The effect of environmental temperature on the energy metabolism of cattle

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Abstract
1. A relatively inexpensive closed-circuit respiration chamber for cattle is described. 2. Experiments with two steers are reported in which heat production and energy retention data were measured at different levels of food intake and at different environmental temperatures. 3. The energy lost in faeces increased with improving plane of nutrition but was not significantly affected by the environmental temperature. Urine energy losses fell with increasing environmental temperature at low planes of nutrition. Methane losses increased with improving nutritional plane but were reduced by high environmental temperatures at high levels of food intake. 4. The heat production of fasting animals, or animals on low planes of nutrition was not influenced by the environmental temperature in the range 20–40° C. On higher planes of nutrition an increasing environmental temperature increased the animals' heat production. 5. The major factor determining energy retention in different environments is the heat production of the animal. Net energy values consequently vary with temperature.