Energy and Gaseous Metabolism of the Hen as Affected by Temperature

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Abstract
The energy and gaseous metabolism of Rhode Island Red hens between 10 and 13 months of age were determined by use of one of the respiration calorimeters in the calorimetry section of the Bureau of Animal Industry, Beltsville Research Center, Beltsville, Maryland. The instrument is similar to the one described briefly by Barott ('37). Results were obtained at nineteen environmental temperatures in the range from 50° to 95° F. Conditions other than temperature were relative humidity 60%, oxygen content 21%, and carbon dioxide content less than 1%. The oxygen consumption was measured for each 2-hour period, and the heat, water, and carbon dioxide elimination for each 4-hour period. From the above data the respiratory quotient and the oxygen and carbon dioxide thermal quotients were computed. The data obtained during each 24-hour period show the typical diurnal rhythm in the metabolism of the hen with a maximum value in the morning and a minimum in the evening. The results clearly define the metabolic rate of the Rhode Island Red hen for the temperature range studied. A point of flexure occurs at 78°F. This is the temperature of minimum metabolism of the hen. The maximum metabolism occurs at 61° F., at which temperature there is also a point of flexure. The phenomenon of a decrease in metabolic rate between 60° and 50° F. should be investigated to ascertain the reason for the decrease instead of the expected increase in metabolic rate with decrease in temperature. The respiratory quotient was 0.702 ± 0.002. The oxygen and carbon dioxide thermal quotients were 3.25 ± 0.05 and 3.37 ± 0.05, respectively, indicating a fat metabolism. This is consistent with the fact that the data were obtained approximately 20 hours after feeding. The rate of elimination of respiratory water was approximately constant between 65° and 75° F. The rate decreased considerably between 60° and 50° F. but the most striking change occurred between 80° and 90° F. The rate at 90° F. was three times that at 80° F. This was due to the large amount of air inhaled and exhaled for cooling at the high temperature.