This research was carried out at the poultry farm of the Agriculture High Institute (Gitega), . University of Burundi. Giteg-Burundihas an altitude of 1680 m over sea level. A total of 8717 eggs from egg-production strain "Sasso" imported
Importede from France to be introduced in Burundi were incubated in 19 batches in two seasons (rain and dry season). They were incubated as 12 batches in rain season (December-May) with a total of 5830 eggs and 7 batches in dry season (July-August) with a total of 2887 eggs. The results showed that there was no significant effect of seasons on fertility percentage under the high altitude environment at Gitega-Burundi. The hatchability of fertile eggs had low percentage than that known at sea level. No significant difference was detected between seasons for hatchability of fertile eggs. The reduced percentage of hatchability and high percentage of embryonic mortalities under the high altitude environment of Gitega may be due to oxygen hypoxia. The embryonic mortalities showed an increase as the incubation period progressed. There were significant differences between the two seasons for the second period of the embryonic mortality. The highly embryonic mortality was noticed at the last three days of incubation and the embryonic mortality increased as the embryos growth developed. There was a negative significant correlation between fertility and the first period of embryonic mortality and there were negative and highly significant correlations between hatchability of the fertile eggs and the three periods of mortalities. From this work it may be recommended that, to improve the hatchability percentage and to reduce the embryonic mortality, by specific additional ventillation system to
increase the oxygeninjection in the moderne incubators under Gitega-Burundi environment.