The dominant picture provided by the results of this study is that the responsiveness of dairy cattle (both cows and calves) to challenge is mediated by multiple traits, i.e., is multidimensional.Applying principal component analysis (PCA) to behavioural and physiological response measures always yielded at least two components (dimensions) without cross-loading of variables, even when it was widely assumed that those measures could be related to the same trait.This seems to contrast with prevailing concepts of individual differences which emphasized the existence of major unifying dimensions such as, for example, fearfulness (Boissy, 1995, Jones, 1996), temperament (Clarke and Boinski, 1995), behavioural syndrome (Sih et al., 2004a, b) or coping style (Koolhaas et al., 1999, see Korte et al., 2005 for a related characteristic defining the unidimensional distinction between “hawk” and “dove” type personalities in animals and men).
However, from many reports in the literature, covering many species, it appears that multidimensional response patterns to stressors seem to be the rule rather than the exception.
For example, multiple independent characteristics were obtained after correlational analyses, including PCA, of behavioural and physiological measures of response to challenge in sunfish (Coleman and Wilson, 1998), geese (Kralj-Fiser et al., 2006), quail (Mignon-Grasteau et al., 2003; Miller et al., 2006), deer (Pollard et al., 1994; Bergvall et al., 2011), laboratory rodents (Kanari et al., 2005; Ibanez et al., 2007, 2009), dogs (Svartberg, 2005), pigs (Forkman et al., 1995; Spoolder et al., 1996; Mendl et al., 1998; D’Eath and Burn, 2002; Janczak et al., 2003a, b; Van Erp – van der Kooij et al., 2002; Brown et al., 2009), and cattle (Piovezan et al., 1998; Kilgour et al., 2006; Petherick et al., 2009a).
Clearly, there is a need for alternative interpretations of individual differences that go beyond univariate classifications.
Welfare of laying hens under free range production.
Development of feather pecking behaviour by free range laying hens.
Evaluation of non-confinment housing systems for farrowing / lactating sows.The application of remote sensing technology to monitor extensively managed livestock.The main aim of the work described in the present thesis was to examine the consistency of individual differences in behavioural and physiological responses to acute stressors in dairy cattle in a longitudinal fashion, i.e. Information about the variation in the reactivity of dairy cattle to a “real-life” challenge was provided by a study of heifers’ responses to first-time machine milking.A pharmacological validation experiment helped to interpret the response patterns that calves exhibited in behavioural tests designed to induce stress.The long-term longitudinal study enabled clarification of the relationship between responses of heifers to first machine milking and their earlier responses to behavioural tests.In this general discussion, I will consider the results in a wider context, and also specifically focus on (i) the multidimensional nature of response patterns to stress, (ii) the significance of individual differences in stress responsiveness in (farm) animals, and (iii) some practical implications of the findings of this thesis.