LAUSR

BACKGROUND It is generally accepted that non-human primates (NHP) represent the model of choice for integrative studies of testicular function and endocrine control. However, there are many species-specific differences that necessitate identification prior to the selection of an appropriate model for these studies. In an NHP breeding facility, this opportunity of selection is usually presented during breeding periods when it is crucial to determine which individuals should be maintained as breeders. With reference to adult males and their use in breeding programs and reproductive studies, it is therefore imperative to document the normal semen and sperm values, expected seasonal changes and the variabilities found within samples and among individuals. The comparison of closely related species that differ by breeding seasonality will, therefore, highlight their value in reproductive research. METHODS Semen samples were obtained by rectal probe electroejaculation (RPE). The seminal and sperm characteristics of captive-bred Vervet monkeys (Chlorocebus aethiops) (n = 10) and Rhesus monkeys (Macaca mulatta) (n = 10) were evaluated and compared. Parameters such as semen volume, pH, sperm concentration, and sperm motility were analyzed by means of a computer-aided sperm analysis (CASA) system. RESULTS Large variations in semen and sperm parameter values indicated differences between species and samples. Monthly variations were observed for the Vervet regardless of breeding and conceptions that occurred throughout the year. In contrast, Rhesus seminal characteristics indicated a clear seasonal trend. CONCLUSION Non-human primates have long provided as research models for studying complexities of human reproductive biology. The baseline values reported from this study can be applied as guidelines during the selection of male individuals for reproductive studies. Of further interest is the comparative data on semen and sperm parameters between two congeneric species that differ by seasonal versus aseasonal breeding.