ENVIRONMENTAL-FACTORS AFFECTING MEASUREMENT OF BOVINE SCROTAL SURFACE-TEMPERATURE WITH INFRARED THERMOGRAPHY

The objective was to determine the effect of time of day (diurnal vari ation), interval after feeding, prolonged recumbency, moisture on the scrotum, and ambient temperature on scrotal surface temperature (SST) in bulls as measured by infrared thermography. There was no significan t effect of diurnal Variation on SST. Within 30 min after the start of feeding, SST at the bottom of the testes and average SST increased, a nd slowly declined thereafter. In bulls that were lying down for at le ast 1 h, SST remained relatively constant after rising at an ambient t emperature of 15 degrees C, but increased after rising at ambient temp eratures of 5 and 25 degrees C. Ambient temperature had a large effect on bottom SST, a small effect on top SST and an intermediate effect o n average SST. The SST gradient (difference between top and bottom SST ) was greatest at 5 degrees C and least at 25 degrees C. When ambient temperatures changed rapidly, there was an apparent overcompensation i n SST (measured 3 h after ambient temperature stabilisation), followed by a normalisation of the temperature (measured 24 h after temperatur e stabilisation). Moisture on the scrotum decreased SST and following drying returned to normal in approximately 30 min. Therefore, for repr esentative SST measurement, scrotal infrared thermography can be perfo rmed at any time of the day, but should not be done within several hou rs of feeding or until 1 h after rising, and the scrotum should be dry . Measurement of SST can be conducted over a wide range of ambient tem peratures, although abrupt changes in ambient temperature may result i n artifacts due to overcompensation.