A strain of Wistar albinos producing a large litter

Abstract

In the inbred stock of the Wistar albinos, a strain was separated which is remarkable in casting a large litter. While the Wistar albinos generally give a litter size of 6 or a little more in this laboratory, the number of young per litter in the new strain ranges from 8 to 13, giving the average litter size of 10. The first litter cast occurs within 3 months or a little more after birth. Then they breed at all seasons of the year, and give the litter at an interval of one or a little more. The growth of the young runs well and rapidly, showing the body weight of 50gm at 30 days of age even in the largest litter containing 13 young.
Recently, it was found that the rats of the large litter size frequently produced the tailless offspring. Attempted crosses have been made to establish the tailless strain.