Abstract
From the 1990s, extensive research was started on the physiological aspects of individual traits in animals. Previous research has established two extreme (proactive and reactive) coping styles in several animal species, but the means of reactivity with the autonomic nervous system (ANS) activity has not yet been investigated in cattle. The aim of this study was the characterization of cardiac autonomic activity under different conditions in cows with different individual characteristics. For this purpose, we investigated heart rate and ANS-related heart rate variability (HRV) parameters of dairy cows (N = 282) on smaller- and larger-scale farms grouped by (1) temperament and (2) behavioural reactivity to humans (BRH). Animals with high BRH scores were defined as impulsive, while animals with low BRH scores were defined as reserved. Cardiac parameters were calculated for undisturbed lying (baseline) and for milking bouts, the latter with the presence of an unfamiliar person (stressful situation). Sympathetic tone was higher, while vagal activity was lower in temperamental cows than in calm animals during rest both on smaller- and larger-scale farms. During milking, HRV parameters were indicative of a higher sympathetic and a lower vagal activity of temperamental cows as compared to calm ones in farms of both sizes. Basal heart rate did not differ between BRH groups either on smaller- or larger-scale farms. Differences between basal ANS activity of impulsive and reserved cows reflected a higher resting vagal and lower sympathetic activity of reserved animals compared to impulsive ones both on smaller- and larger-scale farms. There was no difference either in heart rate or in HRV parameters between groups during milking neither in smaller- nor in larger-scale farms. These two groupings allowed to draw possible parallels between personality and cardiac autonomic activity during both rest and milking in dairy cows. Heart rate and HRV seem to be useful for characterisation of physiological differences related to temperament and BRH.
Highlights
Knowledge of the behavioural characteristics of dairy cows is important for the breeding, housing and management of animals
Heart rate and LF/high-frequency component (HF) were higher, while root mean square of successive differences (RMSSD) and HF were lower in temperamental cows than in both calm and intermediate animals when measured during lying posture (Table 3)
We found no differences between groups in RMSSD during milking (P > 0.05, regarding all comparisons)
Summary
Knowledge of the behavioural characteristics of dairy cows is important for the breeding, housing and management of animals. Behavioural and physiological differences between individuals in response to a stressor or an environmental challenge are often described with the terms ‘coping style’ [1,2] and ‘temperament’ [3,4]. The first type is the active response, which was originally described by Cannon [12] as the ‘fight or flight’ response. This active response is characterized by territorial control and aggression. Engel and Schmale [13] described the second type of stress response as the conservationwithdrawal response, which is characterized behaviourally by immobility and low levels of aggression. Based on a review on coping styles in animals [10], it is preferable to use the terms proactive coping rather than active coping and reactive rather than passive coping
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