Comprehensive Rodent Service
Breeding Systems
The two most commonly used methods for breeding rodents are monogamous and polygamous (harem) breeding. Each has its advantages and disadvantages which should be considered when establishing your colony.
Monogamous Breeding
A monogamous system consists of one male and one female permanently housed together. It will produce the maximum number of litters per female in the shortest time frame, by utilizing the female's post-partum estrus (~12h post partum). Record keeping is easy with this method. However, it requires a larger population of males to be maintained.
Harem Breeding
Harem breeding utilizes on male to breed several females. It is the most efficient for space and utilization of males, but it makes record keeping more difficult. Pregnant females must be separated from the group prior to delivering their litters, this is in accordance with the Mouse Housing and Cage Density Policy. By following this practice it will also enable the investigator to identify exactly which mother has produced the litter. The female is returned to the male cage after the litter is weaned. Although this method requires fewer males to be maintained it is more labor intensive to manage the colony and it does not make use of the post-partum estrus in the females.
Timed Mating
For certain experimental conditions it may be necessary to do "timed matings". The male and the female are housed together overnight. In the morning the female is checked for the presence of a vaginal plug. This plug, a mixture of the secretions of the vesicular and the coagulation glands, indicates that a mating has taken place. Predictability of pregnancy resulting from these matings is strain dependant, but in general is very high. There are two methods to synchronize the estrus of the female mouse which increase the chances for mating on a specific day:
- Whitten Effect
- Female mice housed in groups without the presence of males are anestrous (Lee-Boot
Effect). Exposure of anestrous female mice to pheromones in the urine of male mice
initiates the estrous cycle and most females are in estrus during the third night after
exposure (Whitten Effect).
Group-housed females are moved to cage with a male. The cage is partitioned, so that the male cannot reach the female, but there is olfactory contact. On the third day the partition is removed and the female is checked for a copulatory plug on the morning of the fourth day. - Super-Ovulation
- Female mice are injected with follicle stimulating hormone (PMSG, 5 I.U., IP). 46-48 hours later they are injected with lutenizing hormone (HCG, 5 I.U., IP) and mated to a male. The females are checked for a copulatory plug the following morning.
