The effect of air movement, air temperature and infrared radiation on the energy requirements of sheep

Abstract

Responses of VO2 of sheep to changes in air velocity were virtually complete 50 min after exposure, responses to changes in air T° 30 min after exposure and responses to changes in i.r. radiation 50-60 min after exposure. Responses of skin T° of the trunk to changes in air velocity were very rapid. They were also rapid for changes in air T°, but with changes of i.r. radiation intensity, although initially the responses were rapid, subsequently they were slow. In all experiments the response of the skin T° of the foot to changes in climate were slower than that of the trunk, being completed in periods of time similar to those noted for VO2. Wind of 4.2 mph at -3° increased VO2 3.3 times relative to thermoneutral zone. Rectal T° increased with wind velocity. Tissue insulation of the sheep once vasoconstriction had occurred was unaffected by wind velocity or by environmental T°. External insulation (joint insulation of the air interface and the coat) increased linearly with fleece length over the range 5-50 mm. External insulation fell with increasing wind velocity.