Effect of high shell temperature and position in the incubator on embryonic mortality and hatchability of fertile broiler eggs

The effects of high egg shell temperature (EST), egg position in incubator and egg weight on embryonic mortality and hatchability of fertile eggs from a broiler parent stock were investigated in this study. Egg weight was determined in a total 1920 hatching eggs, which were obtained from middle-aged (39 weeks old) Ross 308 broiler breeders. These eggs were classified according to weight as light (60.3 +/- 0.04 g), medium (64.4 +/- 0.0 g) and heavy (68.8 +/- 0.1 g). They were randomly set in trolleys of 4 identical incubators sorted as near the heather side -door side, humidifier side opposite side and top - middle - bottom. The incubators were operated from the beginning to the end of the incubation period to provide 4 different high EST values of 100.5 degrees F, 101.0 degrees F, 101.5 degrees F and 102 degrees F. At the end of the hatching period, data on embryo mortality and hatchability of fertile eggs were examined. It was found that high EST and different egg positions affected embryonic mortality and hatchability of fertile eggs. In eggs with higher EST, higher (P<0.05) mid and late stage embryo mortality rates and consequently, lower (P<0.05) hatchability of fertile eggs were found in comparison to other groups. Similarly, the eggs placed in the top trays had higher (P<0.05) late stage embryo mortality than the ones in the bottom trays. This is thought to be due to high EST. However, there was no significant (P>0.05) difference in embryonic mortality and hatchabilty of fertile eggs according to egg weights. High EST (100.5 degrees F, 101.0 degrees F, 101.5 degrees F and 102 degrees F) increases the embryonic mortality especially in the last period and consequently decreases hatchability of fertile eggs. As EST increases, it can have even more detrimental effects depending of the position of the egg in the incubator.