Introduction: Feathers are important body structures that act as surface insulators to reduce maintenance energy requirements and also to protect skin against abrasions and infection. The purpose of this study is to investigate the effects of methionine injection into the yolk sac on development of feather follicle in chicken embryo.

Methods: 50 fertilized eggs (weighting 50±0.4 gr) of Ross×308 broiler chicks were randomly divided into five equal groups of 10 eggs each. On day 4 of incubation, 20, 30, 40 and 50 mg of methionine dissolved in 0.5 ml of phosphate buffered saline (PBS) was injected into the yolk sac of treatment groups 1 to 4, respectively. The control group was only injected with 0.5 ml of
PBS. On the day 18 of incubation, the eggs were removed from the incubator and the embryos were killed humanely. Then, the samples were taken from the skin of thoracic region of each embryo for histometrical study.
Results: The results of this study indicated that the density of feather follicles increased significantly (P<0.05) in presence of 50 mg methionine. However, other methionine doses caused insignificant (P>0.05) increase in the number of feather follicles. A significant increase (P<0.05) was also observed in the feather follicle diameter when 40 and 50 mg of methionine were injected.
Conclusion: Administration of 50 mg methionine in 0.5 ml PBS via yolk sac in day 4 of incubation increased both density and diameter of feather follicle in chicken embryo significantly.