Evaluating the relationship between infrared thermography and somatic cell count in healthy lactating ewes

Infrared thermography (IRT) is a rapid, real-time, and non-invasive technique that measures surface temperature by detecting infrared radiation emitted by body tissues. Its use has been increasingly investigated as a diagnostic tool for assessing udder inflammation. The objective of this study was to evaluate the relationship between mammary surface thermal response and milk somatic cell count (SCC) in healthy lactating ewes. The study involved 44 healthy lactating ewes (88 udder-halves). A preliminary SCC sampling was performed to select animals covering a wide range of SCC values. Udder infrared thermal images were acquired using a FLIR T650sc camera before milking, concurrently with the collection of individual udder-half milk samples for SCC determination. SCC from the second sampling, collected immediately after thermographic image acquisition, were used to evaluate the relationship with minimum (TMIN), mean (TMEAN), and maximum (TMAX) udder surface temperatures. SCC values were screened for outliers, and 15 udder-halves were excluded. Consequently, 73 udder-halves were retrospectively classified according to SCC as follow: low (<69,000 cells/mL), medium (69,000-163,000 cells/mL), high (163,000-384,000 cells/mL), and highest (>384,000 cells/mL). General linear mixed model (GLIMMIX) and Pearson correlation were performed. As expected, SCC differed among groups (p < 0.001). However, SCC classes did not influence minimum (p = 0.06), mean (p = 0.60) or maximum (p = 0.85) udder temperature. No correlations were found between SCC and TMIN (r = -0.014), TMEAN (r = 0.005), or TMAX (r = 0.045). Under the conditions of the present study, mammary IRT alone was not associated with variations in milk SCC in healthy lactating ewes.