A simple method for repeated in vivo sperm collection from laboratory mice.

PURPOSE: Mouse spermatozoa for archiving laboratory mice or for in vitro fertilization (IVF) are routinely obtained from the cauda epididymis of adult males sacrificed for this purpose. To avoid the death of the donor, we tested whether a precisely timed interruption of the mating act could be used for repeated sperm collection from laboratory mice. METHODS: Sperm donors (B6D2F1) were mated with a receptive female, and mating behavior was observed. The stud was separated from the female 1-2 s after the onset of the ejaculatory shudder. The ejected copulatory plug with the yellowish viscous ejaculate was carefully removed from the penile cup. RESULTS: A total of 80 ejaculates were successfully obtained from 100 ejaculations. The latency to first mount was 1.1 ± 1.1 min (mean ± SD) and to ejaculation 8.1 ± 4.7 min. The average number of mounts to ejaculation was 10.5 ± 5.8, and the mean number of spermatozoa per collected ejaculate was 1.86 ± 1.05 × 10(6). An average fertilization rate of 76% was observed after IVF. CONCLUSIONS: Separating the stud from the female just before ejaculation is feasible, easy to learn, and requires no special equipment. The sperm count of collected ejaculates is lower than natural ejaculations, but higher than previous in vivo sperm collection methods achieved. We recommend this simple sperm collection method in mice, especially when the donor cannot be sacrificed and/or repeated sperm collection from the same animal is required for experimental purposes.