A method for incubating avian eggs, comprising: a. introducing avian eggs into an incubation chamber having an oxygen-containing atmosphere； b. subsequent to ‘；a’；, incubating said eggs in said incubation chamber for a period of time that is not less than 25% of the natural incubation period of said eggs； c. during said period of time of the incubating, changing an orientation of said eggs at a frequency of not less than once every two days； and d. during said period of time of said incubating, varying a temperature of said atmosphere in said incubation chamber at a frequency of not less than five times a day, the varying comprising: increasing the temperature of the atmosphere from a first temperature to a second temperature, the difference between the first temperature and the second temperature being not less than 1.0° C.； and reducing the temperature from the second temperature to a third temperature, the difference between the second temperature and the third temperature being not less than 1.0° C. wherein the rate of said increasing the temperature of the atmosphere is not greater than 0.9°/5 minutes； and the rate of said reducing the temperature of the atmosphere is not greater than 0.9°/5 minutes.
