Background

The wild cavy or guinea pig occurs in South America from Columbia and Venezuela southward to Brazil and northern Argentina. Guinea pigs inhabit a wide variety of habitat such as rocky regions, savannas, the edge of forests and swamps. In the wild forms the hair is fairly course and long but in the domestic guinea pigs it varies from smooth and short to smooth and long to course and short in some for-ms the hair even radiates in rosettes. Although domestic guinea pigs exhibit an extremely wide range of color, the wild forms are generally gray or brownish. Guinea pigs have stocky bodies, fairly short hind legs, short ears and lack a tail. The hind feet are long with sharp claws. Guinea pigs in the wild are burrowing animals. Sometimes they live in the abandoned burrows of other animals. They generally associate in small groups, usually 5 to 10 individuals, and are always prepared to flee at the slightest indication of danger. They are nocturnal feeders and the diet consists of various forms of vegetation. South American native Indian tribes, particularly the Incas, raised them for food since their flesh is of excellent quality. During the second world war a project conducted by the Navy investigating the palatability and nutritional value of various laboratory species for the human population determined that the Guinea Pig was the most desirable of the common species. The Guinea Pig was introduced into Europe in the 16th Century by 1 the Dutch and their use spread quickly throughout the Continent. They were known by a variety of common names: "Sea Pig," "Barbary Rabbit," or "Little Sea Pig". The name Guinea Pig has become synonymous with of "experimental subject" in the that English language.

The unique characteristics of the Guinea Pig that differ from other experimental animals include the highly developed young at birth due to the long gestation period and the udder type mammary gland. The young at birth are fully developed. Their eyes are open, they are fully haired, and completely mobile. They begin eating solid food at approximately 2 to 3 days of age and can be easily weaned at 10 days. The mammary gland consists of a two section udder, each section with a single teat. Milking machines have been easily developed to utilize this udder for milk secretion research studies. The Guinea Pig is unable to synthesize an adequate supply of vitamin C and therefore must be supplied with either a supplement or a fortified diet.

Handling techniques

Guinea Pigs are probably the easiest of all the common laboratory animals to handle and restrain. They are nervous, high-strung animals compared to other laboratory rodents and are rather noisy. These sounds consist mainly of squealing, whistling, and grunting sounds. To restrain a Guinea Pig, grasp the animal around the thoracic area from above with the thumb and forefinger right behind the front legs and lift. The other hand should be placed under the Guinea Pig's hind quarters for support. Failure to restrain and support the hind quarters may result in injury to the Guinea Pig as well as injuries to the operator from scratching. Guinea Pigs rarely if ever bite. Since they have short legs and heavy bodies they are unable to climb or jump. In some instances they are housed in open-top cages or pens because of this inability to escape. IP injection of the Guinea Pig is accomplished by restraining the animal as indicated above and injecting in one of the lower quadrants of the abdomen. Subcutaneous injection can be accomplished by lifting the loose skin of the back, particularly over the neck and shoulder, and injecting under the fold. The Guinea Pig may be bled by heart puncture, anterior vena cava puncture, or small samples may be obtained from the medical canthus of the eye. Repeated blood sampling utilizing these methods can be accomplished if a suitable period of two or three days between drawings is allowed. In males the lateral vein the penis may be used for IV injections.

Experimental Uses

As the common usage of the term Guinea Pig implies, this species is widely employed as a research animal. The Guinea Pig has been used in antibody production, tumorigenesis, nutrition, genetics, radiation research, and dental studies including antibacterial action of saliva and production. The Guinea Pig is used extensively in laboratory studies of disease, nutrition and heredity, and in, development of sera. The Guinea Pig has been widely employed in biomedical research since 1780. Lavoisier used the cavy for measuring heat production. Much of the work relating to the discovery of Vitamin C, the diagnosis of tuberculosis, and the research on anaphylaxis has been performed in this species.

Strains and Sources

The majority of Guinea Pigs used in this country are random bred Guinea Pigs. Although inbreeding of Guinea Pigs was initiated at the Bureau of Animal Industry facility near Washington, D.C., in 1897, only two inbred strains, 2 and 13, still exist and these are not widely used,. The Guinea Pig, because of its large size and caging requirements, is not as widely used as the other laboratory species but does lend itself as an animal model to many research studies. When selecting a particular inbred or many research studies. When selecting a particular inbred or random bred strain of Guinea Pig for utilization, the availability and source should be closely considered. Because of its limited use, only a small number of breeders supply Guinea Pigs. The investigator is encouraged to investigate fully the suggested commercial sources before utilizing the animals these sources. As the quality of the animal received and supplied may vary greatly from one supplier to another, once a particular strain and supplier is selected they should be utilized throughout the entire study. Strain differences between individual breeders may be considerable. Therefore one supplier should be used if possible.

Guinea Pig