1499

Comparison

of

Digestive

Function

Among

Rabbits,

Guinea-Pigs,

Rats

and

Hamsters.

I.

Performance,

Digestibility

and

Rate

of

Digesta

Passage

Peter

Wen-Shyg

Chiou

*

,

Bi

Yu

and

Chung-Yi

Kuo

*

Address

reprint

request

to

Peter

Wen-Shyg

Chiou.

Tel:

+886-4

-

287-0613,

Fax:

+886-4-286-0265,

E-mail:

wschiou@

dragon.nchu.edu.tw.

Received

Januaiy

26,

2000;

Accepted

June

27,

2000

Department

of

Animal

Science,

National

Chung-Hsing

University,

250

Kuo-Kuang

Road,

Taichung,

Taiwan,

ROC

ABSTRACT

'

This

trial

was

to

compare

the

digestive

function

of

laboratory

animals,

which

included

omnivores

(rats)

and

herbivores

(rabbits,

guinea

pigs

and

hamsters).

Ten

weanling

rats,

rabbits,

guinea

pigs

and

hamster

were

randomly

allocated

in

individual

metabolic

cages

for

a

performance

and

a

digestibility

trial.

Results

showed

that

guinea

pigs

were

significantly

best

in

digestion

of

dietary

crude

protein

and

fiber.

Rabbits,

however,

had

the

poorest

nutrient

digestion

among

the

herbivores.

Crude

fiber

digested

significantly

less

by

rats

than

by

the

herbivores

(p<0.05).

The

digesta

retention

in

the

GI

■

tract

was

longest

in

rabbits

followed

by

guinea

pigs,

rats

and

hamsters.

The

relative

length

of

the

large

intestine

was

significantly

shorter

in

rats

as

compared

to

guinea

pigs

or

hamsters.

Both

the

weight

and

length

ratio

of

the

caecum

or

colon-rectum

to

the

large

intestine

reflected

the

major

site

for

fermentation

that

was

the

caecum

in

rabbits

and

the

colon-rectum

in

guinea

pigs.

10%

of

crude

fiber

diet

did

not

result

in

damaged

mucosa

in

any

of

the

experimental

animals

in

this

trial.

(Asian-Aus.

J.

Anim,

Sci.

2000.

Vol.

13,

No.

11

:

1499-1507)

Key

Words

:

Herbivores,

Laboratory

Animals,

Performance,

Digestibility,

Rate

of

Digesta

Passage,

Crude

Fiber

INTRODUCTION

The

animals

that

are

most

extensively

use

in

the

laboratory

are

rabbits,

guinea

pigs,

rats

and

hamsters.

These

animals

are

all

hindgut

fermenters

and

herbivores,

except

rats

which

are

omnivores.

Growing

rabbits

(NRC,

1977)

and

guinea

pigs

(NRC,

1995)

require

10

—

12%

and

15%

crude

fiber,

respectively,

in

their

diet.

Although

the

specific

amount

of

crude

fiber

required

by

rats

and

hamsters

has

not

yet

been

determined,

the

crude

fiber

in

their

diets

has

generally

been

emphasized

due

to

its

significance

in

digestive

function.

Research

data

have

suggested

that

a

10%

dietary

fiber

or

cell

wall

is

required

in

the

diet

for

rats

(Nyman

and

Asp,

1985;

Pond

et

al.,

1989).

The

hindgut

which

includes

the

caecum,

colon

and

rectum

is

the

major

site

of

fermentation

in

these

herbivore

non-ruminants,

where

volatile

fatty

acids

(VFA),

end

products

of

fermentation,

are

absorbed

by

the

host

animal

as

an.

energy

source

(Parker

and

McMillan,

1976;

Zhao

et

al.,

1995).

Cecotomy

of

these

animals

significantly

depressed

rat

and

hamster

ability

to

digest

dietary

dry

matter

and

crude

fiber

(Sakaguchi

et

al.,

1981;

Williams

and

Senior,

1982),

but

showed

no

significant

impact

in

rabbits

(Gioffre

et

al.,

1980).

Rabbits

are

not

good

digesters

of

fiber.

They

digest

crude

fiber

less

well

as

compared

to

guinea

pigs,

but

can

digest

cellulose

and

hemicellulose

as

well

as

rats

(Fonnesbeck

et

al.,

1974).

Rabbits,

however,

cannot

survive

on

a

low

fiber

diet

(6%

of

crude

fiber).

This

is

also

true

for

rats

and

hamsters

on

a

crude

fiber

free

diet.

Feeding

rats

and

hamsters

on

this

kind

of

diet

causes

high

mortality

or

depressed..

.

growth

(Cheeke

and

Patton,

1980).

On

the

other

hand,

dietary

crude

fiber

is

beneficial

to

guinea

pigs

in

depressing

the

growth

of

pathogenic

bacteria,

；

；

Bacteroides

ovatus,

in

the

intestine,

hence

improving

the

growth

of

guinea

pigs

(Johanning

et

al.,

1984).

Increased

levels

of

crude

fiber

in

the

diet

generally

decrease

feed

conversion

efficiency

in

rabbits

and

rats.

This

may

be

attributed

to

the

changes

in

the

GI

tract

that

enhance

the

digestive

function

in

these

animals.

In

the

rats

an

increase

in

the

level

of

dietary

fiber

,

significantly

increases

the

intestinal

weight

and

length

:

of

various

sections

of

the

GI,

but

decreases

nitrogen

retention

which

results

in

decreased

growth

(Zhao

et

aL,

1995).

For

non-ruminant

herbivores,

dietary

fiber

is

therefore,

significant

as

a

source

of

bulk

in

the

digestive

physiology,

not

as

a

source

of

nutrients.

The

biological

classifications

of

these

laboratory

,

animals

are

closely

related.

Rabbits

belong

to

the

：

order

of

Lagomorpha,

Rats

and

hamsters

belong

to

order

of

Rodentia-

and

guinea

pigs

are

hystricomorph,

r:

Some

specific

digestive

functions

in

the

various

；

sections

of

the

GI

tract

should

be

similar

among

these

;

animals.

Research

information

is

limited

on

the

comparative

effects

of

crude

fiber

on

their

digestion.

This

trial

is

therefore

aimed

at

study

of

the

differences

in

digestive

function

in

these

laboratory

animals

and

their

utilization

of

crude

fiber.

MATERIALS

AND

METHODS

Animal

and

diets

Ten

four-week

old

weanlings

of

each

animal

species

with

equal

numbers

of

each

sex

and

a

mean

live-weight

of

1,021

g

for

the

California

rabbit,

175

g

for

the

Hartley

guinea

pig,

165

g

for

the

'

Wistar

rat