Lab Animal & Small Mammal

Husbandry

Rats

CHAPTER

Rats

12

Rattus norvegicus

• Rat – Rodent, quiet, intelligent, easily trained

Introduction to Rats

• Belong to rodents order of gnawing mammals (Rodentia)– With mice compose subfamily Murinae– True rats form genus Rattus

(78 to 570 species)

• Two domesticated rat species– Black– Brown

History of Black and Brown Rats

• Black rat– May have come from Southern Asia– Well established in Europe during 1200s– Reached North America during 1500s

• Brown rat– Came from Eastern Asia and Northern

China– Went to Europe and North America in

1500s– Now well established in United States

Common Background of Rats

• Have spread across the world– Can adapt to many different habitats, environments, and foods– Reproduce rapidly

• Cause tremendous damage– Destroy eggs, fruits, stored grain, and vegetables– Attack humans and other animals– Damage buildings and cause fires– Carry diseases

• Play important role in research– Used extensively in drug development– Act as subjects in disease, aging, behavioral, and other

studies

Black Color Group of Rats

• From 7 to 8 inches long (head and body)– Tail longer than head and body– Ears about half as long as head

• Weigh 4 to 12 ounces

• Usually black or dark gray with brown or gray-white underside

• Excellent climbers and jumpers

Brown Color Group of Rats

• From 7 to 10 inches long (head and body)– Tail shorter than head and body– Overall thicker, more robust than black rats

• Weighs 7 to 17 ounces• Dark to gray-brown back with lighter brown

or gray underside• Not climbers, prefer tunnels, burrows,

sewers, and basements

Varied Color Group of Rats

• Albino (white laboratory rat)

• Cream, fawn, or light gray

• Hooded

• Capped

Breeding• Life span 2 to 3 years

• Puberty at 50 to 60 days• Continuously polyestrous (minor seasonal variation)

• Gestation 21 – 24 days– Pregnancy determination @ 14d– Pseudopregnancy may last up to 14d

• Litter size 7 to 11– Don’t disturb for 3-4 days after delivery– Young born pink, naked, blind, deaf – Young have hair by 1 week old

• Wean at ~21 days

Characteristics of Common Rats

• Agile climbers• Excellent swimmers• Highly curious• Clean and odor free• Seldom prone to biting• Imposing when upset or angry• Gregarious• Primarily nocturnal

Anatomy

• Absence of gallbladder

• Open rooted incisors

• Extensive mammary tissue

• Have an os penis

• Olfactory oriented• Harderian gland

behind eyeball secrets porphyrin

• Average weight 350g

• Altricial

Desired Qualities of Rat Cages• Larger than 12” x 24” x 12” ESCAPE PROOF• Nest box & 2-4x more space if breeding• 65-80 F temperature, 40-70% humidity• Wire mesh or glass sides• Solid bottom or pull-out tray• Outside-hanging water bottle (spout inside)• Glass or ceramic feed bowls• Exercise equipment (ladders, ropes, wheels)• Wood shavings or other appropriate bedding

– Change 1-2x per week or more if moist/odor

• Nesting materials

Methods of Feeding Rats

• Commercial pellets easiest option

• Supplements – NOT NECESSARY– Dry dog food, crackers, cereal, fruits or

vegetables (less than 5-10% of diet)– Vitamins and minerals

• Daily water– One ounce per rat– Closed dish, sipper bottle

Behavior

• Long Evans more aggressive than albinos

• Communal

• Young are communally raised

• Burrowers

• Nocturnal

Methods of Handling Rats

• Young rats– Grasp around body, just behind front legs– By tail, grasp at base close to body

• Older rats– Use talking as relaxation technique– When not tame: Go slowly, get attention, grasp by

base of tail, and lift– For further restraint: Place second hand around

body just behind front legs and restrict head movement with thumb and forefinger

Rat Diseases and Ailments• Neoplasia

• Respiratory disease– Commonly caused by Mycoplasma pulmonis– Treatment with antibiotics– Controlled with good sanitation and ventilation

• External parasites (lice and mites)– Cause hair loss, itching, more

serious symptoms– Controlled with shampoo containing pyrethrin

Mycoplasmosis (respiratory disease)

• Signs: Sneezing, nasal discharge, eye discharge, labored breathing

Treatment: Long term antibiotics

Prevention: Clean environment, good ventilation

Red Tears (sialodacryoadenitis)

Signs: Because rodents have porphyrins (pigment) in their tears, any discharge will be red.

Causes: bacterial infection or stress

Treatment: Topical eye ointment

Mammary Neoplasia Frequently develop tumors. Mammary tissue covers most of the body, so lumps can appear anywhere.

Grow quite large , are uncomfortable and may ulcerate and become infected.

Surgical removal is necessary

Copyright © 2010 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23

Rats and MiceRats and Mice

Territorial animalsTerritorial animals Usually aggressive, and will biteUsually aggressive, and will bite Require small amounts of food and waterRequire small amounts of food and water Escape proneEscape prone Common clinical conditionsCommon clinical conditions

Ectoparasites, neoplasia, and traumaEctoparasites, neoplasia, and trauma

Mice

CHAPTER

Mice

13

Mus musculus

• Mice Rodent – world wide, many varieties

History of Common House Mice

• Believed to have originated in Asia• Gained place in history

– Egyptians and Romans used phrases like “It’s raining mice” or “Mice are made of raindrops”

– Cretans worshiped mice over 4,000 years ago

– Mice were used as medicines in ancient Rome and during Middle Ages

– Japanese bred white/colored mice 3,000 years ago

• Today house mice are widely used in medical and biological research

Basic Color Groups of Mice

• Self or single colors

• Tans, any recognized colors with tan belly

• Piebald or pied marked

• Satins of any color or markings but with satinized coat

• Any other variety

Breeding

• Life span 2 – 3 years

• Puberty at 28 to 40 days

• Gestation period 21 days

• Litter size 6 – 12

• Weaned at 21 days

Mouse Reproduction

• Sexual maturity– Females at 4 weeks– Males at 5 weeks

• Gestation period normally ~21 days• Litters range from 5 to 10 to 1 to 20

– Young born helpless, hairless, and blind weighing ~1 to 2 grams and measuring ~1/2” long

– Touch no young for at least a week– Separate by sex at about 3 weeks to prevent

unwanted matings

Characteristics of House Mice

• About 2½ to 3½” long (without tail)• Weighs ½ to 1 ounce• Small head with long, narrow snout• Gray-brown back, light to white underside• Large, round, black eyes• Large ears and well-developed hearing• Highly developed sense of smell• Primarily nocturnal• Gregarious

Anatomy

• Porphyrin Glad behind eyeball

• Small size 25-40 grams

• Open rooted incisors

• Males have larger spleen than females

• Extensive mammary tissue

• Fecundity – one pair plus one year equals one million

• Altricial

Desired Qualities of Mice Cages

• For mouse pair at least 72 square inches of floor space and 8 inches of height

• Plastic bottom and closely spaced bars• Cover or lid• Wood, nondusty shavings or other

appropriate bedding• Vacuum-type water bottle

Nutrition/Housing

• Metal or plastic cages with wire mesh

• Water bottles

• Bedding & nesting materials

• Commercial diets

• No supplements

Common Foods for Mice

• Grains and seeds as main foods– Commercial pellets– Grain/seed mixture

• Ration of corn, oats, and wheat with small amounts of millet, barley, and buckwheat– Feed sunflower seeds sparingly– Give small amounts of oily seeds– Add greens and vegetables

• Fresh hay as supplement

Behavior

• Timid

• Territorial

• Escape prone

• Social order poorly understood

• Males cannot be housed together after sexual maturity MOB Syndrome

• Will bite when handled roughly

Clan/Colony Structure of House Mice

• Ruled by lead or head buck– Only lead buck mates, all other males subordinate– Subordinates challenge buck through aggression– Defeated buck moves to bottom of social structure

• Females together raise, warm, nurse/feed young

• Structure provides protection and makes finding and storing large quantities of food easier– Members leave urine marks while searching– Marks fend off members of other colonies

Methods of Handling Mice

• Two ways to lift– Grasp by base of tail– Scoop up in cup

• Allow adjustment period when first home• Offer treats from fingertips and then palm• When tamed, stroke head and ears

Mouse Diseases and Ailments

• Respiratory diseases

• Infectious diseases

• Mites

• Pinworms

• Protozoans

Common Diseases

• Mammary Neoplasia – same as rats

• Mycoplasmosis – same as rats

• Viral Diseases: more a problem is laboratory colonies than in pet mice

• Antibiotic toxicities: Procaine and streptomycin are fatal to mice