Abstract
Litters of 12 pups produced the optimum results for survival (P<0·005) and for weaning weights (P<0·05) when compared with litters of 8 and 10 pups. This number is similar to the normal litter size and normal number of teats in rats. In our study, the normal litter size was X = 12·5. Our results were obtained under favourable conditions without disturbing the animals and facilitating access to food and water for the mothers and pups.