Objectives:
Early malnutrition is a highly prevalent condition in developing countries. Different rodent models of postnatal early malnutrition have been used to approach the subject experimentally, inducing early malnutrition by maternal malnutrition, temporal maternal separation, manipulation of litter size or the surgical nipple ligation to impair lactation. Studies on the behaviour of (previously) malnourished animals using animal models have produced sometimes contradictory results regarding the effects of early postnatal malnutrition and have been criticized for introducing potential confounding factors.
The present paper is a first report on the behavioural effects of early malnutrition induced by an alternative approach: mice nursed by a-casein-deficient knockout dams showed a severe growth delay during early development and substantial catch-up growth after weaning when compared with animals nursed by wild-type females.

Methods:
Established behavioural tests were used to study the consequences of early postnatal malnutrition on mouse pups at weaning and after partial weight recovery.

Results:
Despite the impaired growth, the only behavioural difference between malnourished and normally growing animals was found in exploratory behaviour during acute malnutrition at the time of weaning. After partial catch-up in weight early protein malnourished animals showed no indication of lasting effects on general activity, emotionality and exploration, memory, and pain reactivity.

Discussion:
These results suggest that the role of early nutrition on behavioural development after recovery in animal models may have been overestimated. Further careful examination of this animal model in terms of maternal care and offspring behaviour will be necessary to confirm if mice nursed by a-casein-deficient dams offer an alternative to existing models while eliminating potential confounding factors.