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Abstract This experiment was conducted to assess the hypothesis of influencing the temperature changing during incubation on some hatching traits, spread of hatching, and some chick’s quality. A total of 440 ROSS 308 broiler hatching eggs (63.54 + 2.07 g) from 34-week old broiler breeders, randomly distributed into five treatment groups of 88 eggs each, the first, second, third and fourth group were subjected to change in temperature (39.5 °C, 55% RH) at 7 th , 10 th , 13 th and 16 th day of incubation respectively for 12 hours; via transferring the treated eggs from first incubator to the second, after that the thermal treated eggs were returned to the first incubator with the fifth group (control treatment) under optimal incubation conditions (37.8 °C and 55% RH) throughout the incubation period (1-18 d). Treated eggs with increasing temperature during incubation period significantly decreased the percentage of chick’s hatched in last phase of hatching windows in comparison with the control group, also, significant increase in early embryonic mortality percentage was noticed in 7 th and 10 th day group, whereas, changing in temperature during incubation caused significant differences in chick’s length and body free yolk (%) and yolk (%) for treated groups.
Alhadeethi et al. (Mon,) studied this question.