1.1 BACKGROUND OF THE STUDY
The guinea pig (cava parellus), also called cavy, and the genus cavia. Despite their common name, these animals are not in the pig family, nor are they from guinea, they originated in the Andes, and earlier studies based on biochemistry and hybridization suggested they are domestic descendants of a closely related species of cavy such as Cavia aperea, C. fulgida, or c. tschudii and therefore do not exist naturally in the wild (Ounnum 2010). Guinea pigs were popular laboratory animals until the later 20th century; about 2.5 million guinea pigs were used annually in the U.S. for research in the 1960s. (Gad, 2007), but that total decreased to about 375,000 by the mid-1990s. as of 20007, they constitute approximately 2% of the current total of labory animals in the past they were widely used to standardize vaccines and antiviral agent they were also often employed in studies on the production of antibodies in response to extreme allergic reaction or anaphylaxis. The most readily identified aspect of animal sexual behavior is the mounting response. It is an essential component of the male mating pattern but frequently occurs in females, especially during estrus. In a successful mating sequence the male mounts the female from the rear. The forelegs are placed on the back or around the sides of a female with the bind legs in the ground. The posture and motion permit the male to insert the exact penis into the females vagina not all mounting, however, in oriented to the rear of the female. The male may mount the female. The male may mount ths side or head of the partner and may or any not execute peptic thrusts; but in some species, such as the rat and dog mounting by females is not restricted to any particular part of the estrous cycle. The mount executed by a female is frequently indistinguishable from that of from that of the male. Thus, the typography of the behaviour does not identify the sex of the animal. Mounting occurs between members of the same or opposite sex and across species in some instances.Male guinea pigs engage in several species. Eypical precopulatory behaviours, including nibbling the female’s fur on her head and neck, sniffing her amogenital regin,and making guttural sounds while either circling the female or shiffing his weight on his two rear feet while keeping his forepaws stationary. The male then approaches the female the rear, places his chest over the female’s back while claspring her sides, and begins petric thrusting, while usually results in a veginal intromission. Males can intromit at a rate of approximately 1 per minute, and so can ejaculate in a 15 mins test. Although a male that ejaculates with a single female usually does not reinitiate copulation within the next hour, he may copulate with a deferent tamale (Horm, 2007).