Environmental temperature, energy metabolism and heat regulation in sheep. I. Energy metabolism in closely clipped sheep

Abstract

1. The energy exchange of two sheep closely clipped at weekly intervals was determined at three feeding levels and seven environmental temperatures, using a respiration apparatus in which radiant temperature was equal to ambient temperature. All measurements were made under conditions in which the animal was in equilibrium with its environment and heat storage was zero.2. Body weight and fleece growth were both markedly reduced at the lowest feeding level. Weight losses were most marked at the lowest temperatures.3. The energy lost in faeces decreased slightly as environmental temperature increased from 8 to 38° C. Urine energy losses also fell. Losses of energy as methane were maximal in the temperature range 23–28° C. As a result of these changes, the metabolizable energy of food increased with environmental temperature by 7 Cal./24 hr./° C.4. The environmental temperature of the sheep at which their heat production was minimal, i.e. the ‘critical’ temperature was 39–40° C. for the lowest feeding level, 33° C. for the medium feeding level and 24–27° C. for the highest feeding level.