J. N. Marchant-Forde

Heart rate variability as a measure of autonomic regulation of cardiac activity for assessing stress and welfare in farm animals : A review

Measurement of heart rate variability (HRV) is a non-invasive technique that can be used to investigate the functioning of the autonomic nervous system, especially the balance between sympathetic and vagal activity. It has been proven to be very useful in humans for both research and clinical studies concerned with cardiovascular diseases, diabetic autonomic dysfunction, hypertension and psychiatric and psychological disorders. Over the past decade, HRV has been used increasingly in animal research to analyse changes in sympathovagal balance related to diseases, psychological and environmental stressors or individual characteristics such as temperament and coping strategies. This paper discusses current and past HRV research in farm animals. First, it describes how cardiac activity is regulated and the relationships between HRV, sympathovagal balance and stress and animal welfare. Then it proceeds to outline the types of equipment and methodological approaches that have been adapted and developed to measure inter-beats intervals (IBI) and estimate HRV in farm animals. Finally, it discusses experiments and conclusions derived from the measurement of HRV in pigs, cattle, horses, sheep, goats and poultry. Emphasis has been placed on deriving recommendations for future research investigating HRV, including approaches for measuring and analysing IBI data. Data from earlier research demonstrate that HRV is a promising approach for evaluating stress and emotional states in animals. It has the potential to contribute much to our understanding and assessment of the underlying neurophysiological processes of stress responses and different welfare states in farm animals.

Review:Transport Losses in Market Weight Pigs: I. A Review of Definitions, Incidence, and Economic Impact

ABSTRACT Transport losses (dead and nonambulatory pigs) present animal welfare, legal, and economic challenges to the US swine industry. The objectives of this review are to explore 1) the historical perspective of transport losses; 2) the incidence and economic implications of transport losses; and 3) the symptoms and metabolic characteristics of fatigued pigs. In 1933 and 1934, the incidence of dead and nonambulatory pigs was reported to be 0.08 and 0.16%, respectively. More recently, 23 commercial field trials (n = 6,660,569 pigs) were summarized and the frequency of dead pigs, nonambulatory pigs, and total transport losses at the processing plant were 0.25, 0.44, and 0.69% respectively. In 2006, total economic losses associated with these transport losses were estimated to cost the US pork industry approximately

The welfare of pigs

46 million. Furthermore, 0.37 and 0.05% of the nonambulatory pigs were classified as either fatigued (nonambulatory, noninjured) or injured, respectively, in 18 of these trials (n = 4,966,419 pigs). Fatigued pigs display signs of acute stress (open-mouth breathing, skin discoloration, muscle tremors) and are in a metabolic state of acidosis, characterized by low blood pH and high blood lactate concentrations; however, the majority of fatigued pigs will recover with rest. Transport losses are a multifactorial problem consisting of people, pig, facility design, management, transportation, processing plant, and environmental factors, and, because of these multiple factors, continued research efforts are needed to understand how each of the factors and the relationships among factors affect the well-being of the pig during the marketing process.

Repeated intranasal oxytocin administration in early life dysregulates the HPA axis and alters social behavior

Series Preface Acknowledgements List of Contributors 1. INTRODUCTION TO THE WELFARE OF PIGS Jeremy N. Marchant-Forde 2. THE NATURAL BEHAVIOR OF THE PIG Richard B. DEath and Simon P. Turner 3. ADVANCES IN THE STUDY OF COGNITION, BEHAVIOURAL PRIORITIES AND EMOTIONS Suzanne Held, Jonathan J. Cooper and Michael T. Mendl 4. WELFARE OF DRY SOWS Jeremy N. Marchant-Forde 5. WELFARE OF PIGS IN THE FARROWING ENVIRONMENT Anna K. Johnson and Jeremy N. Marchant-Forde 6. HOUSING THE FATTENING PIG Niamh E. OConnell 7. PIGS AND HUMANS Hans A.M. Spoolder and Susanne Waiblinger 8. BALANCE BETWEEN PORCINE DISEASE AND WELFARE Wim J.A. Boersma, Jan van der Meulen and Theo A. Niewold 9. WELFARE INTO PRACTICE David C.J. Main 10. WELFARE OF PIGS DURING TRANSPORT AND SLAUGHTER Jeremy N. Marchant-Forde and Ruth M. Marchant-Forde 11. FUTURE PERSPECTIVES OF THE WELFARE OF PIGS Donald C. Lay, Jr and Jeremy N. Marchant-Forde INDEX

Effects of a “step-up” ractopamine feeding program, sex, and social rank on growth performance, hoof lesions, and Enterobacteriaceae shedding in finishing pigs1

Agonistic interactions are a powerful stressor. Conversely, positive social interactions can reduce the adverse effects of social stress. This possibly occurs through the action of oxytocin (OT), a neuropeptide able to reduce activation of the hypothalamo-pituitary-adrenal (HPA) axis. We hypothesized that repeated OT intranasal administration to neonatal pigs could provide long-lasting protective effects against social stress. In each of six litters, two pigs per litter received 0.5 mL of saline containing 24 IU (or 50 μg) of OT intranasally and two control littermates received 0.5 mL of saline as a control at 1, 2 and 3 days of age. Contrary to our predictions, when socially mixed after weaning at 17 days of age, neonatally OT-administered pigs received more aggressive interactions and performed more aggressive interactions in return, showed greater locomotion, spent less time in social contact, and had greater cortisol concentrations than control pigs. When this social mixing was repeated at 8 weeks of age, OT pigs still performed more aggressive interactions and had greater adrenocorticotropic hormone concentrations than control pigs. A dexamethasone suppression test and corticotropic releasing hormone administration challenge at 11 weeks of age revealed that OT pigs were less responsive to dexamethasone than control pigs, suggesting a deficient HPA axis negative feedback control. Postnatal repeated OT administration altered social behavior and resulted in a long-term dysregulation of the HPA axis. These findings highlight the complex, fine-tuning of the neurobiological mechanisms regulating the development of social behavior and suggest caution in the application of neonatal peptide treatments during early development.

Behavior and peripheral amine concentrations in relation to ractopamine feeding, sex, and social rank of finishing pigs.

Increasing concern for animal well-being and food safety has stimulated the investigation of feed additives such as ractopamine (RAC), a beta-agonist widely used to improve production performance of finishing pigs. The objective of this study was to determine effects of RAC feeding, delivered as a step-up program (5 mg/kg for 2 wk followed by 10 mg/kg for 2 wk), on growth performance, Enterobacteriaceae shedding, including Salmonella, and hoof lesions, also taking into account sex and social rank of pigs. A total of 64 barrows and gilts (balanced by treatment and sex) were assigned to pens of 4 (by sex) as either control (CTL) or RAC treatment. Social ranks (dominant, intermediate, and subordinate) of pigs in each pen were determined by behavioral observation during 48 h post-mixing. Fecal samples were collected once per week for 5 wk. At slaughter, the 32 dominant and subordinate barrows and gilts (16/sex) were examined for hoof lesions, and luminal contents from ileum, cecum, and rectum were collected. Pigs fed RAC had increased growth performance (P < 0.05) with social rank of animals affecting overall ADG (P < 0.05). Gilts gained more backfat than barrows when comparing to baseline values at both 10th and last ribs (P < 0.05), whereas loin eye area increased at a similar rate for both barrows and gilts (P > 0.10). No significant effect of RAC feeding was found on backfat or loin eye area (P > 0.10). At slaughter, RAC-fed pigs had greater BW (P < 0.05). Despite the positive effects of RAC feeding on growth performance, pigs fed the compound had a greater frequency of front and rear hoof lesions as did barrows and dominant individuals (P < 0.05). Detectable concentrations of Salmonella shedding were not identified at any time during the experiment. Enterobacteriaceae shedding concentrations from RAC-fed pigs peaked at the first week of feeding and progressively decreased until slaughter. At slaughter, rectal and cecal Enterobacteriaceae concentrations were less in RAC-fed pigs than in CTL pigs (P < 0.05). Social rank tended to affect gut Enterobacteriaceae populations of barrows more than in gilts (P < 0.10). The effects of RAC feeding on hoof soundness and Enterobacteriaceae populations in the gastrointestinal tract of finishing pigs warrant further investigation. It is also proposed that the integration of the social rank status of the individual into future studies should be considered, because it may affect treatment responses.

Aggressiveness and brain amine concentration in dominant and subordinate finishing pigs fed the β-adrenoreceptor agonist ractopamine.

Aggression can impair productivity and well-being. The association between aggression in finishing pigs and the feed additive ractopamine (RAC), a beta-adrenoreceptor agonist, is unknown and warrants further investigation. Our goal was to examine behavioral activity, including aggression, in the home pen and concentrations of peripheral amines in barrows and gilts, taking into account diet (RAC) and social rank. Sixty-four finishing pigs, housed in pens of 4 by sex, were fed either a control (CTL) or RAC-added (5 mg/kg for 2 wk plus 10 mg/kg for another 2 wk) diet. The top dominant and bottom subordinate pigs in each pen were determined at mixing (2 wk pretrial). The behavior of all pigs was recorded continuously during the pretrial week (baseline) and for the following 4 wk. These behavioral data were used to evaluate home pen aggression, including the number of agonistic interactions (AINX) and constituent aggressive actions, during a 3-h period (0800 to 1100 h) once per week and their change in relation to the baseline. Time-budget behaviors and postures were analyzed over eight 24-h periods (2 d/wk) using 10-min instantaneous scan sampling that focused on only the dominant and subordinate pigs in each pen. These 2 pigs were also subjected to blood collection once per week during the trial to determine concentrations of dopamine, norepinephrine, epinephrine, and serotonin (5-HT) using HPLC. Gilts performed more bites and total actions per AINX than barrows, and RAC-fed gilts increased bites and pursuits, whereas these behaviors decreased compared with baseline values in all other subgroups (P < 0.05). Gilts fed RAC increased the total number actions per AINX, whereas the occurrence of AINX decreased for all subgroups (P < 0.01). Overall, RAC-fed pigs were more behaviorally active, spending more time alert, bar biting, and sham chewing compared with CTL pigs (P < 0.05). The dominant RAC-fed pigs tended to have the greatest norepinephrine concentrations among the tested subgroups (P = 0.08). Dominant barrows had greater epinephrine concentrations than subordinate barrows (P < 0.05). The RAC-fed gilts tended to have lesser 5-HT concentrations than CTL gilts (P = 0.08), whereas concentrations were similar in barrows (P > 0.10). Greater activity and the increase in oral-related behaviors observed in RAC-fed pigs may be mediated by the increase in arousal caused by RAC. Intensified aggression in gilts, especially when fed RAC, may be linked to reduced central 5-HT and greater noradrenergic activity, and further research on brain neurotransmitters in gilts is needed.

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine

Under farm conditions, aggression related to the formation of social hierarchy and competition for resources can be a major problem because of associated injuries, social stress, and carcass losses. Any factor that may affect the regulation and amount of aggression within a farmed system, for instance, feeding the beta-adrenoreceptor agonist ractopamine (RAC), is therefore worthy of investigation. The objectives of this study were to assess the effects of the widely used swine feed additive RAC, considering also the effects of sex and social rank on aggressiveness and concentrations of brain amines, neurotransmitters essential for controlling aggression, in finishing pigs. Thirty-two barrows and 32 gilts (4 pigs/pen by sex) were fed either a control diet or a diet with RAC (Paylean, Elanco Animal Health, Greenfield, IN) added (5 mg/kg for 2 wk, followed by 10 mg/kg for 2 wk). The top dominant and bottom subordinate pigs (16 pigs/sex) in each pen were determined after mixing by a 36-h period of continuous behavioral observation. These pigs were then subjected to resident-intruder tests (maximum 300 s) during the feeding trial to measure aggressiveness. At the end of wk 4, the amygdala, frontal cortex, hypothalamus, and raphe nuclei were dissected and analyzed for concentrations of dopamine (DA); serotonin (5-HT); their metabolites 3,4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid, and 5-hydroxyindoleacetic acid (5-HIAA), respectively; norepinephrine; and epinephrine using HPLC. Ractopamine-fed gilts performed more attacks during the first 30 s of testing than pigs in all other subgroups (P < 0.05). By the end of the resident-intruder test (300 s), the dominant control gilts and barrows, and both dominant and subordinate RAC-fed gilts performed the greatest percentage of attacks (P < 0.05). Gilts had decreased norepinephrine and DOPAC concentrations in the amygdala and frontal cortex, and when fed RAC, gilts also had the least 5-HIAA concentration and greatest DA turnover rate in the amygdala (P < 0.05). The 5-HT concentration was less in the frontal cortex of gilts compared with barrows and in the raphe nuclei (single site for brain 5-HT synthesis) of dominant gilts (P < 0.05). Ractopamine may be affecting aggressive behavior through indirect action on central regulatory mechanisms such as the DA system. The aggressive pattern observed in the tested pigs, especially in gilts, is likely linked to brain monoamine profiling of a deficient serotonergic system in the raphe nuclei, amygdala, and frontal cortex, and enhanced DA metabolism in the amygdala, brain areas vital for aggression regulation.

Gene expression of serotonin and dopamine receptors and monoamine oxidase-A in the brain of dominant and subordinate pubertal domestic pigs (Sus scrofa) fed a β-adrenoreceptor agonist

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n=6) and gilts (n=4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex interaction, and day of injection, with mixed models and Tukeys post-hoc tests. The best-fit range for LF was 0.0-0.09 Hz, and HF was 0.09-2.0 Hz (r²: 0.41 and 0.43, respectively). Propranolol and saline injections led to a greater overall total power and overall higher inter-beat interval, HF and LF power. Atropine led to a dominant sympathovagal balance of the cardiac activity in pigs. In addition, atropine led to an increase in LF power of both systolic and diastolic blood pressures in gilts suggesting vagal tone mediation of BPV. The understanding of autonomic regulation of HRV and BPV in domestic swine facilitates our ability to detect and quantify stress responses, and broadens its application in assessing farm animal welfare.

The Science of Animal Behavior and Welfare: Challenges, Opportunities, and Global Perspective

Aggression is a major source of social stress with negative effects on health and well-being, yet limited information is known about the molecular mechanisms mediating aggressive behavior in swine. Ractopamine (RAC) is a β-adrenoreceptor agonist that enhances growth but increases aggressive behaviors in female pigs. Thus, the effects of RAC, sex, and social rank on the mRNA abundance of genes encoding serotonin and dopamine receptors, and monoamine oxidase (MAO)-A in brains of sub-adult pigs were evaluated. Top dominant and bottom subordinate pigs (16/sex) in pens of 4 pigs were determined, and fed either the control or RAC diets. At day 31, their raphe nuclei (RN), amygdala (AMY), frontal cortex (FC), and hypothalamus (HYP) were dissected; relative mRNA abundance for 5-HT₁(B), 5-HT₂(A), 5-HT₂(B), and D₁ receptors, and MAO-A was determined by Q-RT-PCR and data subjected to multivariate linear mixed model analysis and Tukey post-hoc test. Expression of 5-HT₁(B) and MAO-A was suppressed in the AMY of female pigs; 5-HT₂(B) expression was also suppressed in the RN, FC and HYP of females and RN of dominant pigs (P < 0.05). Expression of 5-HT₂(A) was more up-regulated in RN of females compared to males (P < 0.05). Expression of D₁ varied in RN and FC mostly as a function of RAC feeding and its interaction with sex and social rank (P < 0.05). While RAC feeding is related to changes in expression of the D1 receptor mRNA, suppression in expression of serotonergic genes detected in the brain of pigs, especially in females independent of social rank, may be mediating the inter-individual offensive aggression.