92 INCUBATION 



MANAGEMENT OF INCUBATORS 



Incubators are managed so as to duplicate as nearly 

 as possible the conditions existing under the hen in 

 natural incubation. Heat, moisture, and ventilation are 

 the main factors to watch. 



Temperatures Necessary for Incubation. When fertile 

 eggs are exposed to a temperature of 100 F., or a 

 little higher, the germ cell begins to grow; if this 

 degree of heat is long continued the formation of a 

 definite embryo follows, from which, in the case of hen's 

 eggs kept constantly in a uniform temperature of 103 F. 

 for 21 da., living chicks result. The temperature under 

 sitting hens varies from 95 F. to 105 F. The most 

 satisfactory results are obtained from a temperature 

 ranging from 102 F. to 103 F. The average tempera- 

 ture at the lower side where the egg rests in the nest 

 is about 98 F.; at the center of the egg it is about 

 101 F., although at the surface or top of the egg the 

 temperature registers about 103 F. Eggs hatch best in 

 an incubator at a temperature of 103 F., but they hatch 

 fairly well in a temperature that varies from 101 F. 

 to 103 l / 2 F. ; and they may hatch if the temperature 

 goes as low as 99 F. and as high as 106 F. Under the 

 influence of low or irregular temperature, the hatch 

 is delayed and the number of chicks obtained is a 

 matter of uncertainty. 



The heat under sitting hens varies fully as much as 

 is permissible .with incubators. A regular temperature 

 that does not go below 102 F., nor above 103 F., is 

 normal for the incubation period, except at the time of 

 turning or cooling of the eggs. If the heat goes below 

 normal, the hatch is delayed; if it goes above normal, 

 the hatch is hastened; as a consequence of either of 

 these conditions the eggs may be destroyed. 



A regulator, or thermostat, is used to control the 

 temperature in the egg chamber of an incubator. This 

 is properly adjusted before eggs are placed in the 

 machine. 



