Some reproductive studies in the baboon.

A captive colony of baboons has been used for three decades for various reproductive studies where application of findings to human therapeutics was desired. The characteristics of the menstrual cycle in baboons are very similar to those of women, except that of the baboon is slightly longer and there is a lower luteal phase concentration of oestradiol. The duration of pregnancy in baboons is about two-thirds that of humans but patterns of oestrogen and progesterone secretion are virtually identical. The principal oestrogen produced by the pregnant baboon is oestrone, while oestriol is the most abundant in human pregnancies. Chorionic gonadotrophin (CG) is elevated significantly only in the first trimester of a baboon pregnancy, while human pregnancy concentrations of this hormone are about one-third of the first trimester level in the second and third trimesters. Breeding success of baboons in captivity depends on care being taken to cull infertile animals from the colony prior to commencing matings. Under optimal conditions, fertility rates can reach nearly 80%. Female baboons have been successfully used to gain insights into antifertility effects of contraceptive vaccines directed against CG, spermatozoa and ovum antigens. Extensive use of the colony for developing a human chorionic gonadotrophin (HCG) antifertility vaccine has been invaluable for progress in this field. Other pharmaceuticals and devices have been successfully tested in baboons, but costs and mandated regulations for the management of these nonhuman primates have made their current use in meaningful studies extremely difficult.