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The ability to assess emotionality is important within animal welfare research. Yet, for farm animals, few tests of emotionality have been well validated. Here we investigated the construct validity of behavioural measures of pig emotionality in an open-field test by manipulating the experiences of pigs in three ways. In Experiment One (pharmacological manipulation), pigs pre-treated with Azaperone, a drug used to reduce stress in commercial pigs, were more active, spent more time exploring and vocalised less than control pigs. In Experiment Two (social manipulation), pigs that experienced the open-field arena with a familiar companion were also more exploratory, spent less time behaviourally idle, and were less vocal than controls although to a lesser degree than in Experiment One. In Experiment Three (novelty manipulation), pigs experiencing the open field for a second time were less active, explored less and vocalised less than they had done in the first exposure to the arena. A principal component analysis was conducted on data from all three trials. The first two components could be interpreted as relating to the form (cautious to exploratory) and magnitude (low to high arousal) of the emotional response to open-field testing. Based on these dimensions, in Experiment One, Azaperone pigs appeared to be less fearful than saline-treated controls. However, in Experiment Two, exposure to the arena with a conspecific did not affect the first two dimensions but did affect a third behavioural dimension, relating to oro-nasal exploration of the arena floor. In Experiment Three, repeat exposure altered the form but not the magnitude of emotional response: pigs were less exploratory in the second test. In conclusion, behavioural measures taken from pigs in an open-field test are sensitive to manipulations of their prior experience in a manner that suggests they reflect underlying emotionality. Behavioural measures taken during open-field exposure can be useful for making assessments of both pig emotionality and of their welfare., (Copyright © 2011 Elsevier Inc. All rights reserved.)

In rodents and humans stressful events in early life e.g. maternal deprivation, can increase sensitivity to stress in later life. Humans may become more susceptible to mood disorders, e.g. depression. In livestock species, such as pigs, early weaning is a form of maternal deprivation. We investigated behavioural consequences in 99 female pigs weaned at three different ages (12, 21 and 42 days; d12, d21, d42). Pigs were habituated to an open field arena over 6 days before being given 5-min open-field tests over three subsequent days (days 77-79). Early-weaned pigs (d12) showed behavioural inhibition (reduced vocalisations and lower activity) compared with later-weaned pigs, although in all groups these measures declined over the three tests, so this treatment difference might reflect more rapid habituation to the test in d12 pigs. Long-term effects on mood-related 5-HT receptor subtypes were measured in the brain at 90 days in a random sample of the d12 (n=8) and d42 pigs (n=8), using (3)H-ligand-binding and autoradiography and in situ hybridisation histochemistry. There were no differences between weaning ages in binding of (3)H-8-OH-DPAT (5-HT(1A) receptor agonist) or of (3)H-ketanserin (5-HT(2A) receptor antagonist) to any brain region studied. In d12 pigs, 5-HT(1A) receptor mRNA expression per unit area was 29%, 63%, 52% and 64% lower than in d42 pigs in the parvocellular PVN, amygdala and hippocampal dentate gyrus and pyramidal cell layer, respectively. The ratio of expression per cell to expressing cells per unit area was also lower, by 31%, in the pars horizontalis of the PVN in d12 pigs. Conversely, 5-HT(2A) receptor mRNA was expressed at a 25% and 28% higher density per unit area in the amygdala and pyramidal cell layer of the hippocampus, respectively, in these d12 pigs. In individual pigs, across brain regions, 5-HT(1A) receptor mRNA data were 70-79% correlated with binding data but no correlation was found for 5-HT(2A) data, suggesting different regulatory mechanisms. The behavioural and neurobiological responses to early weaning might represent either dysfunction or adaptation. Further investigation is required.

Many experiments report that animals will work (lever press) for food in the presence of freely available identical food. This phenomenon has attracted the attention of applied ethologists because it seems to prove that animals have a need to express appetitive behavior. If this is the case, then it has implications for the provision of environmental enrichment for animals in captivity. In this experiment, we maintained 6 pigs in closed economy environments for three 120-hr choice periods in which they had continuous free access to operant and identical free food. In the experiment, we tested pigs using 2 different operant schedules, fixed ratio (FR) 5 and variable ratio (VR) 5. We used a VR schedule because many enrichment studies claim that unpredictability is an important characteristic that makes an enrichment device attractive. The results show that pigs exhibited a negligible level of contrafreeloading (M +/- standard error of the mean proportion = 0.05 +/- 0.01). Furthermore, there were no significant differences between FRs and VRs of reinforcement.

Infectious diseases of farmed and wild animals pose a recurrent threat to food security and human health. The macrophage, a key component of the innate immune system, is the first line of defence against many infectious agents and plays a major role in shaping the adaptive immune response. However, this phagocyte is a target and host for many pathogens. Understanding the molecular basis of interactions between macrophages and pathogens is therefore crucial for the development of effective strategies to combat important infectious diseases. We explored how porcine pluripotent stem cells (PSCs) can provide a limitless in vitro supply of genetically and experimentally tractable macrophages. Porcine PSC-derived macrophages (PSCdMs) exhibited molecular and functional characteristics of ex vivo primary macrophages and were productively infected by pig pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) and African swine fever virus (ASFV), two of the most economically important and devastating viruses in pig farming. Moreover, porcine PSCdMs were readily amenable to genetic modification by CRISPR/Cas9 gene editing applied either in parental stem cells or directly in the macrophages by lentiviral vector transduction. We show that porcine PSCdMs exhibit key macrophage characteristics, including infection by a range of commercially relevant pig pathogens. In addition, genetic engineering of PSCs and PSCdMs affords new opportunities for functional analysis of macrophage biology in an important livestock species. PSCs and differentiated derivatives should therefore represent a useful and ethical experimental platform to investigate the genetic and molecular basis of host-pathogen interactions in pigs, and also have wider applications in livestock.

This study assessed the effect of pre-natal social stress and post-natal pain on the reproductive development of young (approximately day 40) pigs. Male pigs carried by sows that were stressed by mixing with unfamiliar older sows for two 1-week periods during mid-pregnancy had lower plasma testosterone (0.54 vs 0.86 ng/ml, S.E.D.=0.11; P=0.014) and oestradiol (E2; 22.9 vs 38.7 pg/ml, S.E.D.=7.80; P=0.021) concentrations compared with males carried by unstressed control sows. Although there was no effect of pre-natal stress on female E2 concentrations, female pigs carried by stressed sows had fewer primordial ovarian follicles (log -4.32/μm² vs -4.00/μm², S.E.D.=0.136; P=0.027). Tail amputation on day 3 after birth reduced E2 concentrations in female (4.78 vs 6.84 pg/ml, S.E.D.=0.86; P=0.03) and in male (25.6 vs 34.9 pg/ml, S.E.D.=3.56; P=0.021) pigs and reduced both testis weight (0.09% of body weight vs 0.10% of body weight, S.E.D.=0.003; P=0.01) and the percentage of proliferating Leydig cells (1.97 vs 2.12, S.E.D.=0.114; P=0.036) compared with sham-amputated littermate controls. There was a significant (P=0.036) interaction between the effects of pre-natal stress and post-natal pain on testicular expression of the steroidogenic enzyme 17α-hydroxylase, such that amputation increased expression in pigs born to control sows, but reduced expression in animals born to stressed sows. This study shows that stressful procedures associated with routine animal husbandry can disrupt the developing reproductive axis. [ABSTRACT FROM AUTHOR]

Individuals show stable differences in their aggressive responses towards unfamiliar conspecifics. We investigated the extent to which variables present during early life could be identified that were correlated with these later individual differences in aggressive behaviour. The behaviour and growth of 125 domestic pigs, Sus scrofa, from 16 litters, were studied from birth until 18 days after weaning, when they were tested on two occasions in resident–intruder tests to measure their aggressiveness. Aggressiveness was affected by litter, although not by sex. A number of early life correlates of later resident–intruder aggressiveness were found at the litter level. Pigs became more aggressive if they had been born into larger litters. Pigs in these aggressive litters were more active in the 8-h period immediately after birth, perhaps taking longer to achieve satiety at the udder. They were also in poorer condition 2 days after birth. Aggressive pigs also engaged in more pushing with littermates over the whole preweaning period. The best correlates of aggressiveness appear to be a number of correlated variables relating to low nutrition, either prenatally or in the early postnatal period. The results are consistent with the concept that early environmental conditions can programme behavioural responses for later life. [Copyright &y& Elsevier]

Piglet-directed aggression by farrowing pigs seriously threatens the welfare of the piglets and also results in economic waste within the pig industry. Pre-weaning piglet mortality in the UK is around 11% with savaging accounting for up to 25% of deaths. The aim of this study was to investigate whether gilts that savage piglets behave differently to non-savaging gilts during the expulsive phase of parturition. The behaviour of the gilts during the 8 h following the birth of the first piglet was recorded. The gilts were categorised as savagers (n=4) or non-savagers (n=15) depending on their response to piglets during farrowing, and then behaviour during farrowing was compared between the two groups. The maternal behaviour during the first 8 h of farrowing differed significantly between the savagers and non-savagers. Savaging gilts were significantly more restless and more responsive towards their piglets during farrowing as characterised by increased posture changing, higher frequency of walking and time spent investigating piglets that approached their head. Overall the results of this study suggest that aberrant maternal behaviour during farrowing involves increased restlessness and responsiveness to piglets, particularly in the early stages of the expulsive phase, which are opposite to the inactivity and passivity suggested to reflect good maternal care in the pig. It is suggested that this restlessness and responsiveness of savaging gilts may not necessarily reflect poor maternal ability, but may be related to the individual’s inability to cope with restrictive environments around farrowing. [Copyright &y& Elsevier]

Summary: In rodents and humans stressful events in early life e.g. maternal deprivation, can increase sensitivity to stress in later life. Humans may become more susceptible to mood disorders, e.g. depression. In livestock species, such as pigs, early weaning is a form of maternal deprivation. We investigated behavioural consequences in 99 female pigs weaned at three different ages (12, 21 and 42 days; d12, d21, d42). Pigs were habituated to an open field arena over 6 days before being given 5-min open-field tests over three subsequent days (days 77–79). Early-weaned pigs (d12) showed behavioural inhibition (reduced vocalisations and lower activity) compared with later-weaned pigs, although in all groups these measures declined over the three tests, so this treatment difference might reflect more rapid habituation to the test in d12 pigs. Long-term effects on mood-related 5-HT receptor subtypes were measured in the brain at 90 days in a random sample of the d12 (n =8) and d42 pigs (n =8), using 3H-ligand-binding and autoradiography and in situ hybridisation histochemistry. There were no differences between weaning ages in binding of 3H-8-OH-DPAT (5-HT1A receptor agonist) or of 3H-ketanserin (5-HT2A receptor antagonist) to any brain region studied. In d12 pigs, 5-HT1A receptor mRNA expression per unit area was 29%, 63%, 52% and 64% lower than in d42 pigs in the parvocellular PVN, amygdala and hippocampal dentate gyrus and pyramidal cell layer, respectively. The ratio of expression per cell to expressing cells per unit area was also lower, by 31%, in the pars horizontalis of the PVN in d12 pigs. Conversely, 5-HT2A receptor mRNA was expressed at a 25% and 28% higher density per unit area in the amygdala and pyramidal cell layer of the hippocampus, respectively, in these d12 pigs. In individual pigs, across brain regions, 5-HT1A receptor mRNA data were 70–79% correlated with binding data but no correlation was found for 5-HT2A data, suggesting different regulatory mechanisms. The behavioural and neurobiological responses to early weaning might represent either dysfunction or adaptation. Further investigation is required. [Copyright &y& Elsevier]

Abstract: Commercial sows are typically confined in crates before and during parturition and remain there throughout lactation. In various animal species including non-lactating pigs, confinement over similar periods leads to adaptive changes in the HPA axis, consistent with chronic stress. To investigate evidence for chronic stress in lactating sows, primiparous sows (gilts) were kept in behaviourally confining crates with straw bedding (CS, n =8) or without bedding (C, n =8) or in larger strawed pens (PS, n =16) between 5 days before parturition until 29 days postpartum (piglets were weaned on day 28). Behavioural and physiological recordings (Plasma ACTH and cortisol) were taken at intervals (baseline), and CRH injections were given on five occasions (days 2, 8, 15, 22 and 29 postpartum). The PS gilts spent more time in substrate-directed behaviour and lying ventrally, and less time lying laterally and sitting than the two crated treatments (C and CS) throughout lactation. Baseline plasma ACTH and cortisol levels showed no treatment differences, although we confirmed that a diurnal pattern exists, with morning (1000 h) cortisol being higher than later in the day. CRH challenge tests suggested changes in the HPA axis, consistent with chronic stress, by the end of the lactation period. Cortisol response to CRH tended to be higher in CS than PS across all days, and by day 29 cortisol response to CRH was significantly higher in CS compared to PS and tended to be higher in C than PS. Cortisol/ACTH ratio following CRH challenge also tended to be higher in the crate treatments (C and CS) by day 29. These data suggest that prolonged confinement in farrowing crates may have a negative impact on sow welfare. [Copyright &y& Elsevier]

Abstract: Post-mixing aggression in commercially housed pigs can be intense and often results in the accumulation of skin lesions. The number of lesions (lesion score, LS) has often been used as a proxy indicator of post-mixing aggression. There has been no previous attempt to quantify the role of different behaviours in the accumulation of lesions. The objective of this work was to investigate the factors that contribute to LS in order to assess the validity of LS as a measure of individual aggressiveness. After mixing into new groups of 12, the durations of reciprocal fighting and bullying, the proportions of fights initiated, won and lost and physical attributes of the pigs were investigated for their impact on LS using multiple regression on a sample of 342 growing pigs. Pig liveweight was the single greatest determinant of LS. The duration spent in reciprocal fighting and being bullied were also significant determinants of the LS and contributed to the total LS in proportions of 0.17 and 0.14, respectively. The proportion of fights initiated, won and lost did not influence the LS for pigs of a given weight. On an individual pig basis, it was impossible to establish the relative importance of reciprocal fighting and the receipt of bullying to the accumulation of lesions by reference to the total LS alone. Engagement in reciprocal fighting was found to result in lesions to the anterior third of the body, whilst the receipt of bullying resulted in lesions accruing on the caudal third of the body. Reference to the location of lesions, in addition to their number, is a refinement of the methodology that potentially allows discrimination of pigs that accumulate lesions as a result of reciprocal fighting or receipt of bulling. A partial replication of the experiment at a second unit (n =84 pigs) with different genotypic, environmental and husbandry conditions confirmed that the duration spent in reciprocal fighting and being bullied were significant determinants of the LS and that the LS approach is applicable across units. Liveweight was not recorded at Unit 2. These results suggest that the LS methodology provides a rapid means of estimating aggressive behavioural phenotypes when reference is made to both the number and location of lesions and pig weight and pen identity effects are accounted for. [Copyright &y& Elsevier]

Abstract: This study provides evidence in the pig that stress experienced during gestation has long-lasting effects on offspring daughters, including their maternal behaviour. Thirty-six primiparous sows were divided into control and two groups that were stressed (by social mixing) during either the second (Mix 2) or third (Mix 3) trimester of pregnancy. We found detrimental effects of mixing on the mothers'' growth, body lesions, and cortisol secretion, but did not observe any significant effects on reproductive parameters including birth weight. At 60 days of age, 48 daughters were randomly selected from the three treatments: half were challenged using a restraint and isolation test. Then, all were culled and brain tissue was collected. In situ hybridisation measurements showed increased expression of CRH mRNA in the PVN in unrestrained Mix 2 and in the amygdala of Mix 2 and Mix 3 daughters. At 67 days, 24 further daughters were mixed to measure their responses to this social stress. All showed increased salivary cortisol secretion, but Mix 2 and Mix 3 daughters showed a greater and longer response than controls. Finally, all 24 were inseminated and at parturition maternal behaviour was measured. Mix 2 and Mix 3 daughters were more restless and more responsive to piglets that approached the head of the sow, traits which previously have been shown to be a component of abnormal maternal behaviour. Indeed, Mix 2 and Mix 3 daughters also tended to bite at their piglets more than control daughters. [Copyright &y& Elsevier]