Guinea pig (Cavia porcellus), guinea pig is native to South America. Taxonomically, it belongs to the class Mammalia, order Rodentia, family Guinea pig, and genus Guinea pig. Experimental guinea pigs are domesticated and bred from wild guinea pigs, also known as guinea pigs, guinea pigs, etc.

(1) Biological characteristics

1. General characteristics and living habits

(1) Guinea pigs have a short and thick body, a big head, short ears and limbs, no tail, and are covered with hair. There are four toes on the forelimbs, three toes on the hind limbs, and nails on the ends of the toes.

(2) Guinea pigs are herbivorous animals and like to eat tender grasses or dry feed that are rich in fiber.

(3) Guinea pigs are timid, docile, and extremely sensitive to external stimuli. Like a quiet, dry, clean environment. Sudden sounds and vibrations can cause the pregnant rats to run away and even cause miscarriage.

(4) Guinea pigs like to be active and live in groups.

(5) Guinea pigs have well-developed hearing and can recognize a variety of different sounds.

2. Anatomical characteristics

(1) Skeletal system: The skeleton of the whole body is composed of skull, trunk bones and limb bones. Incisors grow throughout life.

(2) Digestive system: The stomach wall is thin, the stomach capacity is 20~30ml, the intestinal tube is about 10 times the body length, and the cecum is well developed. The liver can be divided into five lobes and has a gallbladder.

(3) Respiratory system: The tracheobronchi are underdeveloped, with only tracheal glands in the larynx and none below the bronchi. The lungs are divided into 7 lobes, 4 lobes in the right lung and 3 lobes in the left lung.

(4) Lymphatic system: Guinea pigs have a relatively developed lymphatic system and are extremely sensitive to invading pathogenic microorganisms.

(5) Nervous system: The brain matures during the 42nd to 45th day of the embryonic period.

(6) Reproductive system: Female rats have two completely separated left and right uterine horns, and a pair of mammary glands are located in the groin of the rat. Females have a nonporous vaginal closing membrane that is open during estrus and closed during non-estrus. Males have a raised scrotum on both sides that contains the testicles.

3. Physiological characteristics

(1) Sexual maturity is early, female mice are 30 to 45 days old, and male mice are 30 to 45 days old. Rats become sexually mature at 70 days of age. The sexual cycle is 13 to 20 days, the gestation period is 65 to 70 days, usually 3 to 4 babies are born, and the lactation period is 2 to 3 weeks. Newborn cubs weigh about 80g. They can move around immediately after birth, have fur, open eyes and ears, and have incisors. They can feed themselves after a few hours. Generally, guinea pigs weighing 200g to 250g are used for experiments.

(2) The life span is generally 4 to 5 years, and the longest can be 8 years. Growth and development are rapid.

(3) The red blood cell index is lower than that of other rodents, and the morphology of peripheral blood and bone marrow cells is similar to that of humans.

(4) The ability to automatically regulate body temperature is poor, and the optimal feeding temperature is 18~22℃.

(5) The body lacks L-glucolactone oxidase and cannot synthesize vitamin C by itself. The required vitamin C must come from feed.

(2) Application in biomedical research

1. Pharmaceutical research: The skin of guinea pigs is sensitive to poisonous stimulation. Skin irritation experiments are carried out and are often used to detect the effects of local skin poisons. Test; drug efficacy evaluation experiment.

2. Immunology research: complement and allergic reaction research.

3. Infectious disease research: Guinea pigs are highly sensitive to Mycobacterium tuberculosis and are the best animals for isolation, identification, disease diagnosis and pathological research of Mycobacterium tuberculosis.

4. Otology research: such as the impact of noise on hearing, research on ototoxic antibiotics, etc.

5. Nutritional metabolism research: Since guinea pigs cannot synthesize vitamin C in their bodies, they are also very sensitive to its deficiency and will develop a series of scurvy symptoms.

(3) Commonly used breeds and strains

1. British guinea pigs: belong to a closed group. Its fur colors include black, white, brown, etc. This kind of guinea pig has strong fecundity and docile personality. It responds well to experiments and is mostly used in research on infectious diseases.

2. FMMU albino guinea pig: The whole body is white and the eyes are red. Since this kind of guinea pig has better blood vessels and immune response, albino guinea pigs must be used in acute and chronic skin toxicity tests and skin irritation reactions. This guinea pig is also widely used in pharmacological and toxicological research.

(4) Feeding and management of guinea pigs

1. Gender identification: Grasp the guinea pig's neck with one hand, and peel off the skin near the genital hole with the other hand. The male will be exposed in the round hole. The protrusions of the sexual organs, while females show a triangular gap. In addition, adult females have a pair of slender nipples.

2. Breeding environment: Guinea pigs have good hearing and are timid and easily frightened, so the environment should be kept quiet and open, and the noise should be below 60dB.

3. Cage padding: Cage types include ground fences, drawer boxes, wire mesh bottoms and plastic cage boxes with solid bottoms. Guinea pigs cannot climb heights and have poor jumping ability. The traditional way of raising guinea pigs is to raise them in cement or wooden ground pools with a surrounding height of 40cm. Generally, no cover is needed. When raising in ponds or cages with solid bottoms, disinfected bedding is generally required. The litter should be soft shavings without mechanical damage. Small hard shavings, flakes, and sawdust can stick to the genital mucosa, affecting mating, and even damage the genitals, making guinea pigs infertile. Powdered litter can easily cause respiratory diseases and should not be used.

4. Feeding and drinking water: Guinea pigs are animals fed crude fiber, and vitamin C cannot be synthesized in the body, so it must be supplemented in the feed.