnus

Foregut FermenterKangaroo

(Van Soest, 1994)

Foregut FermenterRuminants

Sheep, cattle, goats, elk, white-tailed deer

(Van Soest, 1994) http://www.youtube.com/watch?v=cWg1u1bUKNc

Feed Prehension Mastication & deglutition (swallowing) & salivation

Anterior rumen or reticulum

Mixed in Rumen, Fermented

Small Particles

Abomasum Small Intestine Feces

No, Small ParticlesYes

No, Larger particles than

rumination

Nursing

RumenPurpose

Major site of anaerobic fermentation

Mixes rumen contents

Mucosa

Filiform and foliate

Increase surface area

Layers in Rumen

cm scale

454 g

Marker

1362 g

MinutesC

entim

eter

s

10203040

1 2 3

Gas

(Van Soest, 1994)

ReticulumPurpose

Distributes feed tot he omasum

Origin of primary rumen contractions

Some VFA absorption

Mucosa

increase surface area

Traps small particles

Omasum

Purpose

Pump food to the abomasum

Some VFA and H2O absorption

Mucosa

Arranged on muscular laminae

AbomasumPurpose

Produces HCl

Secretes proteolytic enzymes

pH 2-3.5 to prepare food for lower GIT

Mucosa

Arranged in folds

RuminantsLocation Substrate Digestive Agent End Product

Reticulo-rumenProtein

CarbohydratesLipids

Microbial ProteinVFA’s

TAG, FFA’s

Omasum Water & Mineral absorption

Abomasum Pepsin Amino Acids

Small Intestine

Carbohydrates

Proteins

Lipids

Amylase, Glucosidase

Trypsin, Carboxypeptidase

Amino Acids

MAG’s, FFA’s

Large IntestineCarbohydrate Microbes

Approximate relative capacity of ruminant stomach compartments

(Acker & Cunningham, 1991)

Compartment At birth At 4 months At maturity

Rumen 25% 75% 80%

Reticulum 5% 5% 5%

Omasum 10% 9% 7%

Abomasum 60% 11% 8%

Total 100% 100% 100%

SummaryThe architecture of the GIT and the agents of digestion are of utmost importance to determine digestive function

Ruminants and hind-gut fermentors have well developed fermentation sites

Hind-gut fermentors have greater rate of passage and can survive on lower quality food

Ruminants can eat lower quality forage but must retain food for a longer period of time