Female reproduction characteristics in a large-scale breeding colony of cynomolgus monkeys (Macaca fascicularis).

We studied two mating systems for a large-scale breeding colony of cynomolgus monkeys: (i) a 3-day timed system that keeps one female and one male together in a cage for 3 days beginning 11 days after menstruation, and (ii) a 7-day timed system beginning 9 days after menstruation. Regardless of the mating system used, we propose a practical definition of an infertile female as one that does not become pregnant in up to six pairings. If we eliminate these animals from the breeding colony, the pregnancy rates would be 3.6 times higher. Eliminating infertile females from a breeding colony is important in order to save labor, time and cost and to maintain a healthy breeding colony.