Individual behavioral and physiological strategies in pigs

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 th...

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Bibliographic Details
Published in:	Physiology & behavior Vol. 55; no. 1; p. 39
Main Authors:	Hessing, M J, Hagelsø, A M, Schouten, W G, Wiepkema, P R, van Beek, J A
Format:	Journal Article
Language:	English
Published:	United States 01-01-1994
Subjects:	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
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Summary:	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.
ISSN:	0031-9384
DOI:	10.1016/0031-9384(94)90007-8