Genetic engineering of miniature pigs has facilitated the development of numerous biomedical applications, such as xenotransplantation and animal models for human diseases. Manipulation of the estrus is one of the essential techniques for the generation of transgenic offspring. The purpose of the present study was to establish a useful method for induction of the estrus in miniature gilts. A total of 38 pubertal miniature gilts derived from 4 different strains were treated with exogenous gonadotropins. Estrus and ovulatory response were examined after treatment with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) as 200IU PMSG and 100IU hCG, 300IU PMSG and 150IU hCG, or 1500IU PMSG only, followed by 100, 150 or 750IU hCG 72h later, respectively. The optimal protocol was determined to be the combination treatment of 200IU PMSG and 100IU hCG followed by 100IU hCG. The administration of 200IU PMSG and 100IU hCG was effective in inducing estrus regardless of the strain, although there was a strain difference in the ovulatory response. These results indicate that treatment with a low-dose combination of PMSG and hCG provides one of the simplest methods for induction of estrus and ovulation in pubertal miniature pigs.
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