Small Animal Science Sample Lesson

MAIN IDEA: What is the most common type of rat and what are the basic housing and equipment requirements for rats?

CLASSIFICATION

Many species of rats exist in the wild, but only the black rat (Rattus rattus) and the brown rat (Rattus norvegicus) have been domesticated for use in research and as pets. The rat is a mammal of the order Rodentia and the family Muridae. Norway rats or laboratory rats (Rattus norvegicus) were the first animal where the primary reason for domestication was for use in scientific endeavors.

White albino laboratory rats are descendents of the brown rat produced through mutations and selective breeding. They have several unique biological characteristics. The acute hearing of rats makes them sensitive to ultrasounds and high pitched sounds. The vision of rats is very poor -- they are unable to detect color and are blind to long-wave (red) light. The hairless tail of the rat is the principal organ for heat exchange.

Adult males can weigh 11 to 28 ounces (300 to 800 grams) and adult females can weigh 9 to 14 ounces (250 to 400 grams). Rats become sexually mature at 65 to 110 days old. They live 2 to 3.5 years.

GROUPS/BREEDS

Rats are not grouped into breeds but they are grouped by their microbial colonization, genetics, markings and coat colors. Also, a miscellaneous group contains some unique rats.

Scientific groupings:

For scientific purposes, rats are grouped by their microbial colonization:

1. Specific Pathogen Free (SPF) rats are free from known bacterial, viral and parasitic rat pathogens, as opposed to "conventional" rats, which are not known to be free of pathogens.
2. Axenic rats are free from organisms.
3. Gnotobiotic rats have a defined microbial flora.

Also, for scientific research, rats are categorized genetically. Common genetic categories include:

• Random-bred rats which are managed to maintain genetic diversity by mating unrelated rats;
• Inbred rats which are managed to maintain genetic homozygosity by breeding siblings;
• F1 hybrid rats which are produced by crossing two inbred strains for one generation; and
• Mutant rats

Inbred, outbred, hybrid or mutant rats are available from many commercial sources. Typically, commercially available rats for research are shipped and arrive within a week. Animals will recover from the stress of shipping within 48 hours.

Markings and coat colors:

Mutations and selective breeding of black and brown rats produce a variety of coat markings such as:

• Caped
• Dalmatian
• Hooded
• Masked
• Variegated

Also, through mutations and selective breeding, the black and brown rat can be found in many coat colors including the following:

• Agouti
• BEW - Black Eyed White
• Black
• Blue Seal Point Siamese
• Blue-Agouti
• Buff
• Champagne
• Chinchilla
• Chocolate
• Cinnamon Pearl
• Cinnamon
• Coffee
• Dove
• Himalayan
• Lilac
• Lynx
• Mink
• Mocha
• Pearl
• PEW - Pink Eyed White (Albino)
• Siamese
• Silver Black
• Silver Fawn
• Silver Mink
• Silver Lilac
• Topaz

Rat coat types can be standard, rex (wavy or curly fur), hairless (nude) or satin.

Miscellaneous:

Dumbo rats have broad heads and large, round, low-set ears. Manx (tailless rats) are slightly smaller than their tailed siblings and either have a "stub tail" or totally lack a tail. Dwarf rats are anywhere from two-thirds to one-half the size of normal rats. Dwarf rats can be comparable to the size of a gerbil.

HOUSING/EQUIPMENT

Most laboratory rats are housed in shoebox cages made of polypropylene (opaque) or polycarbonate material (clear) with a wire bar lid used to hold the water bottle and feed. Bedding is placed directly into the shoebox cage to absorb urine and allow the animal to burrow. Bedding material should be absorbent and free of any substances that might harm the animals or alter research data. Cedar and pine products should be avoided, since they can affect liver enzymes which may in turn affect immunologic or other physiologic parameters. This type of cage will hold one to three adult rats depending on the size of the cage. According to the "Guide for the Care and Use of Laboratory Animals," different sizes of rats require the floor space indicated in Table 1.

    Table 1. Floor Space Requirements of Rats

    Size (grams)      Square Inches
    less than 100          17
    up to 200              23
    up to 300              29
    up to 400              40
    up to 500              60
    more than 500          70+

Table 1 is only a guide. Actual space required by rats needs to be based on their health, reproductive stage, growth, behavior and activity.

Some rats are housed on wire mesh bottom cages to allow feces and urine to drop through for collection purposes, or to prevent contact with bedding. This type of housing is not preferred and is used only when required by experimental design. Suspended cages are occasionally provided with automatic watering.

For research purposes some rats are housed to prevent them from getting any rodent diseases. These animals are housed in sterilized cages and are provided sterile food and water. Access to this housing area is limited to prevent the inadvertent transmission of rodent pathogens by personnel.

During research, cage cards are used to identify the strain of rat, sex, number, principal investigator and research protocol. Individual rats can be temporarily identified by pen marks on the tail, hair clipping, or dyeing the fur. Pen marks will only last one to two days, but hair clipping may last up to 14 days. Tail tattooing is a permanent identification method.

For the owner of pet rats, the cage can be the same type as used for gerbils and hamsters. Cages can be made of all wire mesh, or wood and wire mesh. Wood is not ideal since rats need to gnaw and will probably gnaw the wood. Wood also soaks up urine, making it difficult to clean. Glass aquariums with escape-proof lids also work as cages for rats. The size of the cage used should be based on the guidelines in Table 2.

    Table 2. Cage Size Recommendations

    Number of Rats            Dimensions (inches)
    Pair and litter           10 X 16 X 10
    2 females + male          12 X 24 X 10
    3 to 4 females + male     12 X 30 X 10

Wood shavings or chips are good for bedding material and for nest building by pregnant females. Paper towels, paper napkins or toilet paper can also be used.

Water bottles need to be hung on the outside of the cage or protected from gnawing if they are hung on the inside of the cage. Feed bowls should be made of glass or ceramic since this is easy to clean and gnaw-proof.

If the cage is large enough, active rats enjoy exercising on ropes, ladders and wheels.

EXERCISE:

1. Some people have a rat as a pet, but the real value of rats is in their use in medical, biological and psychological research. Find one research project where rats are being used and report your findings. Determine the purpose of the research, where it is being conducted and if the research is medical, biological or psychological. A good place to start looking is the Web site for the American Association For Laboratory Animal Science listed under Internet Resources.

INTERNET RESOURCES:

** American Association For Laboratory Animal Science
http://www.aalas.org/

** American Fancy Rat and Mouse Association
http://www.afrma.org/rminfo1.htm

TEST:

1. Rats belong to the __________ family.
A. Canidae
B. Muridae
C. Hylidae
D. None of the above

2. Rats have excellent eyesight. TRUE or FALSE?

3. List the four ways rats are grouped.
A.
B.
C.
D.

4. White rats have tails that are:
A. Hairless
B. Bushy
C. Straight
D. No tail

5. Axenic rats are free from __________ .

6. Rat coat types are standard, __________ , hairless, or __________ .

7. Dwarf rats are comparable to the size of __________ .

8. Name three ways to mark or identify rats for research purposes.
A.
B.
C.

9. Water bottles and feed dishes do not need to be gnaw-proof. TRUE or FALSE?

10. Rats enjoy:
A. Ropes
B. Wheels
C. Ladder
D. All of the above

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END OF STUDENT SECTION

TEACHER'S GUIDE

SA117 Rat Groupings, Housing and Equipment

OBJECTIVE: The student will be able to describe the types of rats and suggest proper rat housing and equipment.

PREPARATION: Take the following steps to prepare for this lesson:
1. Read and review this lesson material
2. Visit a pet store and become familiar with rats and their supplies.
3. Visit the American Fancy Rat and Mouse Association Web site for information and other links.
4. Decide which of the Extension activities will be used and then obtain the necessary supplies or make the necessary contacts.

INTERNET RESOURCES:

** American Association For Laboratory Animal Science
http://www.aalas.org/

** American Fancy Rat and Mouse Association
http://www.afrma.org/rminfo1.htm

IMPORTANT TERMS: domesticated, albino, microbial colonization, SPF, axenic, gnotobiotic, mutant, homozygosity, flora, inbred, outbred, hybrid, rex, manx, dwarf, pathogens, tattooing.

EXTENSION IDEAS:

1. Rats and their equipment are quite inexpensive. Purchase some rats and become familiar with their housing and equipment needs, their care and their behavior.

2. Have a veterinarian or a researcher discuss the importance of using rats for research.

EXERCISE ANSWER:

1. Answers will vary but rats have been used for the development of drugs, the study of diseases, nutrition and aging. Also, they have been the subject of many behavioral studies. Some of the current uses of rats include the study of AIDS, cancers, immunology and genetic engineering.

TEST KEY:

1. Rats belong to the __________ family.
A. Canidae
B. Muridae
C. Hylidae
D. None of the above

Correct answer: B. Muridae

2. Rats have excellent eyesight. TRUE or FALSE?

FALSE. Rats have very poor vision. They are unable to detect color and are blind to long-wave (red) light.

3. List the four ways rats are grouped.
A. Microbial colonization
B. Genetics
C. Markings D. Coat colors

4. White rats have tails that are:
A. Hairless
B. Bushy
C. Straight
D. No tail

Correct answer: A. Hairless

5. Axenic rats are free from organisms.

6. Rat coat types are standard, rex, hairless, or satin.

7. Dwarf rats are comparable to the size of gerbils.

8. Name three ways to mark or identify rats for research purposes.

Any three of the following are correct: cage cards, pen marks on hair, hair clipping, dyeing, tail tattooing.

9. Water bottles and feed dishes do not need to be gnaw-proof. TRUE or FALSE?

FALSE. Rats need to gnaw and will destroy items that are not gnaw-proof.

10. Rats enjoy:
A. Ropes
B. Wheels
C. Ladder
D. All of the above

Correct answer: D. All of the above

CROSSWORD PUZZLE ANSWERS:

Across: 1. Rex, 3. Dwarf, 5. Dumbo, 9. Inbred, 11. Gnotobiotic, 13. Pine, 14. BEW.
Down: 1. Random, 2. SPF, 4. Albino, 6. Manx, 7. Axenic, 8. Black, 10. Brown, 12. Nude, 13. PEW.
------------------------------------------------------------------------------
Copyright © 1999 Stewart-Peterson, Inc. All Rights Reserved. RF/nc,tl 990390
STEWART-PETERSON and AGEDNET.COM are registered trademarks of Stewart-Peterson, Inc.

END TEACHER'S GUIDE

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