-Growth, carcass composition and certain meat quality traits were studied in fast (F), medium (M) and slow (S) growing broilers fed with 3 regimes appropriate for each chicken type and differing on average by 418 kJ·kg -1 AMEn and 1% crude protein (P1 > P2 > P3). No significant interactions between chicken types and feed were measured before 3 weeks and after 6 weeks of age, indicating that the 3 genotypes had similar responses to the 3 diets during these periods. Before 3 weeks of age, body weight was 5% higher for P1 compared to P2 and P2 compared to P3 fed chickens for a comparable feed intake. After 6 weeks of age, a 10% reduction in feed intake occurred in P3 compared to P1 and P1 compared to P2 fed chickens for similar body weight gains. The differing responses after 6 weeks of age might be linked to high heat stress that occurred at 7 weeks of age. Between 3 and 6 weeks of age, interactions between chicken type and dietary concentration on feed intake, body weight gain characterised an "after 6 weeks of age" response for F-chickens whereas Mand S-chickens had a "before 3 weeks of age" response. These interactions might be explained by a higher sensitivity of fast-growing chickens to environmental conditions. For chickens slaughtered at market age (F = 6, M = 8 and S = 12 weeks of age), higher breast meat yield (Pectoralis major + minor) and lower abdominal fat content were observed in the F-chickens (17.2% and 2.64%, respectively) compared to the M-(15.7% and 2.86%, respectively) and S-chickens (14.4% and 3.44%, respectively; P < 0.05). Breast meat was more coloured in the S-chickens with lower L* and higher b* and a* 72 hours after slaughter than in the M-and F-chickens (P < 0.05). Dietary concentration had no significant effect on carcass composition, ultimate pH or drip loss of breast meat. Our results suggest that changes in dietary concentration alter growth performance but have little effect on carcass composition and meat quality traits. Résumé -Effet de la concentration de l'aliment sur la croissance, la composition de la carcasse et la qualité de la viande de poulets de chair à croissance rapide, moyenne ou lente. La croissance, la composition de la carcasse et quelques paramètres de qualité de la viande ont été étudiés chez des poulets à croissance rapide (F), moyenne (M) et lente (S) alimentés par 3 régimes de concentration énergétique et protéique croissante (+ 418 kJ·kg -1 EMAn et + 1 % de protéine brute, P1 > P2 > P3). Aucune interaction significative entre le génotype et l'aliment n'a été mesurée avant 3 semaines et après 6 semaines d'âge indiquant que les 3 types de poulets ont des réponses semblables aux 3 régi-mes. Avant 3 semaines d'âge, le poids vif est augmenté de 5 % avec P1 comparé à P2 et avec P2 comparé à P3 pour une consommation semblable des 3 aliments. Après 6 semaines d'âge, une réduction de 10 % de la consommation est observée entre les aliments P1 par rapport à P2 et P2 par rapport à P3 pour un gain de poids semblable avec les 3 aliments. Ces différentes réponses pe...

-Standard fast-growing (FG), 'label' slow-growing (SG), and medium growing (MG) chicken crosses were grown until their market ages: 6, 8 and 12 weeks, respectively. They were compared for carcass and muscle traits and meat processing ability. The breasts of 6wk-FG birds contained less protein, more fat and muscle fibres with larger diameters than those of 8wk-MG and 12wk-SG birds. The pH 15 and pH u values of breast and thigh muscle were the highest in the 6wk-FG and the lowest in the 12wk-SG. The latter exhibited higher breast drip loss compared with the 6wk-FG. During processing, the highest curing-cooking yields were obtained with the breast and leg meat from 6wk-FG and the lowest with that from the 12wk-SG. As a consequence of their reduced water holding ability, the processed meat from the 12wk-SG exhibited the lowest moisture and the white curedcooked meat showed the driest texture and the best slice cohesiveness. This study suggests that processing ability and processed product characteristics of breast and leg meats are greatly related to the chicken type of production, with fast growing birds being more adapted to further processing than slow growing ones in terms of profitability. deux autres types de poulets (MG et SG). Les pH à 15 minutes et à 24 h post mortem des muscles du filet et de la cuisse étaient les plus élevés chez les animaux standards (FG) et les plus faibles chez les animaux de type 'label' (SG). Les filets de ces derniers présentaient par ailleurs des pertes par exsudation supérieures à celles des filets des poulets standards. Lors de la transformation par saumurage-cuisson, les rendements technologiques les plus élevés ont été obtenus pour la viande de filet et de cuisse des poulets standards et les rendements les plus faibles pour la viande des poulets de type label. Du fait de leur pertes en eau supérieures lors de la transformation par saumuragecuisson, les produits élaborés à base de viande de poulets labels présentaient les teneurs en eau les plus faibles, et dans le cas des blancs de poulets, la texture en bouche la plus sèche et la meilleure tenue de tranche. Cette étude montre que l'aptitude à la transformation ainsi que la qualité des produits élaborés sont largement influencées par le type de poulet, la viande des poulets de type standard paraissant la plus adaptée, d'un point de vue économique, aux procédés de transformation par saumurage-cuisson.

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