Simplified and practical procedures for collecting macaque semen containing little coagulum and for preserving semen in vitro for a long period were studied with cynomolgus monkeys that had proved fertile.
The semen ejaculated into the vagina of the female mated was taken by aspirating with a pippet. A greater part of the semen taken in this way was usually represented by fluid.
The semen thus obtained was diluted with a glycerolated extender containing lactose, glucose, raffinose and egg-yolk. The most adequate concentration of glycerol in the extender was 5%. Then, about 0.1 ml of diluted semen was frozen into a pellet form on a dry-ice block after about 30-min pre-cooling to 4C. The frozen pellet of semen was preserved in a liquid nitrogen container. The quality of the preserved semen was evaluated by its spermatozoal survival rate and motility; the semen has successfully been preserved for at least 20 weeks until the time of preparing this paper, maintaining about a 60% level of the spermatozoal survival rate.