Subsequently, post-weaning observations clearly indicated that the 'small' mice had, in-effect, caught up with respect to their relative physical characteristics. Specifically, when the animals were assessed again at 8 weeks of age, there were no significant differences between groups for most of the parameters observed (Table 9 ). This suggests that in offspring nursed by a-casein deficient mice, general development of pups is less impaired than what would be expected from their significant growth retardation which has persisted throughout their life so far (currently the mice are almost 2 years old).