Individual behavioral and physiological strategies in pigs

Physiol Behav. 1994 Jan;55(1):39-46. doi: 10.1016/0031-9384(94)90007-8.

Abstract

Previous experiments demonstrated consistent individual behavioral differences in pigs. Some showed a more active behavioral response (so-called A/R pigs), others a more passive behavioral response (so-called NA/NR pigs). In the present study we selected 32 A/R and 32 NA/NR individuals and tested them individually in an open field at 3 (OF1) and 8 weeks of age (OF2). Individual response patterns were remarkably consistent between OF1 and OF2. While more A/R than NA/NR pigs made escape attempts, the A/R ones vocalized less, and were less inhibited to approach novel objects in OF1 and OF2, although they spent less time in exploring these objects than NA/NR pigs. Cortisol (CS) level after OF1 increased in A/R pigs but did not change in NA/NR ones, while CS level in OF2 remained constant in A/R pigs but decreased in NA/NR pigs. CS response to ACTH1-39 was measured at 3 and 8 weeks of age but did not differ between types. Basal CS level was higher in NA/NR than in A/R pigs and accompanied by adrenal hypertrophy. Mean heart rate (HR) was higher of A/R pigs compared to NA/NR ones in two backtests. HR of A/R pigs substantially increased (23.9 bpm = 15.5%) in reaction to the novel object in OF2, while HR of NA/NR ones only slightly increased (4.5 bpm = 2.9%), or even decreased (bradycardia). A/R pigs had more often heart deviations than NA/NR ones. The present study demonstrates that the two behavioral strategies of pigs are characterized by consistent differences in behavioral, physiological, and endocrine responses to conflict situations.

MeSH terms

  • Adaptation, Psychological / physiology*
  • Adrenal Glands / pathology
  • Adrenocorticotropic Hormone / physiology
  • Aggression / physiology
  • Animals
  • Arousal / physiology*
  • Behavior, Animal / physiology*
  • Exploratory Behavior / physiology
  • Heart Rate / physiology
  • Hydrocortisone / blood
  • Individuality*
  • Male
  • Motor Activity / physiology*
  • Myocardium / pathology
  • Organ Size / physiology
  • Parasympathetic Nervous System / physiology
  • Social Environment
  • Stress, Psychological / complications
  • Swine
  • Sympathetic Nervous System / physiology

Substances

  • Adrenocorticotropic Hormone
  • Hydrocortisone