ABSTRACT
To compare the effect of eucalyptus extract and formaldehyde gas on the hatchability, survival rate, and microbialload of embryos and biological biomarkers of embryos in the fertile eggs of broiler chicken, 120 fertile eggs weredivided into four groups (each group contained 30 eggs). The studied groups included the first and second groupsin which eucalyptus extract at concentrations of respectively 1.100 and 1.200 was used as a disinfectant, the thirdgroup in which formaldehyde gas was used as a disinfectant and the fourth group as a negative control in whichthe studied eggs were sprayed with distilled sterilized water without using any disinfectant. All eggs were kept ina standard incubation system and the hatching rate was determined after 21 days. The hatched embryos werecultured to identify infection with E. coli. The hatched chickens were monitored for one week, and survival rateand the amount of using grain, overweight, and food conversion ratios were studied in different groups. The resultsshowed that the disinfection of fertile egg with eucalyptus extract at the concentration of 1.200 was similar to thatof formaldehyde, while the eucalyptus extract at the concentration of 1.100 can increase the hatching rate and thegrowth indicators. Therefore, it seems that using eucalyptus extract in the appropriate conditions andconcentrations can be an appropriate alternative for formaldehyde.