Body Temperature as a Remote Measure of Health in Sheep

Abstract

The measurement of body temperature in sheep has been a well investigated topic, providing insights into the health and physiological state of animals. Many common illnesses and disease are associated with a change in body temperature. The ability to extend this measurement into extensive production systems would be of benefit to producers, researchers and anyone interested in the health of their animals. The aim of this thesis was to identify common health issues and indicators, explore one of the most suitable indicators in terms of its applicability to animal health measurement, and investigate the available technologies which may be of use in remote monitoring of sheep health.<br/> The Chapter 2 literature review section of this thesis has presented an overview of the current knowledge regarding health measurement in sheep, focusing on temperature measurement as a useful indicator of common health issues experienced by sheep in extensive production systems. It then explores the currently available technologies with which remote temperature measurement may be possible.<br/> Chapter 3 aimed to investigate how well body temperature measured at peripheral sites in the neck muscle (Tn) and tail subcutaneous measure (Tt) reflected core (vaginal) temperature (Tv) detection and the daily rhythmicity in the body temperature of sheep. The impact of feeding frequency on both core and peripheral temperature measures was also investigated. While absolute and fitted temperature parameters differed between Tv, Tn and Tt, pattern similarities were observed at time points across the measurement day, with Tv, Tn and Tt exhibiting similar rhythmicity per the time of day. Additionally, feeding schedule may impact on short term fluctuations over the day in body temperature, but not on overall rhythmicity and temperature range.<br/> Chapter 4 aimed to investigate the similarities between core and two peripheral sites when measuring temperature changes of sheep under a fever challenge. Significant differences were observed between challenge and baseline cosinor adjusted data for all parameters for Tv, and most for Tn while, for the purposes of fever detection or detection of clinically significant temperature change, subcutaneous Tt measurements showed minimal detection of treatment effect (P < 0.05).<br/> In Chapter 5 an initial investigation and then a main experiment were conducted to investigate the potential for infrared thermography (IRT) to detect skin inflammation in sheep, particularly with regards to inflammation associated with fly strike. In the main experiment, significant differences were found between control and sites injected with vaccine formulation (Covexin©10) for most of the experimental period for the short wool length, while fewer significant differences were found between injection and control sites for medium wool and long wool lengths (P < 0.05). Variation was lower across the measurements for short wool compared to medium and long wool. These findings suggest that IRT may have application in the detection of skin inflammation in sheep at short wool lengths, and may have limited application at longer wool lengths.<br/> The experiments undertaken as part of this thesis have identified and demonstrated the capabilities and limitations of temperature sensing microchips and infrared thermography and informed as to their possible applications for remote temperature monitoring in sheep.