First Evaluation of Infrared Thermography as a Tool for the Monitoring of Udder Health Status in Farms of Dairy Cows

Abstract

The aim of the present study was to test infrared thermography (IRT), under field conditions, as a possible tool for the evaluation of cow udder health status. Thermographic images (n. 310) from different farms (n. 3) were collected and evaluated using a dedicated software application to calculate automatically and in a standardized way, thermographic indices of each udder. Results obtained have confirmed a significant relationship between udder surface skin temperature (USST) and classes of somatic cell count in collected milk samples. Sensitivity and specificity in the classification of udder health were: 78.6% and 77.9%, respectively, considering a level of somatic cell count (SCC) of 200,000 cells/mL as a threshold to classify a subclinical mastitis or 71.4% and 71.6%, respectively when a threshold of 400,000 cells/mL was adopted. Even though the sensitivity and specificity were lower than in other published papers dealing with non-automated analysis of IRT images, they were considered acceptable as a first field application of this new and developing technology. Future research will permit further improvements in the use of IRT, at farm level. Such improvements could be attained through further image processing and enhancement, and the application of indicators developed and tested in the present study with the purpose of developing a monitoring system for the automatic and early detection of mastitis in individual animals on commercial farms.

Keywords: dairy cow; imaging analysis; infrared thermography; mastitis detection; udder health status.

Figure 1

The figure shows some image elaborations performed by the algorithm of the developed software application. In details, in (A) is reported an example of a thermographic image acquired during the study carried out; In (B) is shown the result obtained applying as thresholds, a range of intensities calculated through the above reported formulas ([1,2]) and after identifying in thermographic image the pixel with the maximum intensity value (PI_max). In the figure, almost the whole cow udder is highlighted. As a consequence, a grid, of dimensions 4 × 4 pixels can be applied in order to calculate the surface distribution of temperatures. In a following step, the maximum value of udder skin temperature (T_max) can be identified as the maximum value within the surface temperatures calculated; In (C), it is shown with a red cross the location of the pixel PI_max and with a green contour the AP_T calculated; In (D), finally, is reported the “temperatures proximity area” (AP_T) obtained considering the coordinates of PI_max and a set of connected pixels which intensities are different from zero after applying the above reported filter [3].

Figure 2

Receiver operating characteristic (ROC) curve of the statistical test built evaluating the variable T_max and different possible cutoff levels. For the determination of udder health status, an SCC’ threshold of 200,000 cells/mL was used. The ROC curve was obtained through the procedures “prediction” and “performance”, package “ROCR” of the “R” statistical software tool.

Figure 3

ROC curve of the statistical test built evaluating the variable T_max and different possible cutoff levels. For the determination of udder health status, an SCC’ threshold of 400,000 cells/mL was used. The ROC curve was obtained through the procedures “prediction” and “performance”, package “ROCR” of the “R” statistical software tool.