The sex ratio of CFE rats as born is approximately 1:1, but the demand is usually for many more males than females. Litter size as born is variable, with resulting variation in weight for age at weaning and subsequently. The average litter size born is lower than that which the dams are capable of rearing. By a system of crossfostering pups at about two days of age, and killing surplus female pups at this age, litter size may be standardized, the sex ratio of animals raised can be adjusted to the demand, and larger litters can be reared.
References
1.
Carworth Europe handbook (1967). Huntingdon: Carworth Europe.
2.
Lane-PetterW., BrownA. M., CookM. J., PorterG., & TufferyA.A. (1959). Measuring productivity in breeding of small animals. Nature, Lond.183, 339.
