10 



N. H. Agricultural Experiment Station [Bulletin 303 



haust area, square feet of brooder floor area, cubic feet of brooder com- 

 partment and exhaust area per chick. This divergence of practice in 

 manufacture together with the fact that some brooders are used for 

 both natural up-draft and down-draft power ventilation without other 

 change than the addition of a ventilating fan, indicates that definite 

 ventilating rates have not been determined up to this time. It is im- 

 portant to establish values for this air exchange. 



Under-Brooder Heat Measurements 



Temperature readings were taken in January, 1935, with thermo- 

 couples under Brooder No. 2 and Brooder No. 3, each with 250 chick 

 loads, to determine the heat distribution, under colony house conditions. 



The temperature readings were taken at 4" intervals horizontally 

 and V intervals vertically (from I/2" to 3I/2" above floor). The tem- 

 peratures secured were plotted on the diagram (Fig. 4) at points cor- 

 responding to the position at which they were taken under the hover. 

 The lines were then drawn to connect points of equal temperature, 

 (isotherms) 



Case 1 with 3-weeks old chicks showed a generally flat temperature 

 zone but a definite tendency to lose regulation at the lower edge of the 

 curtain. All temperature contours had a tendency to lift at the edge, 



Table III. Brooder Ventilation Factors, 19SA-35. 



Factors 



Brooder 

 No. 1 



Brooder 

 No. 2 



Brooder 

 No. 3 



Square inches of exhaust open- 

 ing per square foot of brooder 

 floor area. 



.415 



.188 



.331 



Square inches of exhaust open- 

 ing per cubic foot of brooder 

 content. 



.65 



.277 



.462 



Number of chicks per square 

 inch of exhaust. 35 



71 



45.5 



