About the project

This project explores the hypothesis that daily physical activity and free access to hay—both separately and in combination, promote gut health (by preventing gastric ulcers and gut inflammation), affective state, neural plasticity in the hippocampus and frontal cortex, cognitive competence and overall pig welfare. By identifying key behavioral and physiological measures, we aim to examine their relationship with gut health and welfare indicators in finishing pigs.

Our primary prediction is that both physical activity and hay enrichment will increase behaviors associated with positive affective states while reducing those linked to negative affective states. Consequently, we expect welfare protocol data of finishing pigs to reflect higher welfare in experimental treatment groups compared to control groups (e.g. Andersen et al., 2023).

Additionally, we predict that pigs receiving these enrichments will perform better in a learning task, displaying more proactive and synchronous problem solving. Furthermore, we anticipate that both interventions will enhance markers of gut health and neural plasticity relative to control groups.

Our final prediction is that combining daily activity and hay yields greater benefits than either intervention alone, as both are expected to positively influence digestion, gut health, and brain function. If confirmed, these findings could have broad implications for improving pig welfare in commercial farming by promoting enrichment strategies that support both physical and mental well-being. The research will also contribute to a growing body of research on the gut-brain connection and its relevance across species, including humans.

• Objectives

  The project will be organized into the following four work packages:

  WP 1. Behaviour and welfare (WP leader Inger Lise Andersen): Effects of physical activity and ad libitum access to hay, separately and in combination, on behavioural indicators of affective states, social dynamics, behavioural responses in a task measuring cognitive abilities, and welfare protocol indicators (data collected for PhD 1, Biovit faculty, NMBU). Individual variation in physical activity and distance moved will be an essential measure. We predict that both interventions will increase behaviors associated with positive affective states, such as play, exploration, friendly social contact, rest, and confidence around (i.e. low fear of) humans, while reducing behaviors linked to negative affective states, including tail- and ear-biting, aggressive conflicts, and fear responses. As a result, we expect pigs in the experimental treatment groups to exhibit higher welfare scores than those in the control groups. Additionally, we anticipate greater success, increased social tolerance and more goal-directed behaviour in a learning task among pigs receiving enrichment compared to control groups. Overall, we predict that the positive effects on behavior and welfare parameters will be most pronounced when both enrichment strategies are combined.

  WP2. Cortisol and gut health (WP leader Nicol F. Nyquist): Effects of physical activity and ad libitum access to hay, separately and in combination, on salivary cortisol, gut inflammation, and the incidence of stomach ulcers (data collected for PhD 2, Veterinary faculty, NMBU). We investigate whether and in what way cortisol levels will be affected by the treatments throughout the finishing period as cortisol may also increase due to increased activity. We predict higher stress resilience, as indicated by a more rapid return of cortisol to baseline levels after a stress challenge, and a lower prevalence and severity of stomach ulcers identified after slaughter compared to those in the control groups. Likewise, we expect a reduced incidence of inflammation in the stomach and intestines in pigs receiving enrichment. We also anticipate that a combination of physical activity and free access to hay will have the strongest impact in reducing cortisol levels and enhancing gut health. Data on individual variation in hay consumption, physical activity and distance moved will be important for interpreting these findings.

  WP3. Neural plasticity (WP leader Janicke Nordgreen): Effects of physical activity and ad libitum access to hay on neural plasticity in hippocampus and prefrontal cortex (Data analysed by Prof. Alistair Lawrence`s group in collaboration with the project team). We predict that both hay and physical activity enrichment treatments will lead to an upregulation of genes associated with neuronal plasticity in the frontal cortex and hippocampus compared to control groups and that combining both sources of enrichment will give the most pronounced effect. In addition, in line with previous work on environmental enrichment, we predict to see a reduction in markers of neuroinflammation; the combination of which ultimately supports cognitive functioning, stress resilience and emotional regulation.

  WP4 (WP leader Ruth Newberry): Relationships between variables measured in WP1, 2 and 3 (PhD 1 + PhD 2). In this WP, we explore relationships between behavioural responses, welfare protocol variables, cognitive test variables, cortisol, and gut and brain health measures from individual pigs using path, network and generalized linear mixed model analyses. For instance, we consider which behavioral indicators (e.g. play, distance moved, hay consumption, social status, learning ability) can serve as reliable non-invasive indicators of gut and/or brain health. We also examine how patterns of salivary cortisol secretion, indicating stress resilience, are related to the other measures. We predict a strong correlation between gut health parameters and neural plasticity, reinforcing the gut-brain axis. We also predict that pigs experiencing greater neural plasticity will perform better in cognitive tasks, showing improved learning, memory, and adaptability. In general, we aim to identify non-invasive indicators of good health and welfare that can be used in a systematic way to predict future health and welfare outcomes.

• Participants

  NMBU participants

  External participants

  Animalia
  Rasmus B. Jensen, Aarhus university
  Alistair Lawrence, University of Edinburgh