Abstract
According to historical records the NIH/Ola strain was developed from outbred 'Swiss' mice imported into the USA by Dr C. Lynch in 1926. A comparison of biochemical markers in strain NIH/Ola and other strains such as SJL and SWR derived from the same foundation stock supports the historical records. Data on litter size, length of gestation, bodyweight to 70 days of age, and reproductive performance when housed in polygamous groups of up to 10 females per male were compared with similar data on inbred CBA/CaOla and CS7BL/10ScSnOla mice. NIH/Ola inbred mice had an exceptional reproductive performance, producing about 1·8 young weaned/female/week when housed as monogamous pairs over a period of 20 weeks, compared with less than 1·0 young/female/week with the other 2 strains. NIH/Ola mice were also extremely tolerant to mating in polygamous groups of up to about 8 females per male. Mating ratios of over 2-3 females per male resulted in a marked decline in the total number of litters produced per female in C57BL/10ScSnOla and CBA/CaOla, but this reduction was not nearly so marked in NIH/Ola. It is concluded that the NIH/Ola inbred strain may be particularly useful in studies such as teratology where a high reproductive performance needs to be combined with the advantages of a fully inbred strain.