Abstract
The aim of this study was to analyze whether the activity of the autonomic nervous system (ANS) differs between two regrouping procedures in goats, which would indicate stimulus specificity of these stressors. Applying two regrouping procedures, we evaluated heart rate and heart rate variability (RMSSD, SDNN, and RMSSD/SDNN). The two regrouping procedures were (1) introduction of individual goats into established groups (“introduction experiment”) and (2) temporary separation and subsequent reintegration of individuals from/into their group with two levels of contact during separation (“separation experiment”). In the “introduction experiment,” the heart rate of introduced goats while lying decreased continuously from an average 78 to 68 beats/min from before the introduction to the last day of the introduction period. Inversely, RMSSD increased continuously from 41 to 62 ms, which, on its own, would indicate an adaptation to the situation. During the “separation experiment,” heart rate while lying was higher when goats were separated in the “acoustic contact treatment” (82 beats/min on average) compared with the “restricted physical contact treatment” (75 beats/min on average). This difference reflected a higher level of arousal during the “acoustic contact treatment.” However, heart rate activity did not allow detecting effects of separation or reintegration. Even though it can be assumed that both the separation and introduction of goats are stressful for goats, the ANS reactions observed in this study differed between the two management procedures indicating that the ANS activation was specific to each situation. In addition, we discuss the ANS results in context with earlier findings of variables of the hypothalamic pituitary adrenal (HPA) axis (fecal cortisol metabolites) and behavior (lying and feeding). As correspondence between ANS, HPA, and behavioral reactions was limited both within and across experiments, the results of this study underline the concept that stress response patterns are context specific.
Highlights
The physiological stress response is an important variable that can help to assess animal welfare [1, 2]
In the “introduction experiment,” heart rate continuously decreased (Table 3; Figure 1), whereas RMSSD and SDNN continuously increased in the course of the introduction period compared with the reference day (Table 3; Figures 2A,B)
For both RMSSD and SDNN, these were the models with the second highest probability [their probability and evidence ratio being 0.83 and 0.97, respectively, in comparison with the models with the highest probability which to day included presence of horns and rank category (RMSSD) or presence of horns (SDNN) as main effects]
Summary
The physiological stress response is an important variable that can help to assess animal welfare [1, 2]. In the “introduction experiment” (conducted from November 2009 to January 2010), four groups, each consisting of six adult, female, non-lactating goats, were included. Two of these four groups were composed of horned and two of hornless goats. The “separation experiment” was conducted from March to July 2010 utilizing four experimental groups, each consisting of seven horned, adult, female, non-lactating goats. Single fixed effects are no longer significant (or not), but the chosen model as a whole represents the approximation that best explains the observed data This approach of model selection is conceptually different to the classical step-wise backwards testing, as it tests the probability of a specific model given the data [35, 38]. In analogy to a classical frequentist approach, effect sizes of the fixed effects need to be considered to assess biological relevance [38]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
