The few days before and after hatch is a critical period for the development and survival of commercial broilers. Glycogen reserves in the chick embryo are significantly depleted during the perihatch period in order to meet the high energy demands during the process of emergence (Uni and Ferket, 2004). The immediate posthatch period is characterized by a transition from the use of lipid-rich yolk as the nutrient source to exogenous feed rich in carbohydrates and proteins. This transition is accompanied by rapid physical and functional development of the gastrointestinal tract (Sklan, 2001). The accelerated rate of development posthatch is reflected in the several-fold improvement in the development of the gastrointestinal tract and organ growth which will allow for a more efficient uptake of nutrients for muscle development. During late embryogenesis, solutions administered into the amniontic fluid (in ovo feeding) are consumed by the embryo, digested, and absorbed by the embryonic intestine prior to pipping (Uni et al., 2005). In ovo feeding of supplemental nutrients may help to overcome the constraint of limited egg nutrients (Foye et al., 2006). The objective of this experiment was to evaluate the effects of in ovo feeding of carbohydrates and threonine, alone or in combination, on growth performance of broiler chicks from 1 to 42 d of age.