Peripheral regulation of stress and fear responses in pigs from tail-biting pens

Manja Zupan,Adroaldo José Zanella

doi:10.1590/s1806-92902017000100006

Abstract

This study focused on stress physiology by characterizing cortisol responses to stressors in tail biters (n = 10), victims (n = 10), and control pigs (n = 10) of two different breeds (Landrace × Yorkshire, LY; Landrace/Yorkshire × Landrace/Duroc; LYLD) and sexes (females and castrated males). We exposed pigs to 10 min of isolation with a human at the farm and transported them to a controlled environment. There, the behaviour was registered for 10 min during sessions when subjected to a novel object test and to a novel arena test. Sampling times of salivary cortisol were in all the fear tests before testing and 60 min thereafter, while for transportation as well 120 min after the beginning of transportation. We additionally measured cortisol at 7:00 and 16:00 h during three days following transportation. The basal stress axis activity followed a distinct diurnal rhythm between sexes and breeds, with castrated males having higher cortisol level than females and LY pigs higher than LYLD pigs. Following isolation at the farm and transportation, the concentration of salivary cortisol was higher in LY than in LYLD pigs. Pigs considered the exposure to a novel arena, but not to a novel object, stressful by showing a cortisol level after testing higher than before testing. The results suggest a genotypic effect on sensitivity to stress in pigs that have performed tail biting, have been victimized, or have not been involved in tail biting.

Highlights

Tail biting in pigs is a behavioural disorder characterized by oral manipulation of the tail of another pig, often resulting in lesions (Taylor et al, 2010)
In the human test and for the stressor transportation, the results revealed the effect of breed and time
With the significant effect of breed, we found higher cortisol responses in Landrace × Yorkshire (LY) pigs than in Landrace/Yorkshire × Landrace/Duroc (LYLD) pigs

Summary

Introduction

Tail biting in pigs is a behavioural disorder characterized by oral manipulation of the tail of another pig, often resulting in lesions (Taylor et al, 2010). Pigs involved in tail biting suffer from inflammatory responses (Heinonen et al, 2010) and fearfulness (Zupan et al, 2012, 2016), having impaired physical and psychological health. It is a general consensus that the autonomic and the endocrine activities mediate the peripheral components of psychological states such as stress or fear and anxiety. Fearfulness, the predisposition to show fear- and anxietyrelated responses to a range of potential and real threats (Forkman et al, 2007), has implications for the ability to cope with specific types of environmental changes and challenges. Fearful pigs may have a predisposition to become more stressed by environmental changes. There is some evidence that individual differences in ability to adjust to environmental challenges may lead to sub optimal development of stress-axis activity after restraint stress or exposure to novelty (Herman et al, 2005; Fries et al, 2005)

Methods

Results

Conclusion