Behaviour, heart rate, and heart rate variability in pigs exposed to novelty

Abstract

-In the present study, we investigated behavioural responses and determined parameters of heart rate variability (HRV) to elucidate a relative activation of autonomic nervous system (ANS) during baseline (10 min) and in response to potentially stressful situations (10 min) in two pig breeds and sexes. Gilts (n = 21) and barrows (n = 9) of the Landrace × Yorkshire (LY; n = 15) and Landrace/Yorkshire × Landrace/Duroc (LYLD; n = 15) breeds were subjected to a novel object test (NOT) and a novel arena test (NAT). Basal ANS state differed in pigs across breeds but not sexes. Landrace × Yorkshire pigs had a significantly lower basal heart rate (HR) and low-frequency band (LF) with a higher root mean square of successive interbeat intervals (RMSSD) and high-frequency band (HF) than LYLD pigs. In the NOT, despite having similar cardiac responses, gilts had a longer duration of contact with a novel object, higher lying and standing duration, and a lower duration of walking compared with barrows. In the NAT, we found similar behaviour across sexes but a different degree of ANS state, with barrows having a significantly higher increase in LF/HF (power of the low frequency component divided by the power of the high-frequency band) compared with gilts. Landrace/Yorkshire × Landrace/Duroc pigs showed longer duration of contact with a novel object in the NOT accompanied by less lying and standing than LY pigs in both tests. No difference in ANS activation between breeds was found in the NOT. In the NAT, HR increased more from baseline to testing in LY pigs than in LYLD pigs. There is a complex and often contradictory nature of relationships between behaviour and cardiac responses to novelty in pigs of different breeds and sexes.

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

“…In that study, pigs were selected from a single farm and control pigs were selected from the pens with no tail-biting outbreaks, which could explain the inconsistency between the studies. When assessing at the novel-object and the novel-arena test situations, it was interesting to see that, although the behaviour responses were indicative of emotional experiences and the cardiovascular responses were induced (Zupan et al, 2012(Zupan et al, , 2016, no difference in the activation of HPA-axis was found. We found similar results in pigs of different breeds and sexes.…”

“…We documented that the activity of the autonomic nervous system, especially the suppression of parasympathetic tone, indicates that some pigs may have a dysfunctional autonomic regulation (Zupan et al, 2012). Additionally, the results indicated that in tail-biting pens, pigs of different sexes and breeds possess different autonomic flexibility (Zupan et al, 2016). In this paper, we tested pigs in a human-response test, a novel object test, a novel arena test, and during transportation and assessed the activation of stress-axis, using a non-invasive method to measure salivary cortisol concentrations.…”

“…We studied the same pigs and commercial farms as described previously (Zupan et al, 2012(Zupan et al, , 2016. Farm visits followed a report of tail-biting outbreaks on three commercial Norwegian farms.…”

“…Pigs involved in tail biting suffer from inflammatory responses (Heinonen et al, 2010) and fearfulness (Zupan et al, 2012(Zupan et al, , 2016, thus having impaired physical and psychological health.…”

“…In this paper, we tested pigs in a human-response test, a novel object test, a novel arena test, and during transportation and assessed the activation of stress-axis, using a non-invasive method to measure salivary cortisol concentrations. By performing different behaviour responses to environmental situations (Zupan et al, 2012(Zupan et al, , 2016, we expected animals to express different stress susceptibility, with tail biters and victims to have higher cortisol levels than control pigs. Equally, by investigating diurnal rhythm in cortisol release, we expected the genotypic characteristics of the pigs to affect their circadian rhythm.…”