Non-invasive measurement of stress in dairy cows using infrared thermography.

The possibility that changes in eye temperature, measured using infrared thermography (IRT), can detect stress in dairy cattle was examined by six different stimulations of the stress axis. Six cows were given six treatments in a random Latin-square design: 1) Control (saline) 2) ACTH (0.05 mg Synacthen) 3) bCRH (20 mug) 4) bCRH (40 mug) 5) epinephrine (1.4 mug /kg liveweight) and 6) social isolation. Treatments were administered at time 0 and blood samples were taken at -30, -15, 0, 5, 10, 15, 20, 30, 40, 50, 60, 75, 90, 120, 180 and 240 min except for epinephrine which was sampled at -30, -15, -10, -5, 0, 2, 5, 10, 15, 20, 30, 45, 60, 90 and 120 min. Core body temperature was recorded every 10 min and eye images collected every 2 min. Eye temperature and cortisol increased following catheterization (P<0.05). ACTH increased following bCRH, cortisol increased following ACTH and bCRH (P<0.001) and NEFA increased following epinephrine (P<0.001). Core body temperature was unaffected by treatments. Eye temperature was unaffected by CRH and epinephrine but was higher 30 and 60 min following control and ACTH (P<0.001). Our results provide evidence that exogenous HPA stimulation does not increase eye temperature. The increases in eye temperature following catheterization however raise the possibility that a cognitive component may be required for an eye temperature response to occur.