Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: June 28, 2011
Publication Date: July 11, 2011
Citation: Lay Jr, D.C., Marchant Forde, R.M., Marchant Forde, J.N., Hogan, D.F. 2011. Use of heart rate variability differentiates between physical and psychological states. Journal of Animal Science. Proceedings ASAS 2011. Technical Abstract: The major goal of animal welfare scientists is to determine when animals are experiencing a state of good welfare or poor welfare. The goal of this research was to determine if measures of heart rate variability can be used to differentiate whether animals are experiencing differing states of physical stress. Fifteen, 4-month-old pigs were implanted with telemetric devices to collect electrocardiogram data. Nine of these pigs served as ‘non-challenged’ control pigs; while the remaining 6 were trained to exercise on a treadmill and challenged with each of the 4 treadmill ‘speeds’ in a randomized design. Data were collected while pigs were: 1) resting in their home pen (Home); 2) standing on the treadmill but not exercising (Stand); 3) exercise at low speed (Low, 1 km/h); 4) exercise at medium speed (Medium, 3 km/h); or 5) exercise at high speed (High, 5 km/h). Series of 512 successive inter-beat intervals (IBI) were subject to time and frequency domain analyses followed by a factorial analysis of test × sex with mixed models and Tukey’s post-hoc test. Mean heart rate (HR) was higher as exercise increased ( P < 0.001; Stand, 115 ± 6; Low, 171 ± 9; Medium, 201 ± 10; High, 222 ± 9 bpm); but was intermediate for pigs in the home pen (142 ± 4 bpm). Mean IBI was lower as exercise increased (P < 0.001; Stand, 529 ± 25 ; Low, 356 ± 19; Medium, 301 ± 14; High, 272 ± 11 ms); with pigs in the home pen being intermediate (424 ± 12 ms). The root mean square of successive differences (RMSSD, index of vagal cardiac control) showed a similar response (P < 0.001; Stand, 12.0 ± 1.0; Low, 8.0 ± 1.0; Medium, 4.8 ± 0.7; High, 5.0 ± 0.5 ms), with pigs in the home pen again being intermediate (8.7 ± 0.9 ms). In contrast, sympathovagal balance (ratio of low frequency/high frequency power) was not different in exercised pigs (P > 0.10; Stand, 3.1 ± 0.4; Low, 3.7 ± 1.2; Medium, 4.1 ± 1.3; High, 3.2 ± 0.6); while pigs in their home pen had a LF/HF ratio of 5.5 ± 0.9. These data indicate that measures of heart rate variability are a sensitive measure in pigs to differentiate between differing physiologic states and may prove useful to differentiate between affective states.