Comparison of infrared, electronic digital and mercury-in glass thermometers: 1. West African dwarf goats

Abstract

Monitoring body temperature accurately is essential in livestock production. Data of body temperature measurements taken concurrently with electronic digital (ED), mercury-in-glass (MG) and infrared (IR) thermometers in 107 (male=38 and female=69) West African Dwarf (WAD) goats aged between 6 months and 3 years were compared to assess the accuracy. ED and MG thermometry was taken via the rectum (TEMPd and TEMPa respectively) while the IR thermometer was used on the opening of the rectum (TEMPiR) and forehead (TEMPiH). The data were subjected to analysis of variance and Pearson correlation analysis. Scatter diagrams were plotted to generate R-squared for the relationships between the readings of the thermometers. Thermometer type had significant (P<0.001) effect on body temperature (BT) in WAD goats. The BT recorded was in the order: TEMPd > TEMPa > TEMPiR > TEMPiH. There was strong positive significant (P<0.001) correlation between TEMPd and TEMPa (r=0.896). The correlations between TEMPd and TEMPiR (r=0.237) and TEMPa and TEMPiR (r=0.222), though significant (P<0.05), were weak. TEMPiH and TEMPiR had positive and significant (P<0.001) correlation (r=0.503). TEMPiH had no significant (P>0.05) correlation with TEMPd and TEMPa. Linear regression of TEMPd with TEMPa, TEMPiR and TEMPiH yielded R² of 0.802, 0.056 and 0.00006 respectively. Deviations from TEMPd obtained were 0.34, 0.92 and 2.54^oC for TEMPa, TEMPiR and TEMPiH respectively. Taking body temperature of WAD goats with IR thermometer on the forehead may not give correct measurement as with the traditional MG and ED thermometers. Temperature measurement with IR thermometer on the opening of the rectum of WAD goats seems to be more accurate than on the forehead.

Keywords: rectal temperature, heat stress, health, welfare, diagnosis