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¹ University of Nottingham, Faculty of Medicine and Health Sciences, Nottingham, United Kingdom - Enteric stress impairs poultry productivity, but the magnitude and direction of the response depend on host genotype and nutritional status. This study evaluated the effects of genotype and feed restriction on productivity and enteric resilience indicators in commercial chickens using a controlled coccidial challenge. Ross 308 broilers, Hy-Line Brown pullets, and H&N Nick Brown layers were assigned to ad libitum or restricted feeding (10% quantitative reduction) and challenged or not challenged with a 10× dose of Paracox®. Body weight, live weight gain (LWG), egg production, feed conversion ratio (FCR), lesion score, and faecal oocyst output were measured. The coccidial challenge did not produce significant differences between treatment groups. Feed restriction, on the other hand, had clear genotype-dependent effects. It reduced body weight across all genotypes, lowered LWG in broilers, reduced total egg weight in layers, improved FCR in layers but worsened it in broilers. Broilers showed higher lesion scores and greater oocyst output than pullets and layers. The results indicate that genotype and nutritional plane explained more phenotypic variation than the applied challenge, supporting a genotype-dependent interpretation of productivity and enteric resilience in commercial chickens. Keywords : Host genotype Disease resilience Feed efficiency Phenotypic variation Enteric resilience