The effect of light and specific gravity on embryo weight and embryonic mortality

Eggs from Single Comb White Leghorn chickens were divided into two approximately equal groups with the range of specific gravities being present in each group. One group was incubated in a darkened Humidaire Hatchett while the other was incubated in an identical machine equipped with two 20 Watt fluorescent tubes which produced 8.3 X 10(3) ergs/cm.2-sec. at the surface of the eggs. The recommended temperature and humidity settings were used in both machines. After 7 days of incubation embryos from the lighted incubator were significantly (P less than .01) larger than those incubated in the dark. There were significantly more live embryos from low and high specific gravity eggs in the light than in the dark. There was no difference in embryonic mortality between groups for the eggs with intermediate specific gravities. Embryos from White Leghorn eggs incubated in the presence of light were significantly (P less than .01) larger on each day of incubation from day 2 through hatch. Eggs incubated in the lighted incubator hatched at 18 and 19 days and produced larger chicks than those hatched at 20 and 21 days in the dark.