COmmon Lab Animals

1. Couse number AGB 610
Course Title: Laboratory Animal Breeding
Common Laboratory animal and Breeding Colonies
Instructor: Dr Shanker Dayal
Univ. Professor, AGB

2. Laboratory animals Species Used In Research
Mice
Scientific Name: Mus musculus
small and prolific and most economical amongst lab animal
easy to handle and have a very convenient tail which can
be used for restraint and collection of blood
most widely used laboratory species accounting for over
50% of animal use
widely used by immunologists, oncologists and geneticists
wide range of genetically defined inbred stains and
mutants are available

3. Several mutants strains have been developed, some of which
are of great value in research. eg. animals homozygous for the
athymic nude mutation have no cell-mediated immune
responses and can be used to grow tissue and tumour
xenografts of human origin.
Other popular mutants strains include obese (ob), diabetic (db),
dominant hemirnelia (Dh, which is also asplenic) and lymph
proliferation (lpr) which causes autoimmune disease.
More than 350 different inbred strains of mice are available,
though most research is conducted on about 10-12 of the most
common strains.
more popular mouse strains are BALB/c, C57BL/6, C57BL/10,
CBA/Ca, C3H/He, DBA/2, SJL and SWR.

4. A large number of congenic mouse strains, produced by
backcrossing a gene to an inbred background (the inbred
partner strain) have also been developed. Such strains are
essential for work involving the study of immune responses
to parasites, viruses and bacteria, as well as chemical
antigens.
Congenic mice An inbred strain of mouse that contains a
small genetic material (preferably single gene) from
another strain but otherwise identical to the original
inbred strain.
Mice are not suitable for experiment requiring
experimental surgery due to its small size

5. Rat
Scientific Name Rattus norvegicus
Rats are prolific and are well suited to laboratory
conditions.
Rats weight about ten times as much as mice, so they are
particularly suitable for research which requires larger
quantities of tissue, or surgical techniques which are
difficult in an animal as small as the mouse
Rate are generally preferred over mice by toxicologists and
pharmacologists because of their convenient size, and
because they do not have so many virally-induced tumours
as mice.

6. Syrian Hamster
Scientific Name Mesocricetus auratus
intermediate in size between mice and rats
reasonably prolific, and do well in cages which are suitable
for the rat, so the cost of breeding and maintaining them is
approximately the same as for the rat
they are the only common laboratory species which can be
induced to hibernate have a cheek pouch which is an
immunologically privileged site and can be used to grow
some tumour xenografts and the hamster egg can be used
to assess the fertilizing capability of human semen.

7. Guinea-pigs
Scientific Name Cavia porcellus
They have a long gestation period (about 65 days compared with 21 days in
the rat), and a small litter size (about 4 young compared with 10-12 in the rat),
but the young are quite mature at birth with a good coat of hair and open
eyes.
They require dietary source of vitamin C.
There are a few established inbred strains of guinea-pigs such as strains 2 and
13.
most commonly used as a source of complement (i. e. serum) and other
biological fluids and tissues in immunological assays, and as a source of tissue
(e. g. vas deferens or gut) in pharmacological studies.

8. Rabbits
Scientific name Oryctolagus cuniculus
Prolific
ovulation induced by mating
Short gestation period (31-33 days)
widely used in reproductive studies, particularly in
teratogenicity investigations as it is the only common
species producing malformations on treatment with
thalidomide.
Teratogenicity Capability of producing foetal malformation
widely used for the production of antisera as they are a
convenient size

9. used routinely for testing pharmaceutical preparations for the
presence of pyrogenes.
Other species
Fish are widely used for toxicological studies of e. g. agro-
chemicals and industrial waste waters.
Amphibian are used for studying development, physiology, and
for teaching
Dogs are widely used in toxicology and for experimental
surgery
Cats are commonly used by pharmacologists and physiologists
to study short-term drug and hormone responses
Many species of primates are used in a wide variety of studies
which require animals which resemble man as closely as
possible.

10. Animal Temperature (oC) Humidity (%)
Mouse
Rat
Hamster (Syrian)
Gerbil (Mongolian)
Guinea Pig
Rabbit
Cat
Dog
Pig
Chicken
Nonhuman Primate:
-New World & Prosimians
(Howler monkey)
-Old World (Baboon,
Macaques)
18-26
18-26
18-26
20-22
17-25
16-21
18-29
16-27
22-26
18-26
-
-
40-70
40-70
40-70
30-50
40-70
40-60
30-70
30-70
45-70
60-65
45-60
Recommended Room Temperatures and Relative Humidity for Adult Laboratory Animals

11. Breeding data for some common laboratory species
Character Mouse Hamster Rat Guinea-pig Rabbit
Typical adult weight (g) 25-30 150 250-400 500-800 1000-7000
Average longevity (years) 1-2 2-3 2-3 4-8 5-6
Age at puberty (days) 35 45-60 45-75 45-75 150-210
Usual breeding age (days) 50 56 80 80 150-210
Mating system M,C D,M M,H C D
Length of oestrus cycle (d) 4-5 4 4-5 14-16 n.a.
Ovulation S S S S I
Gestation period (days) 20 16 21-23 65-72 32-32
Average litter size 6-10 4-8 6-12 3-4 6-8
Weight at birth (g) 1-2 1-2 5-6 85-90 -100
Weight at weaning (g) 10-12 35-40 -250 -1000
Age at weaning (days) 19-21 21 21 14-21 50
Productivity (young per 25-75 25-50 25-100 12-18 15-20
Breeding unit per year*)
M – Monogamous pair C – Colony D- Hand mating H- Harem mating S- Spontaneous I- Induced

12. Mice Breeding colony
Life span 2.5 years; however,
reproductive life span 7-8 months.
sexual maturity (males and females) at 4-7 weeks of age.
Younger mice generally produce smaller litters and therefore are not typically
mated until they reach 6-8 weeks, of age.
Mice that have been housed alone or in same-sex pairs will usually not breed
successfully if they are older than 6-8 months.
Estrous cycle 4-5 days in length.
Mice cycle continuously throughout the year (non-seasonal breeders). Female
mice are only receptive to males when they are in estrus.
Mating typically occurs at night (Light off)
Ovulation occurs 8-10 hrs after the onset of estrous.
If fertilization occurs, fetuses can be palpated by day 14.

13. Gestation in mice is typically 19-21 days (strain dependent).
Parturition may last 1-3 hours and frequently occurs at night.
Females will go into estrus within 24 hours of parturition and are sexually
receptive during this time.
Litter size varies among strains, but averages 4-12 pups. Inbred mice tend to
have smaller litters than outbred mice.
Mice are typically weaned at 21-28 days pr at 10 gm body weight
Factor effecting reproduction
Strain
Age
Environment
Diet – High Fat 11% vs 4% in some strain
Health
Pheromones

14. Lee-Boot Effect: Housing female mice in close density in isolation from male mice will
result in the suppression of estrus This phenomenon in combination with the
Whitten effect, is used to synchronize estrus in female
Whitten Effect: Male mouse urine contains a pheromone that induces estrus in
previously suppressed females within three days.
Bruce effect (Pregnancy block):This is the phenomenon by which female mice
terminate their pregnancies during the preimplantation period, following exposure to
the scent of an unfamiliar male. During the first 5 days of pregnancy, females should
not be exposed to foreign males or their soiled bedding

15. Rat Breeding colony
Generally, male laboratory rats will reach sexual maturity at approximately 10-12
weeks of age, although females may have their first estrus as early as 8-9 weeks of
age.
The reproductive lifespan of rats is on average between 12 and 15 months.
The duration of the estrous cycle is 4–5 days. The cycle is divided into four
characteristic phases: proestrus, estrus, metestrus and diestrus. The stage of the
estrous cycle can be determined by vaginal cytology.
Rats are polyestrous and breed year round
ovulation is spontaneous.
Mating is usually nocturnal.
Gestation period: 21-23 days
Weaning age: 21-23 days
Pregnancy may be confirmed by gentle abdominal palpation after gestation day
A fertile postpartum estrus occurs within 48 hours of giving birth and mating at that
time are better than 50% successful.
Failure to conceive at that time will delay breeding until two to four days after the
litter is weaned.

16. Breeding cages should be observed daily for new born, weaning, separating of
females, and a check of the animals health and general condition.
The maintenance of good breeding records is essential.
Breed the female is at least 90 days old and approximately 200-275g,
depending on strain.
Young males should not be used until at least three months of age or weigh
275-350g.
Breeding stock is replaced
Before their reproductive performance begins to decline. Breeding success
decreases if the rats are older than 9 months old.
If no litters have been born in 2 months and female is not pregnant (unless
strain is known to have low fertility)
If several litters have been born but no pups have been weaned.
If a significant decrease in litter size is noted
Do not replace all breeding animals at the same time. It is best to have
breeding animals of various ages in the colony.