This study proposes an indirect approach to estimate the robustness of Charolais beef cows in a changing nutritional environment. The approach quantifies the modulation of energy allocation between functions over a productive cycle. The residual energy (E resid ), defined as the net energy intake minus the energy secreted in milk and deposited in tissues was used. Forty Charolais suckling cows, differing in their body condition at (moderate: 2.0 ± 0.04 vs fat: 2.8 ± 008) were submitted to two nutritional trajectories : one trajectory corresponding to a non limiting energy level (NL) vs one variable trajectory characterized by a feed restriction period (120 d post-partum) followed by a refeeding period at grass (70 d). The milk production was similar between the groups of cows. E resid was 20% lower in cows experiencing a variable trajectory in comparison with those experiencing an NL trajectory whatever their body condition at calving. At the end of experimentation, body weight and condition were similar between groups. These results suggest that variations in E resid reflect the ability of cows to give priority to production functions when facing a changing nutritional environment and may be viewed as an indirect criterion of robustness.