Electric Brooding of Chicks 

 II. Heat Requirements 



Preliminary experiments in electric brooding were reported in 

 Station Circular 46. Certain temporary conclusions, then drawn, were 

 briefly as follows: (1) electric brooding is practical and can be carried 

 on under very severe climatic conditions without auxiliary heat or ex- 

 cessive mortality; (2) no significant differences in results were observed 

 in insulated versus non-insulated houses; and (3) little is to be gained 

 by house ventilation for the purpose of lowering the humidity. It was 

 suggested that floor conditions be investigated on the premise that they 

 might be responsible for a constant and pronounced variation in tem- 

 perature throughout the 24-hour period, for degree of chick movement, 

 and for the formation of a moist ring about the brooder. 



1934-35 EXPERIMENTS 



Accordingly, the insulating material on walls and ceiling of the 

 houses used in the previous year's trials was removed. This material 

 was then applied to the floors of the four houses so that varying de- 

 grees of floor insulation values were established. Thus, House 13 was 

 provided with a double wood floor, paper between floors ; House 14, with 

 double wood floor plus one layer 7/16" insulating board enclosed in a 

 sealed tar-paper envelope laid between the floors ; House 15, with sim- 

 ilar construction except for two layers of insulation ; and House 16, with 

 three layers of insulation board. (Fig. 5.) Around the base of each 

 house earth or boarding was placed so as to give wind protection to the 

 floors as uniformly as possible. 



Equipment 



Temperature readings were obtained by installing thermocouples 

 (1) on the under-surface of the sub-flooring and exposed to the air under 

 the house. (2) between each layer of insulation or flooring, and (3) on 

 the finished surface of each floor. 



House 13, having no insulation between floors, and House 16, hav- 

 ing the maximum amount, were provided with observation booths at- 

 tached to the west side. A window 2' x 4' was placed in the wall so that 

 chick movement could be observed without disturbance. The two re- 

 maining houses were fitted with observation windows only. 



The leads from the thermocouples were carried to a connecting 

 panel in each booth or adjacent to the observation window so that read- 

 ings could readily be made with the potentiometer. Recording and 

 check thermometers were employed as in the previous experiments. 



Three standard makes of brooders were used. (See Fig. 1.) 

 Brooder No. 1 was of circular design with a manufacturer's rating of 

 350 chicks. On the flat ceiling section a 440-watt, open-coil heating 

 unit was mounted concentric with the center of the brooder. Natural 



