Chapter Seventeen

1
Chapter Seventeen

• Rats

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3
Rats

• Developed from wild brown Norway rat.
• Model for naturally occurring disease studies
  such as diabetes hypertension.
• Wistar albino (WI) - wide head, long ears, tail
  shorter
• than body
• Sprague-Dawley (SD) albino faster growing than
  WI
• longer, narrower, head tail long as body
• Long-Evans (LE) - smaller than WI or SD, white
  fur w/
• black patches, head is usually black,
  sometimes known as the hooded rat
• F344 Lewis inbred rat strain commonly used

4
Handling and Restraint

• Pick up by base of tail.
• One hand is placed over animals back, w/ thumb
  forefinger pressing forelegs toward head.
• Commercial plastic restraint devices useful for
  some procedures.
• Rats more relaxed the more they are handled.

• For control, tail or hindquarters may be
  restrained w/ other hand.
• Must not be grasped so tightly around thorax that
  breathing is restricted.
• Can also be wrapped in towel.

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Physiological Data

• Body temp 35.937.5C(96.699.5F)
• Heart rate 250 - 600 / min.
• Respiration rate 66-144 / min.
• Weight adult male 300500 grams adult female
  200400 grams newborn 5 grams
• Water consumption 24-60 ml / day or 10-12
  ml/100 g body weight daily
• Food consumption 15-30 g / day or 5-6 g / 100 gm
  body weight daily
•  Feces firm, dark brown, elongated mass.
•  Urine urine should be clear yellow.
•  Life span 2.5-3.5 years

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(Images) Size and Age of Rats
4 weeks old and 6 months old
2 years old gt500 grams porphyrin stained hair
coat
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Sexing and Breeding

• Anogenital distance is about 2x gt in male as in
  female.
• In adult rats, testes protrude from beneath
  tail.
• Females are polyestrous have a postpartum
  estrus.
• Receptive to male within 24 hours of parturition
• Born pink-skinned, hairless, helpless.
• Other breeding data
• sexual maturity 65110 days
• estrous cycle 45 days
• gestation 2022 days
• litter size 711
• Cannibalism Usually female rat does not
  cannibalize.
• Weaning 21 days

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(Images) Sexing Rats
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Behavior

• Sitting hunched over is an early sign of poor
  health.
• Keep groomed clean if healthy.
• Nocturnal
• Group housed males rarely fight.
• Female rats usually docile in group housing.
• Tears saliva contain porphyrin.
• Seen around eyes end of nose, noticeable on
  white fur.
• Older animals, all of fur appear reddish in color
  due to licking itself while grooming.
• Excessive accumulation of porphyrin around eyes,
  nose or on front legs can be a sign of illness.

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Husbandry

• Shoebox suspended wire-bottom
• Single group housing
• Can knock off unsecured cage lids.
• Change shoebox cages 1 or 2x/wk.
• Sanitize shelving racks at least 1x / 2 wks.
• Clean drop pans at least 2x / wk.
• Front (incisor) teeth grow continuously.
• Gnawing hard pellets keeps teeth to normal size.
• Overgrown teeth protrude from mouth.
• decreased food intake weight loss
• Clipping w/ scissors or small wire cutters cures
  problem temporarily.

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Diet

• Fed watered ad libitum
• Pelleted commercial rodent chow diets
• Automatic watering devices or water bottles can
  also be used.

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Additional Reading

• Anderson, R.S. and A.T.B. Edney. Practical
  Animal Handling. Pergamon Press, Oxford, UK.
  1991.
• Harkness, J.E. and J.E. Wagner. The Biology and
  Medicine of Rabbits and Rodents. Williams and
  Wilkins. 1995.
• Hrapkiewicz, Karen, Leticia Medina, and Donald D.
  Holmes. Clinical Laboratory Animal Medicine An
  Introduction, 2nd Ed. Iowa State University
  Press, Ames, IA. 1997.
• Laber-Laird, K., M.M. Swindle, P. Flecknell,
  Handbook of Rodent and Rabbit Medicine. Pergamon
  Press, Oxford, UK. 1996.
• Sharp, Patrick, and Marie LaRegina. The
  Laboratory Rat. CRC Press, Boca Raton, FL. 1998.