SAFEGUARDING WELL-BEING OF FOOD PRODUCING ANIMALS
Location: Livestock Behavior Research
Title: Heart Rate Variability – a Tool to Differentiate Positive and Negative Affective States in Pigs?
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 25, 2010
Publication Date: July 11, 2010
Citation: Poletto, R., Marchant-Ford, R.M., Marchant Forde, J.N., Rault, J., Hogan, D.F., Lay Jr, D.C. 2010. Heart Rate Variability – a Tool to Differentiate Positive and Negative Affective States in Pigs? [abstract]. Journal of Animal Science. 88:415(Suppl. 2).
The causal neurophysiological processes, such as autonomic nervous system activity, that mediate behavioral and physiological reactivity to an environment have largely been ignored. Heart rate variability (HRV) analysis is a clinical diagnostic tool used to assess affective states (stressful and pleasant) in humans, but its application is very limited in farm animals. The aim of this experiment was to determine if HRV could be used to differentiate affective states in swine. Ten, 4-month old male and female pigs underwent surgery to place an intracardiac ECG lead via the jugular vein, attached to a biotelemetry device implanted subcutaneously. Pigs had a 3-wk recovery period prior to data collection. Negative state was induced by restraining pigs for 1h in metabolism crates in the same room. Positive state was induced by allowing pigs’ access to the room’s hallway for 10 min. Behavior and ECG data were recorded; restraint test: a 512-beat section of interbeat intervals (IBI) was extracted for HRV analysis while pigs were inactive; hallway test: IBI sections were extracted during a combination of active play, exploratory, and lying behaviors. Data were analyzed using time and frequency domain analysis, followed by a factorial analysis of test × sex with mixed models and tukey’s post-hoc test. Average HR was lower for restraint than the hallway test (121.7±4.4 vs. 162.4±4.3 bpm; P < 0.01), while RMSSD, index of vagal cardiac control, was higher for restraint than for hallway test (11.0±1.0 vs. 7.0±0.9 ms; P < 0.05). Female pigs had higher normalized low frequency (LF) power than males (65.1±3.9 vs. 43.9±4.2 msec2/Hz; P < 0.01). Normalized high frequency (HF) power was lower in hallway play than in restraint (4.2±1.8 vs. 14.1±1.9 msec2/Hz; P < 0.01). Sympathovagal balance (LF/HF) was higher during hallway play compared to restraint (P < 0.01). Female pigs showed primarily sympathetic modulation of HR, while restraint resulted in greater parasympathetic control of cardiac function. Results indicate that HRV can be used to distinguish different degrees of activity/states in pigs. Further research will assist to identify distinct autonomic response patterns to different well-being states in pigs and other farm animals.