Eye white may indicate emotional state on a frustration-contentedness axis in dairy cows

Research on welfare indicators has focused primarily on indicators of poor welfare, but there is also a need for indicators that can cover the range from good to poor welfare. The aim of this experiment was to compare behaviour elements in dairy cows shown in response to a frustrative situation as well as elements shown as a response to pleasant, desirable stimuli, and in particular measure the visible percentage of white in the eyes. The subjects of the study were 24 randomly selected dairy cows, 12 in each group, all Norwegian Red Cattle. In a 6 min test of hungry cows, access to food and food deprivation were used as positive and frustrating situations, respectively. The cows of the positive stimulus group were fed normally from a rectangular wooden box. When the deprived animals were introduced to the stimulus, the box had a top of Plexiglas with holes so that the cows could both see and smell the food, but were unable to reach it. All cows were habituated to the box before the experiment started. All food-deprived cows showed at least one of these behaviours: aggressiveness (the most frequent), stereotypies, vocalization, and head shaking, while these behaviour patterns were never observed among cows given food. The percentage of white of the total visible eye area was larger than normal in the food-deprived cows, gradually increasing until 4 min after test starts, while it was consistently lower than normal in the cows that were fed. The percentage of white correlated positively with the number of aggressive buts in deprived cows. The results suggest that the eye white may be a dynamic indicator of emotions in dairy cattle on a frustration-contentedness axis. (C) 2002 Elsevier Science B.V. All rights reserved.