Evaluation of visible eye white and maximum eye temperature as non-invasive indicators of stress in dairy cows

As expected, sympathetic activity and cortisol concentration were higher in the claw trimming than in the feeding situation. However, neither maximum eye temperature nor percentage of visible eye white differed between treatments. Instead, the results of these measurements differed between the breeds. The maximum eye temperature increased during and after both situations in Brown Swiss cows, whereas in Red Holstein cows, it increased after (but not during) both situations. Furthermore, we found that Red Holstein cows had a lower percentage of visible eye white than Brown Swiss in general. This finding might be due to differences in eye coloration patterns, with Red Holstein cows having more contrast between eye white and iris and Brown Swiss having less contrast because of their darker eye white. This breed effect might have masked potential treatment effects.