Effect of natural litter size on the post-natal growth in CF rats

The litter effect among natural litters (with minimal differences in size i.e. 6, 8 and 9) on the growth was studied in CF rats from post-conception (PC) day 22 to 90 by somatometric techniques. Body weight was found to be significantly low in larger litters up to PC day 50 although the difference persisted numerically until PC day 90. Crown-rump length, tail length and patellocalcaneal length were significantly (less than 0.001) reduced in larger litters. Growth rate curves substantiated these observations. Since the differences in size among the three groups of litters were too small to cause any nutritional deprivation and the natural potential for growth was not altered, differences in mother-offspring and/or offspring-offspring emotional interactions could be the possible factor responsible for the growth rate differences.