The rat has short hair, a long naked tail, rounded erect ears, protruding eyes, a pointed snout with long whisker (vibrissae) and five toes on each foot. Albino rats have poor eyesight and depend on facial vibrissae and olfaction for sensory input. Rats have no gall bladder. Rattus norvegicus (brown rat) has a short tail compared to Rattus rattus (black rat), which has a much longer tail. Show Rats have a pair of incisors and three pairs upper and lower of molars. Molars are permanently rooted while the incisors have an open root and grow continuously. Due to this continuous growth of the incisors rats can have problems with incisor overgrowth when the upper and lower incisors do not meet properly (malocclusion). Malocclusion can be hereditary or follow trauma, disease or inappropriate diet and/or soft food. There is no permanent cure for overgrown teeth. The only treatment is to trim the teeth every 2-3 weeks, if malocclusion persists. Rats have a large horseshoe-shaped Harderian gland deep within the orbit. Secretions from the gland contain varying amount a reddish-brown porphyrin pigment depending on the physiologic state, age, strain and sex of the rat. The amount of secretions increases during stress and appears as 'red crusts' around the eyes and nostrils. Lifespan2.5-3.5 yearsAdult weightMales 300-500g, Females 250-300gBirth weight5-6gHeart rate330-480 beats per minuteRespiratory rate85 breaths per minuteBody temperature35.9-37.5ºCBlood volume50-70 ml/kgUrine volume3.3 ml/100g bwt/dayAllergensDander, urinary proteinBehavior Reproduction Rats have a four to five-day estrous cycle, divided into characteristic phases: proestrus, estrus, metestrus and diestrus. The stage of the estrous cycle can be determined by vaginal cytology. Ovulation occurs at the end of metestrus. Receptive females exhibit lordosis when a downward pressure is applied to the pelvis. Such females will adopt a rigid posture with the hindquarters raised. Mating leads to formation of a vaginal plug. Plugs persist for 16-24 hours and may last as long as 48 hours. Rat vaginal smear Pregnancy Rats are generally fed a diet containing low fiber (5%), protein (20%) and fat (5-10%). Feed may be pelleted or powdered. The pelleted feed is supplied as regular, breeder, certified, irradiated or autoclavable. Rats are usually supplied feed free choice and they eat 10-30 g a day (5 g/100 g body weight/day). Water is supplied free choice and they usually drink 20-50 ml a day (10 ml/100 g body weight/day). Water may be supplied using a bottle or automatic waterers, and may be further treated by reverse osmosis, ozone, ultraviolet radiation, hyperchlorination or acidification. Rats are usually provided with bedding in the shoebox cages. Bedding can be paper, wood shaving, wood chips or corncob. In very rare instances rats are housed on wire floors. Housing on wire floors must be justified and approved by the animal care and use committee. Identification Rats should always be clearly identified on cage cards indicating protocol number, strain (using standard nomenclature), sex, age, supplier, investigator and contact person. A combination of marks made by an ear punch can be used to identify rodents as indicated in the figure. Procedures performed on the animal should be clearly indicated. Individual rats can be identified using ear punches, ear tags, tattoos, fur dyes, indelible mark on tail or microchips. Sexing Return to top Rats should be acclimatized to handling (gentling) to reduce stress. Always talk quietly, move hands slowly and handle them frequently. Rats should be handled at the base of the tail using your fingers. Pick up rats by placing the hand firmly over the back and the rib cage and restraining the head with thumb and forefinger immediately behind the mandibles. Holding the rat upside down keeps it distracted and reduces the chances of biting. A variety of restraint devices are available to assist in handling rats. Blood collection Blood can be collected from several sites in the rat including tail vein, saphenous vein, retro-orbital sinus, brachial vessels, vena cava or cardiac puncture. Always ensure complete hemostasis before returning the rat to its home cage.
Administration of substances Materials to be administered to rats can be given orally e.g. in water or feed or injected systemically through a variety of routes. The average daily consumption of feed and water for an adult rat is 15-25 g and 30-50 ml respectively. The following volumes can be injected into rats safely: 2-5 ml subcutaneously, 0.1-0.2 ml intramuscularly (0.1 ml per site), 1.5-2.5 ml intravenously, 3-5 ml into the stomach and 3-5 ml intraperitonealy. Intramuscular injections are usually not recommended in rats because of the small muscle mass. A fine gauge needle should be used to make injections in the anterior thigh muscle. It is good practice to use a new needle each time you perform an injection.Intramuscular injection in a rat Gavage Gavage needles Estimating the length of needle to be inserted into the animal Inserting a gavage needle into a rat Subcutaneous injections Intraperitoneal injections Picture demonstrating intraperitoneal injection in a rat Intravenous injections Tail vein injection demonstrating warming the tail to dilate the vessels and making the injections Acute pain Chronic pain Anorexia (no fecal pellets)Decreased body weightDecrease in appetite (few fecal pellets)Reluctance to moveRubbing or scratching surgical siteChange in behaviorBiting or shaking affected body partPoor groomingVocalizationChange in bowel or urinary activityRestlessnessRough hair coatPorphyrin discharge (red-brown pigment around eyes and nostrils)Increased respirationPain relief Anesthesia Euthanasia Diseases of rats are usually handled as a herd (colony) health problem rather than on an individual animal basis. In most cases the goal is to prevent introduction of a disease into a colony than to treat individual animals. Disease prevent is practiced by institution of a health monitoring (sentinel) program based on serological and microscopic diagnosis of problems in a representative sample of animals. Due to the widespread movement of animals all over the world with advent of genetic manipulation of animals, the possibility of introducing disease agents in a colony has markedly increased. The expanded use of genetically modified and immunocompromised animals greatly exacerbates the problem. Furthermore the practice of transplanting tumor material into animals provides a portal where these agents can be introduced into animal, especially if the tumors are not screened for adventitious infectious agents. Some important rat diseases are discussed below to draw attention to the need to adhere to practices recommended by the veterinary staff to avoid these diseases. For additional information see Implications of infections agents on research results and Opportunistic Infections in Laboratory Rodents. Which common health condition of rats is a fungus?Ringworm. Ringworm is caused by fungi called dermatophytes that parasitize the skin. The infection is spread by direct contact or by contaminated bedding, litter, or cage supplies, and it can infect humans and other animals. Ringworm occurs infrequently in rats.
Which description is not true about static caging for rats?`Which description is NOT true about static caging for rats? Urine and feces can fall through perforations in the bottom of the cage. Which common health condition of rats is a fungus? Barrier facilities should only contain static cages contained in ventilated racks.
Which statement is true regarding care procedures for rats undergoing surgery?Which statement is true regarding care procedures for rats undergoing surgery? During the procedure, rats should be monitored mainly for anesthesia, body temperature, and cardiovascular and respiratory function.
Where is porphyrin produced in the rat quizlet?Rats have Harderian glands which are located behind each eyeball. They produce a secretion that has a red-tinge to it (porphyrin) that can cause the rat to produce "red tears".
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