The feed efficiency is one of the main objectives in livestock production because feeding is the highest cost in animal production. The objective of this study was to compare the feed efficiency in two divergent lines for the birth weight environmental variability in mice. The results showed that the weekly feed intakes were lower in the low line than the high line in some periods. These differences could be related with the lower weight in the low line. The cumulated feed intake index didn’t show significant differences between lines. The robustness of low variability animals seems not to produce differences regarding feed efficiency, but probably low variability animals could respond better to an environmental challenge taking benefit to increase its survival.