Abstract
This study was conducted to evaluate the effects of heating hatching eggs on the number of day-old chicks, egg temperature and egg weight during extended storage, and to provide basic information for improving hatchability to livestock producers. Eggs (Hy-line) were subjected to the following treatments: "control": eggs were maintained in an incubator after storage for 8 days; "T1": eggs were preheated for 8 hours at $23.9^{\circ}C$ after storage for 8 days in a hatchery; "T2": eggs were initially heated for 8 hours at $37.8^{\circ}C$ in an incubator and then preheated for 8 hours at $23.9^{\circ}C$ in a hatchery after storage for 8 days. The results were as follows: First, at the end of the experiment, the total number of day-old chicks was higher in T1, followed by T2 and then the control. This indicated that chick hatchability may be improved when eggs are preheated. Second, compared with the control, the number of day-old female chicks was expected to be higher in treatments with pre-heating; however, the results indicated the opposite effect. Third, as storage time lengthened, the factor that influenced preheating (the main effect and interactions) was not egg weight but egg temperature measured in the upper, middle and bottom parts of incubator. The temperatures recorded in all treatments ranged from 37.97 to $38.40^{\circ}C$ in the upper parts of incubator, 37.80 to $38.26^{\circ}C$ in the middle parts of incubator, and 37.94 to $38.59^{\circ}C$ in the bottom parts of incubator over storage. In conclusion, preheating was very effective in improving hatchability, and egg temperature was the main factor affecting preheating and hatchability.
