Effects of egg location on the cardboard tray after collection on hatchability of broiler hatching eggs.

Temperature after oviposition has been found to have a considerable influence on the rate of embryonic development and success of the hatching egg storage. General recommendations for egg cooling after oviposition is that eggs should be cooled to below physiological zero level within four to eight hours. The rate at which eggs cool is dependent upon a number of factors such as egg size, initial egg temperature, nest and/or storage area conditions and holding time, air movement, collection material, time spent in the cooler. The objectives of this study were to determine the effects of following factors under different egg cooling pattern in a commercial hatchery on hatchability of broiler breeder eggs; 1) flock age (Young-Old flocks), 2) season (Winter-Summer), 3) egg location on the cardboard egg tray after collection (Inner-Outer). Four experiments were completed to compare the effects of egg location on the cardboard tray after collection. Commercial flocks of Ross 308 broiler breeder were used as the source of broiler hatching eggs. Breeder flock ages were 27 wk (young) and 61 wk (old) in winter and 27 wk (young) and 51 wk (old) in summer season. A total of 2600, 4800, 2600, and 8000 eggs were used in experiment 1, 2, 3, and 4, respectively. All eggs were had been laid within a 15-min period were collected and placed in cardboard egg trays. Eggshell temperature was measured with an infrared thermometer at 30-min intervals during the cooling process. The eggs were divided into two groups, which were inner and outer of the cardboard egg tray and the eggs were marked permanently. All eggs were stored for 5 d at 16°C and 75% RH. At the time of removal of chicks from hatchers (510 h), all unhatched eggs were opened and examined macroscopically to determine, infertile, early, mid, and late embryonic mortality. The cooling pattern has been affected by location of egg after collection in all experiments, but the effects of egg location on hatchability and embryonic mortalities have been changed by the season and flock age factors. For young flocks, the outer located eggs had a significantly lower hatchability when compared to inner side eggs in winter conditions due to significantly higher late embryonic mortality (P < 0.05), whereas in summer season, there was no significant difference between two located eggs (P > 0.05). For old flocks, the outer located eggs had a significantly higher hatchability when compared to inner side eggs in summer conditions due to significantly lower early embryonic mortality (P < 0.05), whereas in winter season, there was no significant difference between two located eggs (P > 0.05). Conclusions: These results suggest that the egg cooling pattern after lay is an important factor to achieve better hatchability and the cooling pattern might be needed consideration as so flock age and season in case the eggs have been collected to cardboard tray. [ABSTRACT FROM AUTHOR]