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Energy and Gaseous Metabolism of the Chicken from Hatch to Maturity as Affected by Temperature

Four Figures

Animal Husbandry Division, Bureau of Animal Industry, U. S. Department of Agriculture, National Agricultural Research Center, Beltsville, Maryland

The energy and gaseous metabolism of Rhode Island Red female chickens, averaging 4 days, 2 weeks, 5 weeks, 8 weeks, 12 weeks, 18 weeks, 23 weeks and 1 year old, were determined by use of one of the respiration calorimeters in the calorimetry laboratory of the Bureau of Animal Industry, Agricultural Research Center, Beltsville, Maryland. The instrument is similar to the one described by Barott ('37). More than 500 1-day experiments were made.

Results were obtained with environmental temperatures at approximately 5°F. intervals in the range from 20° to 103°F. Conditions other than temperature were: Relative humidity 50–60%, 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. The results define the metabolic rate of each age of chicken studied, at each environmental temperature investigated. A point of flexure occurs at the temperature where metabolism is a minimum. This minimum occurs at 95°F. for baby chicks and chickens 2 weeks old. As the chicken gets older the minimum occurs at a temperature which is progressively lower until for 1-year-old hens, the minimum occurs at approximately 70°F. The maximum metabolism occurs at the lowest temperature the chicken could survive. This temperature has not yet been determined for chickens older than 8 weeks.

The data obtained for each 24-hour period show the typical diurnal rhythm in the metabolism of the chicken, with a maximum value at 8 A.M. and a minimum value at 8 P. M.

The amounts of protein, fat and carbohydrate metabolized by the chickens were computed. The amounts of the three food constituents metabolized were: protein, 69%; fat, 27% and carbohydrate, 4%.

The observed R.Q. approximates 0.717 at all ages and all temperatures. The observed oxygen T.Q. is 3.11 and the observed carbon dioxide T.Q. is 3.16.

The water of respiration is fairly constant at temperatures below that where minimum metabolism occurs. Above this temperature there is an enormous increase due to the large amount of water exhaled for cooling at the higher temperatures.