The incubation period (21 d) represents about 37 % of the entire lifespan of the modern broiler bird. Organ and overall body development during incubation are related to the final market weight. The technology for in ovo feeding has been largely developed (Uni and Ferket, 2003) but the uptake rate is slow. This may partly be due to lack of suitable nutrients, which not only promote pre- and post-hatch growth but can support good hatchability. In the present study, 0.5 ml of a solution of betaine was injected into standard size 18 d embryonated broiler eggs at 10, 50, 100 and 200 mg betaine per egg. There were un-injected control eggs and sham control eggs injected with 0.5 ml Milli-Q water. The eggs were re-set to hatch and chicks were maintained in their respective groups and fed on a standard diet (based on sorghum and maize) to 21 d of age.