Infrared thermography as an alternative technique for measuring body temperature in cattle1

Objective: The objective of the current experiment was to evaluate the use of infrared thermography (INFRA) as an alternative to rectal temperature (RT) for monitoring body temperature in steers. Materials and Methods: An Escherichia coli lipo- polysaccharide (LPS) was administered to 31 steers (initial BW 295.8 ± 46.5 kg) via i.v. injection to produce a febrile response. Each steer was fitted with an indwelling rectal probe to monitor changes in RT in 30-min intervals. Thermal temperatures (INFRA) were collected in 30-min increments beginning at h 0.5 to 1.5, h 2.5 to 3.5, and h 4.5 to 5.5. Additionally, temperatures were collected in 60-min increments beginning at h −1.5 to −0.5 and h 6.5 to 12.5. Relative to LPS administration, thermal temperatures were subsequently recorded at h 18.5, 24.5, 36.5, and 47.5. Correlation analyses were conducted using PROC CORR where Pearson and Spearman correlation coefficients were evaluated between the RT and INFRA. Additionally, RT and INFRA were analyzed using PROC MIXED where the model included temperature measure- ment method (RT or INFRA), hour, and the interaction of method × hour. Steer within temperature measurement method was included as a random effect and was the sub- ject of the repeated measures analysis. Results and Discussion: Increases in RT and INFRA were evident within 1 h of the LPS administration, both methods confirming an induced febrile response. Rectal temperature and INFRA did not differ for 50% of the time points (P ≥ 0.16); however, the 2 methods differed at h −0.5, 0.5, 1.5, 5.5, 9.5, 10.5, 11.5, 18.5, 24.5, 36.5, and 47.5 (P < 0.01). Temperatures between each method diverged 9.5 h after LPS was given. A Pearson correlation of 0.71 (P < 0.01) was noted between RT and temperature of the eye measured using INFRA. Likewise, a Spearman correla- tion of 0.66 (P < 0.01) was noted between RT and INFRA measurements. Infrared imaging is noninvasive, quick to perform, and decreases additional stressors caused by han- dling and restraint of the animal. Implications and Applications: These data suggest that further research is necessary for INFRA to be a viable alternative to RT measurements in cattle.