Advances in reproduction in captive, female great apes: Value of biotechniques

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Abstract
Most of the progress in female great ape reproduction has focused on monitoring ovarian and endocrine activity. Perhaps of more importance has been the gradually evolving interest and willingness to consider biotechnology as a potential, viable approach for enhancing reproductive performance. Artificial insemination (AI), in vitro fertilization (IVF), and embryo transfer offer an array of possibilities for combating infertility and understanding the fundamental differences and similarities among great ape species. Multidisciplinary efforts have assessed reproductive competence, from the simple (i.e., perineal tumescence and urinary occult blood in chimpanzees) to the complex (i.e., ovum recovery and IVF following exogenous hormone treatment in chimpanzees and gorillas). Hysterosalpingography and laparoscopy have been used to determine uterotubal patency and to identify pathological conditions in gorillas. Assays for steroid metabolites in serial urine samples, to permit accurate assessments of ovarian cyclicity, have been developed and validated for all great apes species. Stimulation of follicular recruitment and maturation has been achieved following administration of clomiphene citrate (chimpanzees and gorillas) and human menopausal gonadotropin (gorillas). Clomiphene citrate and human chorionic gonadotropin have been used to regulate ovulation for the AI of chimpanzees. Pregnancies have resulted in chimpanzees and gorillas following AI using fresh and cryopreserved/thawed semen; however, conception rates vary. Embryos have been nonsurgically recovered from chimpanzees after timed matings and follicular oocytes have been recovered from chimpanzees and gorillas by transabdominal laparoscopy after exogenous hormone treatment. To date, although in vivo matured ova have been fertilized in vitro using homologous sperm in chimpanzees and gorillas, no great ape offspring have been born from transferred embryos produced by in vitro or in vivo fertilization. A review of the many remaining problems suggests the need for more basic studies of ovulation induction, ovum and sperm requirements in vivo and in vitro, and the effects of animal manipulation (anesthesia, surgery, and other stressors) on the ability of the female to ovulate and sustain pregnancy. Especially important are more assessments to identify reproductively competent individuals so that these females can be placed with breeding males while subfertile or infertile animals are designated for intensive artificial breeding research.