282 INCUBATION AND BROODING 



hatched chicks can be cared for Just as easily as five 

 broods of hen-hatched chicks. 



When incubators are used the directions furnished with 

 the machine for its operation should be closely followed. 



Selecting Eggs for Incubation. — Although eggs that 

 are not uniform in size, shape, or thickness of shell ap- 

 parently hatch as well as more nearly perfect eggs, pro- 

 vided all of a kind are put into the same machine, it is in- 

 advisable to use them. The unsafe feature of promiscuous 

 selection lies in the fact that the eggs of poor shape and 

 shell have been laid by hens with whom the char- 

 acteristic of producing eggs of this nature is dominant ; and 

 so the chicks hatched from these eggs show a tendency to 

 lay eggs of poor shape. Then, too, eggs of different sizes 

 and different thicknesses of shell do not respond to the 

 heat of incubation so evenly as do eggs that are more nearly 

 uniform in size and shell. 



It is advisable but not necessary to test out infertile 

 eggs after the sixth or eighth day. It is advisable because 

 removing them obviates crowding at hatching time. 



Effect of Chilling on Incubation. — Eggs should not be 

 used for incubation after a sudden drop in temperature. 

 Where thousands of eggs have been incubated, it has been 

 observed that those collected on the day of a sudden 

 change in temperature, or a day or so afterward, do not 

 hatch so well, even when they have not been chilled, as 

 those collected during the period when the temperature 

 was more nearly uniform, regardless of the degree of cold- 

 ness. It is inadvisable to hold eggs which are to be incu- 

 bated, for any length of time. The only time when it is 

 advisable is when the flock is extremely small and the 

 incubating facilities are Umited. 



