Use of infrared thermography to detect inflammation caused by contaminated growth promotant ear implants in cattle.

OBJECTIVE: To compare the infrared thermographic appearance of bovine ears that had received contaminated growth promotant implants with ears that had received clean implants and ears without implants. DESIGN: Prospective study. ANIMALS: 32 yearling crossbred beef steers with a mean weight of 322 kg (708 lbs). PROCEDURE: Contaminated (n = 16) and clean (16) implants were placed in the ears of feedlot cattle. Nonimplanted (n = 32) ears served as a within-animal control for thermographic comparisons. Images of rostral and caudal surfaces were obtained during a 21-day period, using an infrared thermal imaging radiometer. Repeated measures ANOVA was used to determine the relationship between mean temperature in a zone on the rostral surface of the ear and at 3 locations (proximal, middle, distal) on the caudal surface of the ear (response variables) with treatment (ears with contaminated implants or clean implants vs control ears with no implants), time (repeated day of measurement), and interactions among these variables. RESULTS: Significant temperature differences existed between ears with contaminated implants and control ears. Temperatures for ears with clean implants were significantly higher than control ears on day 2. At low ambient temperatures when the ears became wet, a greater temperature contrast was detected between ears with contaminated implants and control ears. CONCLUSIONS AND CLINICAL RELEVANCE: Thermal imaging of the ears of feedlot cattle is a noninvasive diagnostic tool that can be used to identify cattle with abscesses caused by contaminated growth-promotant implants.