Mar., 1938] Electric Brooding of Chicks, II. Heat Requirements 29 



Curtain Crowding — The chicks frequently crowded through the cur- 

 tain many times showing extended wings and open beaks. Overheat- 

 ing and/or a need of fresh air are the obvious causes of such action. 

 Intestinal and Lung Conditions — As stated previously all chicks dying 

 during these experiments have been subject to post mortem examina- 

 tion by the Poultry Pathology Laboratory. The same condition has 

 consistently prevailed during the several years ' work ; the great ma- 

 jority of deaths have shown congestion of the lungs, indicating pneu- 

 monia, and digestive disorders. At least one of these conditions was 

 always in evidence upon autopsy. The average mortality by years has 

 been as follows: 1933, 10.25% ; 1934, 14.8% ; 1935, 2.47% ; 1936, 3.7% 

 (fourteen weeks). 



The presence of pneumonia would seem to indicate a lack of heat or 

 a period of excessive heat followed by chilling. The coincidence of 

 digestive disturbance should be noted. 



Tests of the temperature regulation throughout the brooders showed 

 a considerable variation in both a vertical and horizontal direction, most 

 important of which were what seemed to be deficiencies in heat near the 

 floor (vertical) and near the curtains (horizontal). 



A study of these five factors (most significant of which were the 

 digestive and lung conditions) with respect to the heat regulations, 

 particularly in the vertical direction, led to the development of the fol- 

 lowing hypothesis as being a major cause of mortality. 



The lowes.t temperatures and most drafts occurred near the floor 

 of the brooder especially when the chicks' bodies blanketed off the heat 

 from above. As a result of this condition, chilling of the digestive 

 tract (located on the underside of the body) developed. Until stop- 

 page occurred, no evidence of the chicks' condition would be noticed. 

 During this period, however, a lowering of the vitality and strength of 

 the individual was undoubtedly taking place. 



At the same time the temperatures of the upper levels of air — at or 

 just above the chicks' backs (location of the lungs)— usually were the 

 highest, even to the point of being excessive. 



If continued heat were abnormally high, weakness might develop in 

 the digestive organs or, as an alternative result, chilling after over- 

 heating would be likely. Hence, the bird would appear to die of pneu- 

 monia whereas the probable primary cause is a digestive disorder pos- 

 sibly related to the temperature to which the digestive tract was exposed. 



The work herein described and conducted during the past two years 

 has had as a basis this hypothesis. Being set up as an engineering and 

 poultry husbandry project, the objective has been to determine through 

 the practical use of commercially manufactured electric brooders the 

 proper operating temperatures, distribution of heat, protection from 

 outside influences, etc., which would provide the greatest efficiency in 

 operation and, at the same time, develop the proper environment for 

 rearing chicks to the highest degree of physical condition. 



Note: The work of M. Kleiber and J. E. Daugherty (published in the 

 Journal of General Physiology, May 20, 1934, under the title "The Influence of 

 Environmental Temperature on the Utilization of Food Energy in Baby 

 Chicks") verifies to a remarkable degree the conclusions drawn from the ex- 

 periments at this Station. A careful analysis of their report will well re- 

 ward anyone who wishes to make a further study of brooding conditions. 



