After hatch, broiler chickens may have immediate (early nutrition) or delayed (delayed nutrition) access to feed and water. In several countries, early nutrition is frequently applied to improve broiler growth performance and health. The aim of this doctoral thesis was to study early and later life effects of early nutrition compared with delayed nutrition on growth performance, intestinal integrity, and the immune system. We concluded that early nutrition can be applied to induce the earlier onset of post-hatch intestinal development, but intestinal integrity is not permanently affected by early nutrition. Higher levels of systemic antibodies up to 7 days of age in early nutrition broilers, may imply a better first line of defense during the first week of age. However, broilers receiving early nutrition did not benefit from this altered immune development in later life under both high or low sanitary rearing conditions.