Effects of egg weight and light sources during incubation period on embryonic development and post-hatch growth of Japanese quail (Coturnix japonica)

This experiment was conducted to evaluate the effects of egg weight and different light sources during incubation and their interactions on embryonic development, hatchability (%) and post-hatched growth of Japanese quail chicks. A total of 700 fertile eggs were assigned into two categories; the first was incubated in white fluorescent (FL) light and the second was set at incandescent (INC) light and each group was classified into two subgroups according to egg weight into small (10.00-12.67 g) and large (12.68-15.30 g) eggs. Results showed significant differences between incubated groups on most of the examined traits. The relative embryonic weight at day 14 of incubation and the hatchability were significantly higher in the FL group than that in the INC group. Average chick weight at hatch and at 6 weeks of age increased significantly with the increase in egg weight under both light sources. Chicks hatched from large eggs under FL light had higher weight gain and feed intake, but the mortality rate of chicks was not affected by the treatments. There was a clear light source x egg weight interaction for the relative embryonic weight, hatchability and embryonic mortality. Higher hatchability and relative embryonic weight were obtained from the small eggs incubated under FL and INC light, respectively, while birds hatched from the large eggs incubated under FL light showed the best weight gain and feed conversion ratio. Furthermore, FL chicks exhibited higher (P <= 0.01) plasma triiodothyronine hormone (T-3) level, total protein, albumin, globulin, glucose, cholesterol and triglyceride concentration of embryos than those measured in the INC group. We conclude that higher hatchability and better growth performance during both embryonic life and post-hatch might be attributed to the role of the light source on physiological and metabolic processes. Therefore, it is recommended to incubate larger eggs of Japanese quails under FL light as the best condition to achieve high production parameters.