Validation of a cardiac monitor for measuring heart rate variability in adult female pigs: accuracy, artefacts and editing

Evaluating the Net Energy Requirements for Maintenance Based on Indirect Calorimetry and Heart Rate Monitoring in Gestating Sows

The objectives of this study were (1) to determine the net energy requirements for the maintenance of gestating sows based on indirect calorimetry, and (2) to explore the feasibility of predicting the net energy requirements for the maintenance of gestating sows based on daily heart rate monitoring. In Exp. 1, six Landrace × Yorkshire crossbred reproductive sows with an initial body weight of 229.5 ± 14.9 kg at d 56 of gestation were randomly assigned to six diverse energy feeding levels using a 6 × 6 Latin square design. The experimental diet was formulated using corn, soybean meal, and wheat bran as major ingredients, and the six feeding levels were set as 1.2, 1.4, 1.6, 1.8, 2.0, and 2.2 times metabolizable energy for maintenance (100 kcal ME/kg BW0.75·d-1), respectively. The animal trial lasted for six periods with 9 days per period, encompassing 5 days of adaptation, 3 days of calorimetry in fed state, and 1 day of calorimetry in fasting state. In Exp. 2, six Landrace × Yorkshire crossbred pregnant sows with an initial body weight of 232.5 ± 12.5 kg at d 64 were fed a corn-soybean meal diet. All sows were tested in a respiratory calorimetry chamber for a 4 day calorimetry test. The heat production of the gestation sows was measured every 5 min using indirect calorimetry, and the heart rate of the gestating sows was recorded every minute using a belt-shape monitor. The results showed that the net energy requirements for the maintenance of gestating sows significant increased as the gestational stage progressed (p < 0.05), and a linear regression model revealed the average net energy requirement for the maintenance of gestating sows was 410 kJ/BW0.75 d-1 during late gestation (days 70-110). Moreover, the average heart rate of the gestating sows was 84 bpm, and the mathematical model developed to predict the net energy requirements for the maintenance of gestating sows was NEm(kcal/h)=19901+exp⁡[136-HR(bpm)43]. In conclusion, the average net energy requirement for the maintenance of sows during late gestation was 410 kJ/BW0.75 d-1, and the utilization of the heart rate monitoring method was found to provide a relevant, accurate prediction for the net energy requirements of sows.

Cortisol levels, heart rate, and autonomic responses in horses during repeated road transport with differently conditioned trucks in a tropical environment

Horse's stress responses have been reported during road transport in temperate but not tropical environments. Therefore, this study measured cortisol levels, heart rate (HR), and heart rate variability (HRV) in horses during medium-distance road transport with different truck conditions in a tropical environment. Six horses were repeatedly transported in either air-conditioned trucks with full (ATF) or space (ATS) loads or non-air-conditioned trucks with full (N-ATF) and space (N-ATS) loads. Blood cortisol was determined beforehand and 5, 30, and 90 minutes post-transport. HR and HRV were assessed pre-transport and at 15-minute intervals until 90 minutes post-transport. Cortisol levels increased significantly in N-ATS horses (but non-significantly in ATF, ATS, and N-ATF horses) at 5 minutes post-transport and returned to baseline by 30 minutes post-transport. Predominant parasympathetic nervous system (PNS) activity was observed during the first few hours and returned to baseline until the destination was reached. A recurrent, increased PNS activity was detected post-transport. Interaction effects of air condition-by-loading condition-by-time, air condition-by-time, and separate effects of air condition and time were observed on HR and various HRV variables during transport. A transient increase in beat-to-beat intervals, coinciding with decreased HR, was observed in ATF horses. The PNS index increased, corresponding to a decreased sympathetic nervous system index, in ATS horses during transport. We suggest that medium-distance road transport causes no stress for transport-experienced horses in a tropical environment. Air and loading conditions impacted hormonal and autonomic modulation, causing different responses in horses transported in differently conditioned trucks.

Are infrared thermography, feeding behavior, and heart rate variability measures capable of characterizing group-housed sow social hierarchies?

Group gestation housing is quickly becoming standard practice in commercial swine production. However, poor performance and welfare in group housed sows may result from the formation and maintenance of the social hierarchy within the pen. In the future, the ability to quickly characterize the social hierarchy via precision technologies could be beneficial to producers for identifying animals at risk of poor welfare outcomes. Therefore, the objective of this study was to investigate the use of infrared thermography (IRT), automated electronic sow feeding systems, and heart rate monitors as potential technologies for detecting the social hierarchy within five groups of sows. Behavioral data collection occurred for 12 h after introducing five sow groups (1-5; n = 14, 12, 15, 15, and 17, respectively) to group gestation housing to determine the social hierarchy and allocate individual sows to 1 of 4 rank quartiles (RQ 1-4). Sows within RQ1 were ranked highest while RQ4 sows were ranked lowest within the hierarchy. Infrared thermal images were taken behind the neck at the base of the ear of each sow on days 3, 15, 30, 45, 60, 75, 90, and 105 of the experiment. Two electronic sow feeders tracked feeding behavior throughout the gestation period. Heart rate monitors were worn by 10 randomly selected sows per repetition for 1 h prior to and 4 h after reintroduction to group gestation housing to collect heart rate variability (HRV). No differences were found between RQ for any IRT characteristic. Sows within RQ3 and RQ4 had the greatest number of visits to the electronic sow feeders overall (P < 0.04) but spent shorter time per visit in feeders (P < 0.05) than RQ1 and RQ2 sows. There was an interaction of RQ with hour for feed offered (P = 0.0003), with differences between RQ occurring in hour 0, 1, 2, and 8. Higher-ranked sows (RQ1 and RQ2) occupied the feeder for longer during the first hour than lower ranking sows (RQ3 and RQ4; P < 0.04), while RQ3 sows occupied the feeder longer than RQ1 sows during hour 6, 7, and 8 (P < 0.02). Heart beat interval (RR) collected prior to group housing introduction differed between RQ (P < 0.02 for all), with RQ3 sows exhibiting the lowest RR, followed by RQ4, RQ1, and RQ2. Rank quartile also affected standard deviation of RR (P = 0.0043), with RQ4 sows having the lowest, followed by RQ1, RQ3, and RQ2 sows. Overall, these results indicate that feeding behavior and HRV measures may be capable of characterizing social hierarchy in a group housing system.

Validation of a new smart textiles biotechnology for heart rate variability monitoring in sheep

Robust Animal-Based Measures (ABMs) are fundamental in order to assess animal welfare, however in semi-extensive sheep farming systems is not easy to collect ABMs without inducing additional stress in the animals. Heart rate variability (HRV) is a non-invasive technique of assessing stress levels related to animal welfare. It is considered a sensitive indicator of the functional regulatory characteristics of the autonomic nervous system. Several studies investigated the use of HRV for welfare assessment in dairy cows while research on sheep is scarce. Moreover, assessing HRV in small ruminants at pasture is critical because of the lack of a solution adoptable for field conditions. This study aimed to evaluate if a smart textiles technology is comparable to a Standard base-apex electrocardiogram (ECG) for measuring HRV in small ruminants. Eight healthy Massese dairy sheep were recruited. Standard base-apex ECG and smart textiles technology (Smartex ECG) were simultaneously acquired for 5 min in the standing, unsedated, unclipped sheep. The ECG tracings were recorded when animals were standing quietly. The Bland-Altman test and the linear regression analysis were applied after parameter extraction in time, frequency, and non-linear methods to compare Smartex against standard base-apex ECG systems. The Bland-Altman test was applied to all HRV extracted parameters (Mean RR, pNN50, RMSSD, LF/HF, SampEn, SD1, SD2, stdRR) to evaluate the agreement between the two different instruments, and a linear regression analysis was performed to evaluate the relationship between the two methods. The smart textiles biotechnology was simple to wear and clean. It can be worn without using glue and without shaving the sheep's wool, limiting animal handling and stress. Bland Altman test reported a robust agreement between the two systems. In fact, the regression analysis of HRV parameters showed that half of the parameters recorded had an R2 coefficient &gt;0.75. Results also showed a very small reproducibility coefficient that indicated that the two methods were really close to each other. Smartex textiles technology can be used for HRV evaluation in sheep species as a potential ABM for animal welfare assessment.

Agreement between two photoplethysmography-based wearable devices for monitoring heart rate during different physical activity situations: a new analysis methodology

Wearables are being increasingly used to monitor heart rate (HR). However, their usefulness for analyzing continuous HR in research or at clinical level is questionable. The aim of this study is to analyze the level of agreement between different wearables in the measurement of HR based on photoplethysmography, according to different body positions and physical activity levels, and compared to a gold-standard ECG. The proposed method measures agreement among several time scales since different wearables obtain HR at different sampling rates. Eighteen university students (10 men, 8 women; 22 ± 2.45 years old) participated in a laboratory study. Participants simultaneously wore an Apple Watch and a Polar Vantage watch. ECG was measured using a BIOPAC system. HR was recorded continuously and simultaneously by the three devices, for consecutive 5-min periods in 4 different situations: lying supine, sitting, standing and walking at 4 km/h on a treadmill. HR estimations were obtained with the maximum precision offered by the software of each device and compared by averaging in several time scales, since the wearables obtained HR at different sampling rates, although results are more detailed for 5 s and 30 s epochs. Bland–Altman (B-A) plots show that there is no noticeable difference between data from the ECG and any of the smartwatches while participants were lying down. In this position, the bias is low when averaging in both 5 s and 30 s. Differently, B-A plots show that there are differences when the situation involves some level of physical activity, especially for shorter epochs. That is, the discrepancy between devices and the ECG was greater when walking on the treadmill and during short time scales. The device showing the biggest discrepancy was the Polar Watch, and the one with the best results was the Apple Watch. We conclude that photoplethysmography-based wearable devices are suitable for monitoring HR averages at regular intervals, especially at rest, but their feasibility is debatable for a continuous analysis of HR for research or clinical purposes, especially when involving some level of physical activity. An important contribution of this work is a new methodology to synchronize and measure the agreement against a gold standard of two or more devices measuring HR at different and not necessarily even paces.

Assessing the Relationship Between Emotional States of Dogs and Their Human Handlers, Using Simultaneous Behavioral and Cardiac Measures

Negative stress due to human handling has been reported for a number of domestic animals, including dogs. Many companion dogs display significant stress during routine care in the veterinary clinic, risking injury to staff and potentially compromising the quality of care that these dogs receive. On the other hand, positive interactions with humans can have a beneficial effect on dogs, particularly in stressful situations such as animal shelters. Research has shown that dogs can detect human emotions through visual, auditory, and chemical channels, and that dogs will exhibit emotional contagion, particularly with familiar humans. This study investigated relationships between emotional states of dogs and unfamiliar human handlers, using simultaneous measures of cardiac activity and behavior, during two sessions of three consecutive routine handling sets. Measures of cardiac activity included mean heart rate (HR_mean), and two measures of heart rate variability (HRV): the root mean square of successive differences between normal heartbeats (RMSSD); and the high frequency absolute power component of HRV, log transformed (HF_log). We also assessed human handlers' emotional state during handling sessions following an intervention designed to reduce stress, compared with sessions conducted on a different day and following a control activity. Polar H10 cardiac sensors were used to simultaneously record cardiac activity for both canine and human participants, and behavioral data were collected via digital video. The strongest influence on the dogs' stress levels in our study was found to be increasing familiarity with the setting and the handler; HR_mean and SI decreased, and HRV (as RMSSD) increased, significantly from the first to the third handling set. Canine HRV (as HF_log) was also highest in set 3, although the difference was not statistically significant. There were no strong patterns found in the human cardiac data across handling set, session, or by pre-handling activity. We did not find consistent support for emotional contagion between the dogs and their handlers in this study, perhaps due to the brief time that the dogs spent with the handlers. Recommendations for application to dog handling, and limitations of our methods, are described.

Dog-Owner Relationship, Owner Interpretations and Dog Personality Are Connected with the Emotional Reactivity of Dogs

We evaluated the effect of the dog-owner relationship on dogs' emotional reactivity, quantified with heart rate variability (HRV), behavioral changes, physical activity and dog owner interpretations. Twenty nine adult dogs encountered five different emotional situations (i.e., stroking, a feeding toy, separation from the owner, reunion with the owner, a sudden appearance of a novel object). The results showed that both negative and positive situations provoked signs of heightened arousal in dogs. During negative situations, owners' ratings about the heightened emotional arousal correlated with lower HRV, higher physical activity and more behaviors that typically index arousal and fear. The three factors of The Monash Dog-Owner Relationship Scale (MDORS) were reflected in the dogs' heart rate variability and behaviors: the Emotional Closeness factor was related to increased HRV (p = 0.009), suggesting this aspect is associated with the secure base effect, and the Shared Activities factor showed a trend toward lower HRV (p = 0.067) along with more owner-directed behaviors reflecting attachment related arousal. In contrast, the Perceived Costs factor was related to higher HRV (p = 0.009) along with less fear and less owner-directed behaviors, which may reflect the dog's more independent personality. In conclusion, dogs' emotional reactivity and the dog-owner relationship modulate each other, depending on the aspect of the relationship and dogs' individual responsivity.

[Validation of the telemetric BioHarnessTM 3 chest strap for measurement of Heart Rate Variability (HRV) in pigs]

OBJECTIVE

The aim of this clinical study was to determine whether the telemetric BioHarness 3.0^TMchest strap (Zephyr Technology, Medtronic, Annapolis, USA), designed for use in humans and specialized for heart rate variability (HRV) analysis, could be used to accurately measure Heart Rate Variability (HRV) in pigs.

METHODS

The R-wave intervals (RR-intervals) of the BioHarness 3.0^TM electrocardiogram (ECG) were compared with those of the widely used telemetric ECG Televet^®100 device (Engel Engineering GmbH, Heusenstamm, Germany). Measurements were performed under general anesthesia, to ensure continuous data collection due to the risk of detachment in adhesive electrodes of the Televet^®100. The 2 devices were started simultaneously and measurements were taken 6 times in a row for 5 minutes, respectively. The data were collected from 5 male growing pigs. Following artifact correction resp. deletion 5321 RR paired data within a 3 digit range (ms) were analyzed statistically.

RESULTS

The Lin Concordance-Correlation-Analysis after Lin (correlation coefficient 0.95), and the Bland-Altman-Analysis (RR distance differences + 0.3 ms) demonstrated a very good measurement compliance.

CONCLUSION

This data suggests the BioHarness chest strap may be used for wireless HRV analysis in pigs as was shown in a follow up study in non-anesthetized pigs.

Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in nonpregnant, mid-gestation, and late-gestation sows

Characterizing the sow physiological response to an increased heat load is essential for effective heat stress mitigation. The study objective was to characterize the effects of a 400-min heating episode on sow heart rate variability (HRV) at different reproductive stages. HRV is a commonly used noninvasive proxy measure of autonomic function. Twenty-seven sows were enrolled in the study according to their gestation stage at time of selection: 1) nonpregnant (NP; n = 7), 2) mid-gestation (MID; 57.3 ± 11.8 d gestation; n = 11), and 3) late-gestation (LATE; 98.8 ± 4.9 d gestation; n = 8). The HRV data utilized in the study were collected from each pig as the dry bulb temperature in the room increased incrementally from 19.84 ± 2.15 °C to 35.54 ± 0.43 °C (range: 17.1-37.5 °C) over a 400-min period. After data collection, one 5-min set of continuous heart rate data were identified per pig for each of nine temperature intervals (19-20.99, 21-22.99, 23-24.99, 25-26.99, 27-28.99, 29-30.99, 31-32.99, 33-34.99, and 35-36.99 °C). Mean inter-beat interval length (RR), standard deviation of r-r intervals (SDNN), root mean square of successive differences (RMSSD), high frequency spectral power (HF), sample entropy (SampEn), short-term detrended fluctuation analysis (DFAα1), and three measures (%REC, DET, LMEAN) derived from recurrence quantification analysis were calculated for each data set. All data were analyzed using the PROC GLIMMIX procedure in SAS 9.4. Overall, LATE sows exhibited lower RR than NP sows (P < 0.01). The standard deviation of r-r intervals and RMSSD differed between each group (P < 0.01), with LATE sows exhibiting the lowest SDNN and RMSSD and NP sows exhibiting the greatest SDNN and RMSSD. Late-gestation sows exhibited lower HF than both MID and NP sows (P < 0.0001), greater DFA values than NP sows (P = 0.05), and greater DET compared to MID sows (P = 0.001). Late-gestation also sows exhibited greater %REC and LMEAN compared to MID (P < 0.01) and NP sows (all P < 0.01). In conclusion, LATE sows exhibited indicators of greater autonomic stress throughout the heating period compared to MID and NP sows. However, temperature by treatment interactions were not detected as dry bulb increased. Future studies are needed to fully elucidate the effect of gestational stage and increasing dry bulb temperature on sow HRV.

Effects of small milking stalls on stress responses in dairy cows during milking in group milking parlors

Milking stall dimensions have not been adapted to the increase in cow body size caused by selection for better milking performance over the past decades. Improper milking stall dimensions might limit cow comfort, could lead to stress responses during milking and thus could negatively affect cow welfare. A crossover study was conducted in an experimental milking parlor that was converted from a herringbone (HB) to a side-by-side (SBS) parlor. The milking stall dimensions were modified in length and width and for HB also in depth (perpendicular distance between rump rail and breast rail). The stall dimensions applied during the experiments ranged from much smaller than common in European dairy farming to much larger. Treatments were applied for 2 wk per milking parlor type. In each milking parlor type, a total of 30 cows, kept in 2 groups were observed during milking for behavioral and physiological stress responses and for milking performance. In addition, milk cortisol levels and somatic cell counts were measured at the end of the 2-wk period. Outcome variables were selected based on a principal component analysis and analyzed using mixed effects models reflecting the experimental design. The results showed that the first cow per milking batch required more time (on average >40 s) to enter very small HB stalls than to enter small, large and very large stalls (<30 s). Also, cows yielded more milk per milking in very small and very large HB stalls than in the small and large milking stall dimensions [very small: 15.8 kg; 95% confidence interval (CI), 14.2-17.4 kg); small: 14.3 kg (95% CI, 12.8-15.9 kg); large: 14.6 kg (95% CI, 13.1-16.1 kg); very large: 16.1 kg (95% CI, 14.6-17.6 kg)]. The other behavioral, physiological and milk flow parameters as well as udder health were not affected by stall dimensions. For the SBS parlor, effects of milking stall dimensions were not detectable in any of the parameters. Despite the strong avoidance behavior to enter the milking parlor (measured as latency), no acute stress responses were found during milking. However, the study cannot exclude long-term effects of narrow stall dimensions on stress levels and possibly udder health, which should be investigated in future studies.

Heart rate as a measure of emotional arousal in evolutionary biology

How individuals interact with their environment and respond to changes is a key area of research in evolutionary biology. A physiological parameter that provides an instant proxy for the activation of the automatic nervous system, and can be measured relatively easily, is modulation of heart rate. Over the past four decades, heart rate has been used to assess emotional arousal in non-human animals in a variety of contexts, including social behaviour, animal cognition, animal welfare and animal personality. In this review, I summarize how measuring heart rate has provided new insights into how social animals cope with challenges in their environment. I assess the advantages and limitations of different technologies used to measure heart rate in this context, including wearable heart rate belts and implantable transmitters, and provide an overview of prospective research avenues using established and new technologies, with a special focus on implications for applied research on animal welfare. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Thermoregulatory and physiological responses of nonpregnant, mid-gestation, and late-gestation sows exposed to incrementally increasing dry bulb temperature

Gestating sows may be more susceptible to increasing dry bulb temperatures (TDB) due to greater metabolic heat production and increased body mass, especially as gestation advances. However, there are few studies on the thermoregulatory and physiological responses of sows at differing gestation stages exposed to gradually increasing temperatures. The study objective was to determine the thermoregulatory and physiological responses of nonpregnant (n = 12; parity 3.27 ± 0.86), mid-gestation (59.7 ± 9.6 d pregnant, n = 12; parity 3.25 ± 0.83), and late-gestation (99.0 ± 4.8 d pregnant, n = 12; parity 3.33 ± 0.75) sows exposed to increasing TDB. Prior to the experiment (5.0 ± 0.7 d), jugular catheters were placed in all sows. During the experiment, the TDB was increased incrementally by 2.45 ± 0.43 °C every 60 min from 19.84 ± 2.15 to 35.54 ± 0.43 °C over 400 min, and relative humidity was recorded at 40.49 ± 18.57%. Respiration rate (RR), heart rate (HR), skin temperature, and vaginal temperature were measured, and blood samples were obtained via the jugular catheter every 20 min. Data were analyzed using PROC MIXED in SAS 9.4. RR increased at a lower TDB (P < 0.01) in late-gestation sows compared with mid-gestation and nonpregnant sows, but no differences were detected between mid-gestation and nonpregnant sows. Overall, late-gestation sows had greater RR (P < 0.01; 23 ± 2 breaths per min [brpm]) compared with mid-gestation (16 ± 2 brpm) and nonpregnant (15 ± 2 brpm) sows. Late-gestation sows had an overall greater HR (P < 0.01; 84 ± 5 beats per min [bpm]) than mid-gestation (76 ± 5 bpm) and nonpregnant (69 ± 5 bpm) sows. Late-gestation sows had overall reduced bicarbonate and total carbon dioxide levels (P = 0.02; 23.89 ± 1.97 and 25.41 ± 2.07 mmol/L, respectively) compared with mid-gestation (27.03 ± 1.97 and 28.58 ± 2.07 mmol/L, respectively) and nonpregnant (26.08 ± 1.97 and 27.58 ± 2.07 mmol/L, respectively) sows. Moreover, late-gestation sows had overall greater nitric oxide levels (P < 0.01; 248.82 ± 34.54 µM) compared with mid-gestation (110.47 ± 34.54 µM) and nonpregnant (41.55 ± 34.54 µM) sows. In summary, late-gestation sows appear to be more sensitive to increasing TDB as indicated by thermoregulatory and physiological responses when compared with mid-gestation or nonpregnant sows. The results from this study provide valuable information regarding thermoregulatory thresholds of sows at differing gestation stages.

An external telemetry system for recording resting heart rate variability and heart rate in free-ranging large wild mammals

Measures of heart rate variability (and heart rate more generally) are providing powerful insights into the physiological drivers of behaviour. Resting heart rate variability (HRV) can be used as an indicator of individual differences in temperament and reactivity to physical and psychological stress. There is increasing interest in deriving such measures from free ranging wild animals, where individuals are exposed to the natural and anthropogenic stressors of life. We describe a robust, externally mounted heart rate monitor for use in wild mammals, deployed here on wild breeding adult female grey seals (Halichoerus grypus), that delivers millisecond precise measures of inter beat intervals (IBIs), allowing computation of resting HRV parameters. Based on Firstbeat™ heart rate belts, our system allows for remote, continuous recording of IBI data from over 30 individuals simultaneously at ranges of up to 200m. We assessed the accuracy of the IBI data provided by the Firstbeat™ system using concurrent IBI data derived from in-field electrocardiogram (ECG) recordings. Bland-Altmann analyses demonstrated high correspondence between the two sets of IBI data, with a mean difference of 0.87±0.16ms. We used generalized additive mixed-effects models to examine the impact of the default Firstbeat™ software artefact correction procedure upon the generation of anomalous data (flats and stairs). Artefact correction and individual activity were major causes of flats and stairs. We used simulations and models to assess the impact of these errors on estimates of resting HRV and to inform criteria for subsampling relatively error free IBI traces. These analyses allowed us to establish stringent filtering procedures to remove traces with excessive numbers of artefacts, including flats and stairs. Even with strict criteria for removing potentially erroneous data, the abundance of data yielded by the Firstbeat™ system provides the potential to extract robust estimates of resting HRV. We discuss the advantages and limitations of our system for applications beyond the study system described here.

Contact-Free Pulse Signal Extraction from Human Face Videos: A Review and New Optimized Filtering Approach

In this chapter, we review methods for video-based heart monitoring, from classical signal processing approaches to modern deep learning methods. In addition, we propose a new method for learning an optimal filter that can overcome many of the problems that can affect classical approaches, such as light reflection and subject's movements, at a fraction of the training cost of deep learning approaches. Following the usual procedures for region of interest extraction and tracking, robust skin color estimation and signal pre-processing, we introduce a least-squares error optimal filter, learnt using an established training dataset to estimate the photoplethysmographic (PPG) signal more accurately from the measured color changes over time. This method not only improves the accuracy of heart rate measurement but also resulted in the extraction of a cleaner pulse signal, which could be integrated into many other useful applications such as human biometric recognition or recognition of emotional state. The method was tested on the DEAP dataset and showed improved performance over the best previous classical method on that dataset. The results obtained show that our proposed contact-free heart rate measurement method has significantly improved on existing methods.

Reliability of the BodyGuard2 (FirstBeat) in the Detection of Heart Rate Variability

There has been an increasing interest in using cardiac indicators of self-regulation in developmental science. Many researchers are interested in unobtrusive mobile devises that are able to collect reliable cardiac data outside of the laboratory setting. Although numerous new ambulatory devices have become available over the last decade, testing these devices on children in comparison to industry gold-standard devices is rarely conducted. The current study evaluated the reliability of one of these ambulatory systems, the BodyGuard2 (FirstBeat), relative to gold-standard laboratory electrocardiogram (Biopac MP150), during active and resting conditions in 4- to 6-year-old children. The BodyGuard2 performed and produced highly similar indices of heart rate variability across resting and active conditions.

Do Domestic Pigs Acquire a Positive Perception of Humans through Observational Social Learning?

Farm animals can perceive humans positively by observing another animal being positively handled. This study evaluated whether pigs acquire a positive perception of humans after observing either a high or low socially ranked conspecific receiving gentle handling. Seventy-five 21-week-old pigs were housed in 15 nursery pens (five pigs/pen) and randomly assigned to one of three pen treatments: Dominant Demonstrator Group (DDG), Subordinate Demonstrator Group (SDG) and Control Group (CG). Pigs from DDG and SDG observed a high and low socially ranked conspecific ("demonstrator"), respectively, while the demonstrator received gentle stroking and a sucrose solution for 10 min, twice a day for 5 weeks. Control group pigs received minimal human contact. Following treatment, the behavior and heart rate variability of non-demonstrator pigs were evaluated in response to a stockperson in an open-field test. Pigs from the DDG and SDG contacted the stockperson sooner (p < 0.001), spent more time investigating the stockperson (p < 0.05), accepted more stroking (p < 0.001) and exhibited a lower low/high frequency ratio (p = 0.015) compared to the CG. No differences in learning between the pigs from the DDG and SDG were found. These results suggest that pigs can learn to perceive humans positively through observational social learning, regardless of the demonstrator conspecific's social rank.

Effects of Olfactory and Auditory Enrichment on Heart Rate Variability in Shelter Dogs

Simple Summary

Many pet dogs end up in shelters, and the unpredictable and overstimulating environment can lead to high arousal and stress levels. This may manifest in behavioural problems, and decreased welfare and adoption chances. Heart rate variability is a non-invasive method to measure autonomic nervous system activity, which plays an important role in the stress response. The sympathetic nervous system is responsible for increasing the dog’s arousal in response to stress and the parasympathetic nervous system is responsible for counteracting the arousal and calming the dog. Environmental enrichment can help dogs to be more relaxed, which is likely to be reflected by increased parasympathetic activity. Dogs’ heart rate variability responses to three enrichment methods capable of reducing stress—music, lavender and a calming pheromone produced by dogs, dog appeasing pheromone and a control condition (no stimuli applied) were compared. Exposure to music appeared to activate both branches of the autonomic nervous system, as dogs in that group had higher heart rate variability parameters reflecting both parasympathetic and sympathetic activity compared to the lavender and control groups. We conclude that music may be a useful type of enrichment to relieve both the stress and boredom in shelter environments.

Abstract

Animal shelters can be stressful environments and time in care may affect individual dogs in negative ways, so it is important to try to reduce stress and arousal levels to improve welfare and chance of adoption. A key element of the stress response is the activation of the autonomic nervous system (ANS), and a non-invasive tool to measure this activity is heart rate variability (HRV). Physiologically, stress and arousal result in the production of corticosteroids, increased heart rate and decreased HRV. Environmental enrichment can help to reduce arousal related behaviours in dogs and this study focused on sensory environmental enrichment using olfactory and auditory stimuli with shelter dogs. The aim was to determine if these stimuli have a physiological effect on dogs and if this could be detected through HRV. Sixty dogs were allocated to one of three stimuli groups: lavender, dog appeasing pheromone and music or a control group, and usable heart rate variability data were obtained from 34 dogs. Stimuli were applied for 3 h a day on five consecutive days, with HRV recorded for 4 h (treatment period + 1 h post-treatment) on the 5th and last day of exposure to the stimuli by a Polar^® heart rate monitor attached to the dog’s chest. HRV results suggest that music activates both branches of the ANS, which may be useful to relieve both the stress and boredom in shelter environments.

Reactive stress-coping styles show more variable reproductive expenditure and fitness outcomes

Stress-coping styles dictate how individuals react to stimuli and can be measured by the integrative physiological parameter of resting heart-rate variability (HRV); low resting HRV indicating proactive coping styles, while high resting HRV typifies reactive individuals. Over 5 successive breeding seasons we measured resting HRV of 57 lactating grey seals. Mothers showed consistent individual differences in resting HRV across years. We asked whether proactive and reactive mothers differed in their patterns of maternal expenditure and short-term fitness outcomes within seasons, using maternal daily mass loss rate to indicate expenditure, and pup daily mass gain to indicate within season fitness outcomes. We found no difference in average rates of maternal daily mass loss or pup daily mass gain between proactive and reactive mothers. However, reactive mothers deviated more from the sample mean for maternal daily mass and pup daily mass gain than proactive mothers. Thus, while proactive mothers exhibit average expenditure strategies with average outcomes, expenditure varies much more among reactive mothers with more variable outcomes. Overall, however, mean fitness was equal across coping styles, providing a mechanism for maintaining coping style diversity within populations. Variability in reactive mothers’ expenditures and success is likely a product of their attempts to match phenotype to prevailing environmental conditions, achieved with varying degrees of success.

Coping styles in capital breeders modulate behavioural trade-offs in time allocation: assessing fine-scale activity budgets in lactating grey seals (Halichoerus grypus) using accelerometry and heart rate variability

Abstract

Balancing time allocation among competing behaviours is an essential part of energy management for all animals. However, trade-offs in time allocation may vary according to the sex of the individual, their age, and even underlying physiology. During reproduction, higher energetic demands and constrained internal resources place greater demand on optimizing these trade-offs insofar that small adjustments in time-activity may lead to substantial effects on an individual’s limited energy budget. The most extreme case is found in animals that undergo capital breeding, where individuals fast for the duration of each reproductive episode. We investigated potential underlying drivers of time-activity and describe aspects of trade-offs in time-activity in a wild, capital breeding pinniped, the grey seal Halichoerus grypus, during the lactation period. For the first time, we were able to access full 24-h activity budgets across the core duration of lactation as well as characterize how aspects of stress-coping styles influence time allocation through the use of animal-borne accelerometers and heart rate monitors in situ. We found that there was a distinct trade-off in time activity between time spent Resting and Alert (vigilance). This trade-off varied with the pup’s development, date, and maternal stress-coping style as indicated by a measure of heart rate variability, rMSSD. In contrast, time spent Presenting/Nursing did not vary across the duration of lactation given the variables tested. We suggest that while mothers balance time spent conserving resources (Resting) against time expending energy (Alert), they are also influenced by the inherent physiological drivers of stress-coping styles.

Significance statement

How animals apportion their time among different behaviours is key to their success. These trade-offs should be finely balanced to avoid unnecessary energy expenditure. Here, we examine how grey seal mothers balance their activity patterns during the short, but energetically demanding, period of pup-rearing. Animal-borne accelerometers provided a uniquely detailed and continuous record of activity during pup-rearing for 38 mothers. We also used heart rate monitors to provide measures of each individual’s stress-coping style. We found that mothers balance time Resting against remaining Alert while time Presenting/Nursing was largely independent of all factors measured. Stress-coping styles were found to drive the balancing and variation of all behaviours. This novel indication that differences in personality-like traits may drive whole activity budgets should be considered when assessing trade-offs in time allocation across a much wider variety of species.

Modelling and Validation of Computer Vision Techniques to Assess Heart Rate, Eye Temperature, Ear-Base Temperature and Respiration Rate in Cattle

Simple Summary

Animal monitoring normally requires procedures that are time- and labour-consuming. The implementation of novel non-invasive technologies could be a good approach to monitor animal health and welfare. This study aimed to evaluate the use of images and computer-based methods to track specific features of the face and to assess temperature; respiration rate and heart rate in cattle. The measurements were compared with measures obtained with conventional methods during the same time period. The data were collected from ten dairy cows that were recorded during six handling procedures across two consecutive days. The results from this study show over 92% of accuracy from the computer algorithm that was developed to track the areas selected on the videos collected. In addition, acceptable correlation was observed between the temperature calculated from thermal infrared images and temperature collected using intravaginal loggers. Moreover, there was acceptable correlation between the respiration rate calculated from infrared videos and from visual observation. Furthermore, a low to high relationship was found between the heart rate obtained from videos and from attached monitors. The study also showed that both the position of the cameras and the area analysed on the images are very important, as both had large impact on the accuracy of the methods. The positive outcomes and the limitations observed in this study suggest the need for further research

Abstract

Precision livestock farming has emerged with the aim of providing detailed information to detect and reduce problems related to animal management. This study aimed to develop and validate computer vision techniques to track required features of cattle face and to remotely assess eye temperature, ear-base temperature, respiration rate, and heart rate in cattle. Ten dairy cows were recorded during six handling procedures across two consecutive days using thermal infrared cameras and RGB (red, green, blue) video cameras. Simultaneously, core body temperature, respiration rate and heart rate were measured using more conventional ‘invasive’ methods to be compared with the data obtained with the proposed algorithms. The feature tracking algorithm, developed to improve image processing, showed an accuracy between 92% and 95% when tracking different areas of the face of cows. The results of this study also show correlation coefficients up to 0.99 between temperature measures obtained invasively and those obtained remotely, with the highest values achieved when the analysis was performed within individual cows. In the case of respiration rate, a positive correlation (r = 0.87) was found between visual observations and the analysis of non-radiometric infrared videos. Low to high correlation coefficients were found between the heart rates (0.09–0.99) obtained from attached monitors and from the proposed method. Furthermore, camera location and the area analysed appear to have a relevant impact on the performance of the proposed techniques. This study shows positive outcomes from the proposed computer vision techniques when measuring physiological parameters. Further research is needed to automate and improve these techniques to measure physiological changes in farm animals considering their individual characteristics.

Nonlinear analysis of heart rate variability for evaluating the growing pig stress response to an acute heat episode

Heart rate variability (HRV) is a proxy measure of autonomic function and can be used as an indicator of swine stress. While traditional linear measures are used to distinguish between stressed and unstressed treatments, inclusion of nonlinear HRV measures that evaluate data structure and organization shows promise for improving HRV interpretation. The objective of this study was to evaluate the inclusion of nonlinear HRV measures in response to an acute heat episode. Twenty 12- to 14-week-old growing pigs were individually housed for 7 days and acclimated to thermoneutral conditions (20.35°C ± 0.01°C; 67.6% ± 0.2% RH) before undergoing one of the two treatments: (1) thermoneutral control (TN; n = 10 pigs) or (2) acute heat stress (HS; n = 10 pigs; 32.6°C ± 0.1°C; 26.2% ± 0.1% RH). In Phase 1 of the experimental procedure (P1; 60 min), pigs underwent a baseline HRV measurement period in thermoneutral conditions before treatment [Phase 2; P2; 60 min once gastrointestinal temperature (Tg) reached 40.6°C], where HS pigs were exposed to heated conditions and TN pigs remained in thermoneutral conditions. After P2, all pigs were moved back to thermoneutral conditions (Phase 3; P3; 60 min). During each phase, Tg data were collected every 5 min and behavioural data were collected to evaluate the amount of time each pig spent in an active posture. Additionally, linear (time and frequency domain) and nonlinear [sample entropy (SampEn), de-trended fluctuation analysis, percentage recurrence, percentage determinism (%DET), mean diagonal line length in a recurrence plot] HRV measures were quantified. Heat stressed pigs exhibited greater Tg (P = 0.002) and spent less time in an active posture compared to TN pigs during P2 (P = 0.0003). Additionally, low frequency to high frequency ratio was greater in HS pigs during P3 compared to TN pigs (P = 0.02). SampEn was reduced in HS pigs during P2 (P = 0.01) and P3 (P = 0.03) compared to TN pigs. Heat stressed pigs exhibited greater %DET during P3 (P = 0.03) and tended to have greater %DET (P = 0.09) during P2 than TN pigs. No differences between treatments were detected for the remaining HRV measures. In conclusion, linear HRV measures were largely unchanged during P2. However, changes to SampEn and %DET suggest increased heat stress as a result of the acute heat episode. Future work should continue to evaluate the benefits of including nonlinear HRV measures in HRV analysis of swine heat stress.

Short communication: Assessment of disbudding pain in dairy calves using nonlinear measures of heart rate variability

The purpose of this study was to evaluate whether pain-related stress caused by disbudding could be detected using nonlinear measures of heart rate variability (HRV). Twenty-five female Holstein calves (4-7 wk of age) were randomly assigned to 1 of 3 treatments: (1) sham disbud (SHAM; n = 9), (2) disbud with lidocaine-meloxicam pain mitigation (MED; n = 8), or (3) disbud without pain mitigation (NoMED; n = 8). Heart rate variability (sample entropy, percentage determinism, percentage recurrence, or mean length of diagonal lines in a recurrence plot) was recorded on d -1, 0, 1, 3, and 5 relative to the experimental procedure, with disbudding taking place on d 0. The short-term detrended fluctuation analysis scaling exponent was greater in MED calves than in SHAM calves, indicating a greater stress response to the disbudding procedure regardless of pain mitigation. These results indicate that calves in the MED group may have experienced pain-related stress as a result of the disbudding procedure. The remaining nonlinear HRV measures did not differ by treatment. Future research on this topic should address additional potential confounding factors, such as the effect of pain-mitigating drugs on autonomic function or the influence of the autonomic nervous system on wound healing, that may prohibit HRV measurement as an indicator of disbudding pain severity.

Can heart rate variability parameters derived by a heart rate monitor differentiate between atrial fibrillation and sinus rhythm?

BACKGROUND

Heart rate variability (HRV) parameters, and especially RMSSD (root mean squared successive differences in RR interval), could distinguish atrial fibrillation (AF) from sinus rhythm(SR) in horses, as was demonstrated in a previous study. If heart rate monitors (HRM) automatically calculating RMSSD could also distinguish AF from SR, they would be useful for the monitoring of AF recurrence. The objective of the study was to assess whether RMSSD values obtained from a HRM can differentiate AF from SR in horses. Furthermore, the impact of artifact correction algorithms, integrated in the analyses software for HRV analyses was evaluated. Fourteen horses presented for AF treatment were simultaneously equipped with a HRM and an electrocardiogram (ECG). A two-minute recording at rest, walk and trot, before and after cardioversion, was obtained. RR intervals used were those determined automatically by the HRM and by the equine ECG analysis software, and those obtained after manual correction of QRS detection within the ECG software. RMSSD was calculated by the HRM software and by dedicated HRV software, using six different artifact filters. Statistical analysis was performed using the Wilcoxon signed-rank test and receiver operating curves.

RESULTS

The HRM, which applies a low level filter, produced high area under the curve (AUC) (> 0.9) and cut off values with high sensitivity and specificity. Similar results were obtained for the ECG, when low level artifact filtering was applied. When no artifact correction was used during trotting, an important decrease in AUC (0.75) occurred.

CONCLUSION

In horses treated for AF, HRMs with automatic RMSSD calculations distinguish between AF and SR. Such devices might be a useful aid to monitor for AF recurrence in horses.

Effect of Floor Cooling on Behavior and Heart Rate of Late Lactation Sows Under Acute Heat Stress

Much U.S. swine production is in Köppen climate types classified as "hot-summer humid continental" and "humid subtropical." As a result, farrowing sows are often exposed to temperatures above their upper critical temperature. This heat stress (HS) can affect sow welfare and productivity and have a negative economic impact. The study objective was to evaluate the impact of a cooling pad on sows' behavioral and heart rate responses to acute HS. Treatments were randomly allotted to ten multiparous sows to receive a constant cool water flow of 0.00 (CONTROL, n = 4), 0.25 (LOW, n = 2), 0.55 (MEDIUM, n = 2), or 0.85 (HIGH, n = 2) L/min for 100 min and replicated eight times, switching treatments so that each sow was exposed to each treatment. The cooling was initiated 1 h after the room reached 35°C for 100 min. Eating, drinking and nursing behaviors, postures, and heart rate were recorded before heating (Period 1), prior to cooling (Period 2), and during cooling (Period 3). There were no differences between LOW, MEDIUM, and HIGH flow rates for any periods on all behavioral and heart rate traits, so data were pooled (COOLED). There were no differences in any of the measures during Periods 1 and 2, except for the ratio of short term to long term heart rate variability (SD1:SD2) with higher values for CONTROL than COOLED sows in Period 2. During Period 3, CONTROL sows changed postures more frequently (11.5 ±1.6 vs. 5.1 ±1.6 changes per hour), spent more time drinker-pressing/drinking (4.4 ± 0.5 vs. 1.4 ± 0.4% of time), standing (6.6 ± 1.7 vs. 3.8 ± 1.6% of time), sitting (10.0 ± 1.2 vs. 4.0 ± 1.1), less time lying (83.0 ±1.8 vs. 92.0 ±1.7% of time), especially lying laterally (62.0 ± 5.6 vs. 75.0 ± 5.3% of time), than sows in all three cooling treatments (all P < 0.001). Heart rate during Period 3 was lower for COOLED sows compared to the CONTROL sows (100.2 ± 3.4 vs. 119.0 ± 4.0 beat per min, P < 0.001). Sows response to increased thermal load can be effectively reduced using water-cooled cooling pads, thereby improving sow comfort and welfare. The beneficial effects on behavior are noticeable from the lowest flow rate.

Recording Heart Rate Variability of Dairy Cows to the Cloud-Why Smartphones Provide Smart Solutions

In the last decades, there has been an increasing interest in animal protection and welfare issues. Heart rate variability (HRV) measurement with portable heart rate monitors on cows has established itself as a suitable method for assessing physiological states. However, more forward-looking technologies, already successfully applied to evaluate HRV data, are pushing the market. This study examines the validity and usability of collecting HRV data by exchanging the Polar watch V800 as a receiving unit of the data compared to a custom smartphone application on cows. Therefore, both receivers tap one signal sent by the Polar H7 transmitter simultaneously. Furthermore, there is a lack of suitable methods for the preparation and calculation of HRV parameters, especially for livestock. A method is presented for calculating more robust time domain HRV parameters via median formation. The comparisons of the respective simultaneous recordings were conducted after artifact correction for time domain HRV parameters. High correlations (r = 0.82⁻0.98) for cows as well as for control data set in human being (r = 0.98⁻0.99) were found. The utilization of smart devices and the robust method to determine time domain HRV parameters may be suitable to generate valid HRV data on cows in field-based settings.

Agreement between Electrocardiogram and Heart Rate Meter Is Low for the Measurement of Heart Rate Variability during Exercise in Young Endurance Horses

Analysis of the heart rate variability (HRV) gains more and more importance in the assessment of training practice and welfare in equine industry. It relies on mathematical analyses of reliably and accurately measured variations in successive inter-beat intervals, measured as RR intervals. Nowadays, the RR intervals can be obtained through two different techniques: a heart rate meter (HRM) or an electrocardiogram (ECG). The agreement and reliability of these devices has not been fully assessed, especially for recordings during exercise. The purpose of this study was to assess the agreement of two commercially available devices using the two mentioned techniques (HRM vs ECG) for HRV analysis during a standardized exercise test. Simultaneous recordings obtained during light exercise and during canter with both devices were available for 36 horses. Data were compared using a Bland–Altman analysis and the Lin’s coefficient. The agreement between the assessed HRV measures from the data obtained from the ECG and HRM was acceptable only for the mean RR interval and the mean heart rate. For the other studied measures (SDNN, root mean square of successive differences, SD1, SD2, low frequency, high frequency), the agreement between the devices was too poor for them to be considered as interchangeable in these recording conditions. The agreement tended also to be worse when speed of the exercise increased. Therefore, it is necessary to be careful when interpreting and comparing results of HRV analysis during exercise, as the results will depend upon recording devices. Furthermore, corrections and data processing included in the software of the devices affect largely the output used in the subsequent HRV analysis; this must be considered in the choice of the device.

Physiological response to an experimental 100 m flying pace race in Icelandic horses and effect of rider

This study evaluated the physiological response to an experimental 100 m flying pace race (EPR) in Icelandic horses with pace-competition experience, and whether there was an effect of rider. A cross-over design with nine horses and two riders was used. The EPR was performed twice (once with each rider) with four days of rest in-between. The EPR consisted of two runs (I and II), of which at least 100 m was in pace at full speed according to international competition rules. Plasma lactate concentration increased and was greater after pace run II than I (18.5±1.3 vs 11.9±0.7 mmol/l; P<0.001). Heart rate was higher during pace run I than II (207±3 vs 205±3; P=0.02). Heart rate and Lact had not recovered 30 min post exercise but Hct was back to resting level after 30 min recovery. Speed did not differ between riders and pace runs (pooled mean ± standard deviation of pace runs: 10.4±0.7 m/s, range 9.2-12.1 m/s) but HR and Lact were higher from warm-up and until 30 min recovery with rider 1 than 2 (P<0.001). There was a negative correlation between post EPR Lact with rider 1 and previous best record (r2=0.72, P=0.032). To conclude, a 100 m flying pace race in the Icelandic horse is a high-intensity exercise and anaerobic metabolism is crucial for performance. The rider had an effect on the physiological response but it is unclear if it was due to body weight, riding style or both. The practical relevance of the differences observed between riders remains to be proven but our results indicate that they may have limited impact on single day competitions since the speed was the same with the two riders.

Testing the feasibility of using a conveyor belt to load weanling and nursery pigs for transportation

Transportation is known to be a multi-faceted stressor, with the process of loading being one of the most significant factors impacting the stress to which animals are exposed. This project was designed to determine if using a conveyor to load pigs into the top deck of a simulated straight deck trailer could lower the stress to which pigs and handlers are exposed. Pigs were assigned to either a Control group that were herded up a stationary conveyor ramp into a top deck trailer (2.5 m above the ground); or Conveyor group which were herded onto a mobile conveyor into a top deck trailer. The conveyor was 7.6 m long, 0.9 m wide and rose to 2.5 m high at a 16° slope, and moved 11.3 m/min. Two age groups were tested; Weanling pigs which were moved in groups of 20 (n = 14 groups/treatment) and Nursery pigs which were moved in groups of 10 (n = 15 groups/treatment). Behavior was recorded during loading, including slips and falls, vocalizations, assists, and time to load. Heart rate of 2 sentinel pigs/group and the handler were recorded during loading, and body temperature of the handler after loading. Pigs were held in the simulated trailer for 30 min while heart rate was recorded. After which, they were unloaded and held in a holding pen for an additional 30 min while heart rate was recorded. There were no treatment differences for slips or falls (P < 0.90). Vocalizations were too few to analyze. Both Weanling (2.8 ± 0.7) and Nursery (1.6 ± 0.5) Conveyor pigs needed to be assisted onto the conveyor more than Weanling (1.2 ± 0.4) and Nursery (0.3 ± 0.1) Control pigs (P < 0.06). There was no difference in total loading time between the treatments for any age group (P < 0.15), with Weanling and Nursery pigs loading in 50 to 45 s, respectively. There were no treatment differences for heart rate variability measures (P > 0.10). However, loading increased heart rate of Nursery pigs (204.9 ± 5.7 bpm, P < 0.005), but not Weanling pigs (172.1 ± 9.0 bpm). Nursery pigs had a greater ratio of low frequency to high frequency power during loading (P < 0.02) compared to other phases of the procedure in both Control and Conveyor groups. Heart rate (93.9 ± 1.9 bpm) and body temperature (31.1 ± 0.3°C, eye temperature) of the handler was not affected by treatment (P < 0.26). Based on behavior and physiology, the pigs had similar experiences in both treatments. This study shows that it is feasible to use a conveyor to load pigs, but it may not be advantageous.

Context Specificity of the ANS Stress Response during Two Regrouping Experiments in Goats

The aim of this study was to analyze whether the activity of the autonomic nervous system (ANS) differs between two regrouping procedures in goats, which would indicate stimulus specificity of these stressors. Applying two regrouping procedures, we evaluated heart rate and heart rate variability (RMSSD, SDNN, and RMSSD/SDNN). The two regrouping procedures were (1) introduction of individual goats into established groups (“introduction experiment”) and (2) temporary separation and subsequent reintegration of individuals from/into their group with two levels of contact during separation (“separation experiment”). In the “introduction experiment,” the heart rate of introduced goats while lying decreased continuously from an average 78 to 68 beats/min from before the introduction to the last day of the introduction period. Inversely, RMSSD increased continuously from 41 to 62 ms, which, on its own, would indicate an adaptation to the situation. During the “separation experiment,” heart rate while lying was higher when goats were separated in the “acoustic contact treatment” (82 beats/min on average) compared with the “restricted physical contact treatment” (75 beats/min on average). This difference reflected a higher level of arousal during the “acoustic contact treatment.” However, heart rate activity did not allow detecting effects of separation or reintegration. Even though it can be assumed that both the separation and introduction of goats are stressful for goats, the ANS reactions observed in this study differed between the two management procedures indicating that the ANS activation was specific to each situation. In addition, we discuss the ANS results in context with earlier findings of variables of the hypothalamic pituitary adrenal (HPA) axis (fecal cortisol metabolites) and behavior (lying and feeding). As correspondence between ANS, HPA, and behavioral reactions was limited both within and across experiments, the results of this study underline the concept that stress response patterns are context specific.

Hypothalamic-pituitary-adrenal and cardiac autonomic responses to transrectal examination differ with behavioral reactivity in dairy cows

Behavior, hypothalamic-pituitary-adrenal axis, and cardiac autonomic nervous system (ANS) activity were evaluated in response to transrectal examination in nonlactating Holstein-Friesian cows with different behavioral reactivity. According to behavioral reactions shown to the procedure of fixing the heart rate (HR) monitors, the 20 cows with the highest and the 20 cows with the lowest behavioral reactivity were involved in the study (high responder, n=20; and low responder, n=20, respectively). Activity of the ANS was assessed by HR and HR variability parameters. Blood and saliva were collected at 5 min before (baseline) and 0, 5 10, 15, 20, 30, 40, 60, and 120 min after the examination to determine cortisol concentrations. The examination lasted for 5 min. Cardiac parameters included HR, the root mean square of successive differences between the consecutive interbeat intervals, the high frequency (HF) component of heart rate variability, and the ratio between the low frequency (LF) and HF parameter (LF/HF). Following the examination, peak plasma and saliva cortisol levels and the amplitude of the plasma and saliva cortisol response were higher in high responder cows than in low responders. Areas under the plasma and saliva cortisol response curves were greater in high responder cows. Plasma and salivary cortisol levels correlated significantly at baseline (r=0.91), right after examination (r=0.98), and at peak levels (r=0.96). Area under the HR response curve was higher in low responder cows; however, maximum HR and the amplitude of the HR response showed no differences between groups. Minimum values of both parameters calculated for the examination were higher in high responders. Following the examination, response parameters of root mean square of successive differences and HF did not differ between groups. The maximum and the amplitude of LF/HF response and area under the LF/HF response curve were lower in low responder cows, suggesting a lower sympathetic activation of the ANS. Although changes in behaviors indicated that the procedure was painful for the animals, no differences were observed either in vocalization or in attendant behavior between groups during the examination. Our results demonstrate that behaviorally more reactive animals exhibit increased plasma and salivary cortisol concentrations and higher cardiac autonomic responsiveness to transrectal examination than less reactive cows. Salivary cortisol may substitute for plasma cortisol when assessing response of cattle to stress.

Algorithm-supported visual error correction (AVEC) of heart rate measurements in dogs, Canis lupus familiaris

Dog heart rate (HR) is characterized by a respiratory sinus arrhythmia, and therefore makes an automatic algorithm for error correction of HR measurements hard to apply. Here, we present a new method of error correction for HR data collected with the Polar system, including (1) visual inspection of the data, (2) a standardized way to decide with the aid of an algorithm whether or not a value is an outlier (i.e., “error”), and (3) the subsequent removal of this error from the data set. We applied our new error correction method to the HR data of 24 dogs and compared the uncorrected and corrected data, as well as the algorithm-supported visual error correction (AVEC) with the Polar error correction. The results showed that fewer values were identified as errors after AVEC than after the Polar error correction (p < .001). After AVEC, the HR standard deviation and variability (HRV; i.e., RMSSD, pNN50, and SDNN) were significantly greater than after correction by the Polar tool (all p < .001). Furthermore, the HR data strings with deleted values seemed to be closer to the original data than were those with inserted means. We concluded that our method of error correction is more suitable for dog HR and HR variability than is the customized Polar error correction, especially because AVEC decreases the likelihood of Type I errors, preserves the natural variability in HR, and does not lead to a time shift in the data.

Physiological and Behavioral Responses of Horses to Wither Scratching and Patting the Neck When Under Saddle

Riding is considered to be an arousing activity for horses. It has been suggested that wither scratching may be a more useful tool for relaxation compared with the common practice of neck patting. In the current study, 18 horses were exposed to 3 treatments, including control or no interaction, neck patting, and wither scratching, for 1 min each following a short obstacle course. Heart rate, heart rate variability, and a variety of behaviors were measured in the horses. Wither scratching produced a significantly longer duration of relaxed-type behaviors. Wither scratching could be a useful tool to help a horse relax while under saddle. Additionally, the study identified 2 ear positions that may be useful for future research in horse behavior.

Behavioural and physiological measures indicate subtle variations in the emotional valence of young pigs

In the study of animal emotions, emotional valence has been found to be difficult to measure. Many studies of farm animals' emotions have therefore focussed on the identification of indicators of strong, mainly negative, emotions. However, subtle variations in emotional valence, such as those caused by rather moderate differences in husbandry conditions, may also affect animals' mood and welfare when such variations occur consistently. In this study, we investigated whether repeated moderate aversive or rewarding events could lead to measurable differences in emotional valence in young, weaned pigs. We conditioned 105 female pigs in a test arena to either a repeated startling procedure (sudden noises or appearances of objects) or a repeated rewarding procedure (applesauce, toy and straw) over 11 sessions. Control pigs were also regularly exposed to the same test arena but without conditioning. Before and after conditioning, we measured heart rate and its variability as well as the behavioural reactions of the subjects in the test arena, with a special focus on detailed acoustic analyses of their vocalisations. The behavioural and heart rate measures were analysed as changes compared to the baseline values before conditioning. A limited number of the putative indicators of emotional valence were affected by the conditioning. We found that the negatively conditioned pigs showed changes that were significantly different from those in control pigs, namely a decrease in locomotion and an increase in standing. The positively conditioned pigs, however, showed a stronger increase in heart rate and a smaller decrease in SDNN (a heart rate variability parameter indicating changes in autonomic regulation) compared to the controls. Compared to the negatively conditioned pigs, the positively conditioned pigs produced fewer vocalisations overall as well as fewer low-frequency grunts but more high-frequency grunts. The low-frequency grunts of the negatively conditioned pigs also showed lower frequency parameters (bandwidth, maximum frequency, 25% and 50% quartiles) compared to those of the positively conditioned pigs. In any of the statistically significant results, the conditioning accounted for 1.5-11.9% of variability in the outcome variable. Hence, we conclude that repeated moderate aversive and rewarding events have weak but measurable effects on some aspects of behaviour and physiology in young pigs, possibly indicating changes in emotional valence, which could ultimately affect their welfare. The combination of ethophysiological indicators, i.e., the concurrent examination of heart rate measures, behavioural responses and especially vocalisation patterns, as used in the current study, might be a useful way of examining subtle effects on emotional valence in further studies.

Surgical implantation and functional assessment of an invasive telemetric system to measure autonomic responses in domestic pigs

The first aim of this study was to establish a surgical procedure to implant a new telemetric device for the continuous recording of electrocardiogram (ECG) and blood pressure (BP) in freely moving pigs. A second aim was the functional assessment of cardiovascular parameters, including heart rate variability (HRV) and blood pressure variability (BPV), so that these data could be used as the basis for the objective evaluation of autonomic activity and balance in different behavioural contexts. Eleven domestic pigs (German Landrace) underwent surgery for the placement of a telemetric device. At day 15 after surgery, 512 consecutive inter-beat intervals and pressure waves were analysed using different detection methods (automatic and manually corrected) while the animals were resting or feeding, respectively. HRV and BPV were calculated. Incomplete datasets were found in four pigs due to missing ECG or BP signals. Technical and surgical issues concerning catheterisation and detachment of the negative ECG lead were continuously improved. In the remaining pigs, excellent signal quality (manually corrected data of 1%) was obtained during resting and acceptable signal quality (<10%) was obtained during feeding. Automatic triggering was sufficiently reliable to eliminate errors in BP recordings during active behaviour, but this was not the case for ECG recordings. Sympathetic arousal with accompanying vagal withdrawal during feeding was documented. The established surgical implantation and functional assessment of the telemetric system with the reliable registration of cardiovascular parameters in freely moving pigs could serve as a basis for future studies of autonomic regulation in context of stress and animal welfare.

Cardiac autonomic activity has a circadian rhythm in summer but not in winter in non-lactating pregnant dairy cows

This investigation was conducted to examine circadian and seasonal rhythms of heart rate and heart rate variability (HRV) by means of hour-by-hour recordings over 24h in a large population of non-lactating Holstein-Friesian pregnant cows [N=56, summer (June-July); N=61, winter (November-December)]. Data were collected during a 5-day period from each animal. Besides parameters of cardiac autonomic function [the high-frequency (HF) component of HRV and the ratio between the low-frequency (LF) and the HF components (LF/HF ratio)], the RR triangular index and Lmax were calculated. A clear circadian profile was observed for every parameter in summer. Heart rate elevated gradually with the course of the day from 7:00 to 17:00 o'clock and then slightly decreased from 18:00 to 6:00. Sympathovagal balance shifted towards sympathetic dominance during the daytime (increased LF/HF ratio), whereas parasympathetic activity was predominant during the night (increased HF). Lmax reflected a chaotic behavior of heart rate fluctuations during the afternoon in summer. Decreased values of RR triangular index indicated a sensitive period for cows between 14:00 and 16:00 o'clock in summer. During winter, except for the RR triangular (RRtri) index reflecting a high overall variability in R-R intervals between 12:00 and 23:00 o'clock, heart rate and HRV showed no periodicity over the 24-h period. The results suggest an impaired cardiac autonomic function during daytime in summer. HF, Lmax and RRtri index showed seasonal differences for both daytime and nighttime. Heart rate was higher in summer than in winter during the daytime, whereas the LF/HF ratio was higher in winter during the nighttime. Circadian and seasonal rhythms of cardiovascular function are presumably related to the differing temperature, and animal activity associated with summer and winter. As all of the investigated parameters are commonly used in bovine HRV research, these findings have practical implications for behavioral, physiological and welfare studies on dairy cattle.

Anticipation and frequency of feeding affect heart reactions in domestic pigs

Measuring heart reactions has become a widely used method for the assessment of emotions. Heart rate and its variability, which can quite easily be noninvasively recorded, reflect the inputs of the sympathetic and parasympathetic branches of the autonomous nervous system. We tested the hypothesis that frequent anticipation of a positive event results in an increased state of welfare in pigs, expressed as positive arousal in anticipation of announced feeding as well as lowered heart rate and augmented heart rate variability during resting periods. We used a controlled paradigm with 3 groups of young domestic pigs (Sus scrofa domestica). We compared frequent acoustic announcement of feed delivery (group 1: 3 feedings between 0730 h and 1030 h plus 3 feedings between 1200 h and 1530 h) with the same number of feedings as in group 1 but without a temporal relation to the sound (group 2) and with a fixed-schedule feeding (group 3: 2 feedings at 0600 h and 1500 h). Specific cardiac and behavioral reactions indicated short-term (1 min) anticipation in the conditioned group. In this group, heart rate increased (P < 0.001) mainly through vagal withdraw and behavior became more active (P < 0.001). Only the conditioned group displayed changing heart rate characteristics during the sound. Pigs in the frequent unpredictable feed group reacted to feed delivery with increased heart rates (P < 0.001), whereas the heart-rate characteristics of pigs with the fixed schedule were unchanged during the sound and while the other 2 treatment groups were feeding. Clear evidence for long-term anticipation (over the course of hours) was not present in the data. Comparisons between the 3 treatment groups suggested that in housing conditions where pigs cannot obtain feed by their actions but must wait for feed delivery, feeding at 2 fixed times would be preferred. Animals in this treatment group presented lower resting heart rates at the end of the experiment than animals in the other 2 groups (P < 0.01). Therefore, merely announcing a positive stimulus without giving control to its access is apparently not suitable for increasing welfare.

Heart Rate and Heart Rate Variability in Dairy Cows with Different Temperament and Behavioural Reactivity to Humans

From the 1990s, extensive research was started on the physiological aspects of individual traits in animals. Previous research has established two extreme (proactive and reactive) coping styles in several animal species, but the means of reactivity with the autonomic nervous system (ANS) activity has not yet been investigated in cattle. The aim of this study was the characterization of cardiac autonomic activity under different conditions in cows with different individual characteristics. For this purpose, we investigated heart rate and ANS-related heart rate variability (HRV) parameters of dairy cows (N = 282) on smaller- and larger-scale farms grouped by (1) temperament and (2) behavioural reactivity to humans (BRH). Animals with high BRH scores were defined as impulsive, while animals with low BRH scores were defined as reserved. Cardiac parameters were calculated for undisturbed lying (baseline) and for milking bouts, the latter with the presence of an unfamiliar person (stressful situation). Sympathetic tone was higher, while vagal activity was lower in temperamental cows than in calm animals during rest both on smaller- and larger-scale farms. During milking, HRV parameters were indicative of a higher sympathetic and a lower vagal activity of temperamental cows as compared to calm ones in farms of both sizes. Basal heart rate did not differ between BRH groups either on smaller- or larger-scale farms. Differences between basal ANS activity of impulsive and reserved cows reflected a higher resting vagal and lower sympathetic activity of reserved animals compared to impulsive ones both on smaller- and larger-scale farms. There was no difference either in heart rate or in HRV parameters between groups during milking neither in smaller- nor in larger-scale farms. These two groupings allowed to draw possible parallels between personality and cardiac autonomic activity during both rest and milking in dairy cows. Heart rate and HRV seem to be useful for characterisation of physiological differences related to temperament and BRH.

Heart Rate Variability as an Indicator of Chronic Stress Caused by Lameness in Dairy Cows

Most experimental studies on animal stress physiology have focused on acute stress, while chronic stress, which is also encountered in intensive dairy cattle farming–e.g. in case of lameness–, has received little attention. We investigated heart rate (HR) and heart rate variability (HRV) as indicators of the autonomic nervous system activity and fecal glucocorticoid concentrations as the indicator of the hypothalamic–pituitary–adrenal axis activity in lame (with locomotion scores 4 and 5; n = 51) and non-lame (with locomotion scores 1 and 2; n = 52) Holstein-Friesian cows. Data recorded during the periods of undisturbed lying–representing baseline cardiac activity–were involved in the analysis. Besides linear analysis methods of the cardiac inter-beat interval (time-domain geometric, frequency domain and Poincaré analyses) non-linear HRV parameters were also evaluated. With the exception of standard deviation 1 (SD1), all HRV indices were affected by lameness. Heart rate was lower in lame cows than in non-lame ones. Vagal tone parameters were higher in lame cows than in non-lame animals, while indices of the sympathovagal balance reflected on a decreased sympathetic activity in lame cows. All geometric and non-linear HRV measures were lower in lame cows compared to non-lame ones suggesting that chronic stress influenced linear and non-linear characteristics of cardiac function. Lameness had no effect on fecal glucocorticoid concentrations. Our results demonstrate that HRV analysis is a reliable method in the assessment of chronic stress, however, it requires further studies to fully understand the elevated parasympathetic and decreased sympathetic tone in lame animals.