Collection of semen from marmoset monkeys (Callithrix jacchus) for experimental use by vaginal washing

Assisted reproductive techniques make an important contribution to the conservation of endangered primate species. In our laboratories marmoset monkeys (Callithrix jacchus) are used as a model species for developing assisted reproductive technologies for New World primates. The studies require a reliable method for collecting functional sperm from these small animals. For this purpose a minimally invasive procedure, vaginal washing after natural mating, was evaluated for its suitability as a routine method of obtaining ejaculated sperm of high quality. The objective of the first series of tests was to identify a behavioural pattern which was easily discernible by the observer and provided a reliable indication that ejaculation had occurred. In a second series of tests the influence of length of separation of the male prior to copulation on the quality of the ejaculate was evaluated. Six adult ovariectomized and five adult intact females were used for vaginal washing, while their mates served as donors of ejaculates. Matings at specific times were achieved by separating the males from their females for a certain time period and subsequently introducing either their own mates or unfamiliar males to the females. After each observed mating vaginal washing was performed on the unsedated females. The seminal samples obtained were analysed for sperm concentration, the proportion of motile sperm and the proportion of live sperm. The results have shown (a) that ejaculation was indicated with a reliability of 86.1% by the behaviour of the female, who terminates a copulation by moving away from her partner; (b) that separation of the male for up to six days had no negative effect on the sperm quality; (c) that the sperm samples were of high quality. Vaginal washing after natural matings appears to be a practical, reliable and gentle method for routinely collecting ejaculates from marmoset monkeys and possibly other New World primates.