Six hundred forty day old chick (Ross-308) were divided into 80 groups of 8 birds each. A 4X4 factorial arrangement in a complete randomized design experiment was used to study the effects of four levels of energy (2900, 3000, 3100 and 3200 Kcal/kg) and four levels of protein (17, 20, 23 and 26%) on performance and humoral immune responses of broiler chickens. Each diet was randomly fed to five groups of chicks from 5 to 35 d of age. Group weight and feed intake were recorded every 5-day lymphiod organs and liver weight were determined at 10, 15, and 20 d. Whereas there are negative phenotypic contribution between immunocompetence and rapid growth in chickens, rapid growth decreased immune responses. This means that birds were selected for rapid growth but not for enhanced immune responses.

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