Poultry production currently relies on the use of soybean as the main protein and energy source. Reducing its proportion in poultry diets and partly replacing it with local feedstuffs would improve sustainability by reducing dependence on importations and the environmental impact of production. In this study, we evaluated the impact of replacing soybean by sunflower meal, fava bean, canola meal, and dried distillers’ grains with solubles on the performance of rapid- and slow-growing chickens. Animals were reared in groups and on the floor. Individual body weight and feed intake data were collected throughout each animal’s life thanks to an electronic feed station. At 5 weeks (for broilers) and 12 weeks (for slow- growing chickens), the birds were slaughtered to obtain carcass composition and meat quality data. Adaptation to the alternative diet was studied separately for each genotype. Firstly, we did ANOVA with diet effect on daily data of individual body weight, feed intake, and feed conversion ratio. Secondly, the variability of performances within the group was studied by ANOVA with effects of diet, period and their interaction. Finally, the correlations between daily performances and final performances at slaughter were calculated to understand the construction of final phenotypes and to identify early indicators of final performances. The results first showed that the animals adapted well to the alternative diet, mean daily and final performances being mostly similar between the two diets for both genotypes (<3% on final BW). However, daily observations highlighted the critical importance of periods around dietary transitions by showing impacted performances for both genotypes. For example, FCR of LR-AD was 12 to 14% lower during the three days after transitions than during the three days before. It underlined the fact that adapting management of the batch to the alternative diet would be necessary. Correlations between daily and final performances showed that the slaughter performances of rapid-growing chickens were mostly determined by body weight whereas the main criterion was cumulative feed conversion for slow-growing chickens. These correlations also suggested that reserve making might be modified with the alternative diet, with rapid-growing chickens making more glycogen reserves and less fat reserves.