Congenital malformations and variations in reproductive performance in the ferret: effects of maternal age, color and parity

Demographic data of ferrets from a commercial breeding colony were analyzed for the effects of maternal age, parity and strain on reproductive performance and the frequency of gross congenital abnormalities observed at parturition. Litter size (mean +/- SEM) was found to be greatest for young, primiparous females (10.3 +/- 0.2) and decreased with advancing maternal age and parity to a cohort mean of 8.1 +/- 0.1 for third parity females 16 months of age. Age, parity or strain had no effect on 24-hour neonatal mortality (7%) or mortality from birth to weaning (20%) and an examination of the causes for death suggested that these rates can be reduced. The malformation rate from two cohorts of females whelping at different times of the year was low (less than 1.0%) and not significantly different. A higher frequency of malformed offspring was detected in females of low previous parity (0-2) than in those with three or more. Based on data obtained in this survey, the ferret would seem a valuable alternative, nonrodent species for teratologic investigations using currently recommended protocols.