Experiments were conducted to evaluate the effect of formaldehyde fumigation in an operating incubator on bacteria contaminating the egg shell surface and on the hatchability.
Egg shells were contaminated with Staphylococcus aureus artificially and the shells were set in an operating incubator. Formaldehyde was liberated from 40ml of formalin mixed with 20g of potassium permanganate per 1m3 of the incubator capacity. The fumigation period was 0.5, 1 or 3 hours. Results on the number of bacteria on the egg shell surface after the fumigation and the number of egg shells on which survived bacteria were detected indicate that a better effect of disinfection is obtained by the 1-hour fumigation than by 0.5-hour fumigation. Even after 3-hour fumigation, surviving bacteria were detected. When the egg shells were heavily contaminated with bacteria, satisfactory disinfection was not obtained.
The hatching eggs were fumigated with formaldehyde prior to incubation and divided into 2 groups as treated and control groups. The eggs were set in the incubator 7 times successively with 7-day intervals. After setting the eggs when the temperature in the incubator regained a normal operating level, formaldehyde was released. Concentration of formaldehyde was the same as above and fumigation was carried out for 1 hour. Vents of the incubator were closed during the fumigation period. The eggs in the treated group were fumigated 3 times in the setter and once in the hatcher. Hatchability of the eggs in the treated group which were stored for 3 to 10 days prior to the incubation was not different from that of the eggs in the control group stored for the same period. Hatchability of the treated eggs stored for 11 to 16 days was lower than that of the eggs in the control eggs stored for the same period and that of the treated eggs stored for 3 to 10 days. Statistically significant differences were not observed in the body weight between the chicks hatched from the eggs in 2 groups and also in the mortality up to 4 weeks of age.