DESCRIPTION OF THE PROBLEM

The hatching of strong and viable chicks is a key factor in the performance of broilers. The appropriate management of chickens until hatching occurs in the hatchery is crucial. The final hours of the embryonic period and first hours after hatching are considered the most critical periods, and are of extreme importance for bird development. This period is character-ized by physiological events such as maturation of the gastrointestinal tract (physical and func-tional growth, increase of villi, polarization of enterocytes, and enzymatic activity) and devel-opment of the immune system (maturation of the primary and secondary lymphoid organs) [1]. The management practices adopted by the poultry industry in the early phase of a bird’s life can potentially reveal additional challeng-es to development of broilers. Factors such as breeder’s lineage, age of breeders at laying, nu-tritional condition, and size and weight of egg © 2013 Poultry Science Association, Inc. Hatch window on development of intestinal mucosa and presence of CD3-positive cells in thymus and spleen of broiler chick