Piglets' behaviour and performance in relation to sow characteristics.

The importance of maternal care in commercial pig production is largely ignored. The sow has little possibility to interact with her piglets, and piglets are often subjected to early weaning or artificial rearing. This study aimed to investigate aspects of physiological and behavioural maternal provisioning that contribute to offspring outcomes. We hypothesised that better maternal care and nutritional provisioning would relate positively to piglet immunity, growth and behaviour. Nineteen sows and their litters were studied in free-farrowing pens. Oxytocin and tumour necrosis factor-α in colostrum/milk and salivary cortisol were sampled from sows throughout lactation. Sows were assessed for dominance rank, response to handling, maternal defensiveness, suckling initiation and termination, posture and sow-piglet contact. Piglets were weighed, measured for body mass index (BMI) and sampled for blood (Immunoglobulin G; at birth). After weaning, they experienced a human approach test (HAT) and novel object test. Correlations were explored between individual sow characteristics, individual piglet outcomes, and between sow characteristics and piglet outcomes averaged by litter. Significant correlations between sow and piglet factors were analysed at the litter level in mixed models with piglet outcomes as response variables and sow characteristics as predictor variables, while accounting for sow parity, litter size and batch. Litters grew faster when their sow had lower cortisol values (P = 0.03), while sows with lower cortisol levels had more successful suckling bouts and engaged in greater amounts of sow-piglet contact. Litters had a lower BMI at weaning when the sow had a higher milk fat percentage at d3. Litters of the most dominant sows took longer to approach the human in the HAT, while litters of sows with higher cortisol at d0 took longer to approach the novel object when assessed on correlations (r = 0.82, P < 0.001) but not when the model accounted for parity and litter size (P = 0.35). Only some of the measured nutritive and non-nutritive sow factors influenced litter performance and behaviour, with parity and litter size also playing a role. Given the continued increase in litter size, but also the interest in loose-housed lactation pens for sows, further research on sows' maternal investment and how it can be optimised is warranted.

Characterizing candidate decompression rates for hypobaric hypoxic stunning of pigs. Part 1: Reflexive behavior and physiological responses.

Alternatives to carbon dioxide (CO2) stunning for the commercial slaughter of pigs are urgently needed because there is robust evidence that exposing pigs to hypercapnic environments is associated with pain, fear, and distress. Hypobaric hypoxia (via gradual decompression, also known as Low Atmospheric Pressure Stunning or LAPS) has been validated in poultry as a humane option, but its potential to improve the welfare of pigs at slaughter is unknown. We investigated the potential of hypobaric hypoxia to reliably elicit a non-recovery state in anesthetized weaner-grower pigs within a commercially viable timeframe. We determined the effect of candidate decompression rates (40, 60, 80, 100 ms-1, at two cycle durations 480 s and 720 s) on a range of physiological and reflexive behavioral indicators of hypoxia and death. We found that the decompression rates tested caused a 100% death rate. As expected, the decompression rate had overarching effects on behavioral and physiological markers of hypoxia and death, with faster decompression rates resulting in shorter latencies to cardiac arrest and cessation of breathing. We observed a higher proportion of pigs displaying repeated and prolonged whole-body movements (likely indicative of convulsive activity) at higher frequencies when we applied the slowest decompression rate (40 ms-1) compared to all other rates. Since these responses may impact the carcass and meat quality, the slower rate of decompression (40 ms-1) should be excluded as a candidate decompression rate. Furthermore, given the marginal effects of decompression rate on physiological indicators of death and reflexive behavioral parameters, we also recommend that the fastest rate tested (100 ms-1) is excluded in further study on conscious pigs (to prevent conscious animals from being exposed to unnecessary faster decompression rates which may compromise animal welfare). This work represents a necessary proof of principle step and confirms the potential of gradual decompression for stunning purposes in pigs. Importantly, however, the data presented provide no information on the welfare outcomes associated with decompression in conscious pigs. Subsequent work should focus on the comprehensive welfare assessment of intermediate decompression rates to determine the potential of hypobaric hypoxia to provide a humane stunning method for pigs.

Characterizing candidate decompression rates for hypobaric hypoxic stunning of pigs. Part 2: Pathological consequences.

Pigs are commonly stunned pre-slaughter by exposure to carbon dioxide (CO2), but this approach is associated with significant welfare concerns. Hypobaric hypoxia, achieved with gradual decompression (also known as Low Atmospheric Pressure Stunning or LAPS) may be an alternative, allowing the retention of welfare friendly handling approaches and group stunning. Although validated in poultry, the feasibility and welfare consequences of gradual decompression for pigs are unknown. Here, we characterize pathological changes in 60 pigs resulting from exposure to a range of candidate decompression curves (ranging from 40 to 100 ms-1 ascent equivalent, with two cycle durations 480 and 720 s). To protect welfare, we worked on unconscious, terminally anesthetized pigs which were subject to detailed post-mortem examinations by a specialized porcine veterinary pathologist. All pigs were killed as a result of exposure to decompression, irrespective of cycle rate or length. Pigs showed no external injuries during ante-mortem inspections. Exposing pigs to decompression and the unavoidable subsequent recompression resulted in generalized congestion of the carcass, organs and body cavities including the ears, oral cavity, conjunctivae and sclera, mucosa of other external orifices (anus and vulva), nasal planum, nasal cavities including nasal conchae, frontal sinuses, cranium, meninges, brain, larynx, trachea, lungs, heart, parietal pleura of the thoracic cavity, peritoneum of the abdominal cavity, stomach, small intestine, caecum, colon, liver, spleen and kidneys and representative joint cavities in the limbs (stifles and elbows). Various severities of hemorrhage were observed in the conjunctivae and sclera, mucosa of other external orifices (anus and vulva), nasal cavities including nasal conchae, frontal sinuses, cranium, meninges, brain, larynx, tracheal lumen, lungs, parietal pleura of the thoracic cavity, liver, spleen and kidneys and representative joint cavities in the limbs (stifles and elbows). In general, faster decompression rates produced higher scores, but in the conjunctivae, sclera and kidneys, faster decompression rates were associated with marginally lower congestion scores. There was considerable individual variation in pathological scores across all body regions. The congestion and hemorrhage observed could translate into welfare harms in conscious pigs undergoing this type of stunning, depending when in the cycle the damage is occurring, but no welfare related conclusions can be drawn from the responses of unconscious pigs. Since recompression is always required, its effects cannot be separated from decompression, however cessation of cardiac activity several minutes before recompression should have eliminated any haemodynamic effects relating to cardiac function and blood pressure. This study represents the first systematic attempt to identify candidate rate profiles to underpin future explorations of decompression as a stunning method for pigs. These pathological findings also inform discussions about the likely carcass quality implications of this novel stunning method.

Sexual dimorphism in ritualized agonistic behaviour, fighting ability and contest costs of Sus scrofa.

BACKGROUND: Sexual selection has driven sexual dimorphism in agonistic behaviour in many species. Agonistic behaviour is fundamentally altered by domestication and captivity, but it is unclear whether ancestral sex differences remain. We aimed to evaluate the effect of sex on agonistic behaviour, fighting ability and contest costs. We studied this in domestic pigs (Sus scrofa) where aggression compromises welfare, and sexual dimorphism in aggression has been inconclusively demonstrated. Behaviour and physiology of 827 male and female juvenile pigs were studied during resident-intruder tests and dyadic contests at various ages, while accounting for the relative body weight difference between the opponents. RESULTS: Males won in 79% of contests against females, even when at a large weight disadvantage. The effect of sex increased with age, with males having a 138 times higher likelihood of winning than females when 13 weeks old. In dyadic contests, males invested more time in non-damaging agonistic display behaviour and took longer before escalating into damaging aggression. Males showed ritualized display that included foaming from the mouth and piloerection of the neck hair, which was nearly always absent in females. Contest costs in terms of contest duration, blood lactate and skin lesions where higher for males, especially when fighting another male. CONCLUSIONS: Profound sex differences were present for agonistic behaviour, fighting ability and contest costs, and became more pronounced as animals got older. Males invested more in ritualized display before escalating into costly fights, whereas females attacked sooner but also terminated contests more rapidly and with fewer costs. The sexual dimorphism in agonistic behaviour in juvenile domestic pigs is in line with the evolutionary relevance for females' maternal defence and males' competition for females.

Once bitten, twice shy: Aggressive and defeated pigs begin agonistic encounters with more negative emotions.

Aggression between unfamiliar commercial pigs is common and likely invokes strong emotions in contestants. Furthermore, contest outcomes affect subsequent aggressive behaviour, suggesting a potential lasting influence on affective state. Here we used a combination of qualitative and quantitative methods to assess the emotional expression of pigs in agonistic encounters. We investigated how recent victory or defeat influences emotions expressed in a subsequent contest, and the role of aggressiveness as a personality trait in emotional expression. We observed the pre-escalation contest behaviour (second contest; age 13 wks) in animals of different aggressiveness (categorised using two resident intruder tests as Agg+ or Agg-, age 9 wks), which had recently won or lost a contest (first contest; 10 wks). We measured gaze direction and ear position. Observers watched video clips of the initial 30 s of the second contest and evaluated the emotional expression of 57 pigs (25 contest 1 winners, 32 contest 1 losers) using qualitative behavioural assessment (QBA) with a fixed list of 20 descriptive terms. QBA identified three principal components (PCs), accounting for 68% of the variation: PC1 (agitated/tense to relaxed/content), PC2 (fearful/aimless to confident/enjoying) and PC3 (listless/ indifferent). Agg- pigs and males showed a more positive emotionality (PC2). PC1 and PC3 were unaffected by first contest outcome and aggressiveness. Agg+ pigs were more likely to hold their ears back (X2 =7.8, p = 0.005) during the early contest period. Differences in attention were detected in the contest outcome × aggressiveness interaction (χ24.3, p = 0.04), whereby approaching the opponent was influenced by winning and losing in the Agg- pigs only. QBA and gaze behaviour reveal differences in emotional valence between pigs of different aggressiveness: less aggressive pigs may be more susceptible to the emotional impact of victory and defeat but overall, more aggressive pigs express more negative emotionality at the start of agonistic encounters.

DIAGNOSING AND CATEGORIZING LEPROSY IN LIVE EURASIAN RED SQUIRRELS (SCIURUS VULGARIS) FOR MANAGEMENT, SURVEILLANCE, AND TRANSLOCATION PURPOSES.

The presence of Mycobacterium lepromatosis and Mycobacterium leprae in Eurasian red squirrel (Sciurus vulgaris, ERS) carcasses throughout the British Isles, and leprosy as a disease, have recently been reported using histological and molecular diagnostic methods. In 2016, the first longitudinal study of ERS affected by leprosy was initiated. One of the main challenges was the reliable diagnosis of leprosy in live ERS, which is important for (a) welfare and case management and (b) surveillance or pretranslocation screening efforts. We explored diagnostic methods ranging from detailed clinical assessment and informative categorization of observed lesions, thermal imaging, serology (antiphenolic glycolipid-I antibody [αPGL-I] detection) to molecular methods (polymerase chain reaction [PCR]). For PCR the ear was established as the optimal sampling site. Based on the experiences from this 2-yr study we propose an objective categorization system for clinical lesions and a diagnostic framework for the combination of the diagnostic tools we found to be effective in live ERS: clinical assessment, αPGL-I serology, and PCR. Thermal imaging did not offer additional information for leprosy diagnostics in ERS. We propose an amended definition of leprosy lesions in ERS as "skin areas of local hair loss, in which a firm-rubbery, glossy swelling develops, that may ulcerate" and standardized terminology for describing ERS leprosy status. The information presented forms the basis of a consistent, reliable diagnostic and reporting system for leprosy cases in ERS.

Play fighting social networks do not predict injuries from later aggression.

Early play fighting mimics later aggression in many species, and may, therefore, be expected to reduce costs from later aggressive interactions. Using social network analysis (SNA) the effect of a central play fighting network position on later skin lesions from aggression was assessed in domestic pigs. Piglets (n = 263) were kept in litter groups or socialised pre-weaning with another litter to enhance play fighting experience. Play fighting was recorded for 1.5 h per day over 6 days pre-weaning. Play fighting network centrality was quantified using measures of individual network position and entire network structure (degree, eigenvector, betweenness, clustering coefficient). Skin lesions from aggression were counted after a dyadic contest and at 24 h and 3 weeks following group mixing. Pigs with play fighting interactions with many partners experienced fewer lesions from the dyadic contest (in-degree, p = 0.01) and tended to received fewer lesions 3 weeks after group mixing (degree, p = 0.088) but no other play fighting centrality measures affected the number of lesions at any point. The benefits of play fighting were therefore limited to specific aggressive social contexts. The tendency of socialised piglets to play fight with non-littermates did not affect subsequent lesions. We advocate the use of SNA over approaches that only consider dyadic interactions to further our understanding of the influence of early social group interactions on later life experience.

Winner-loser effects overrule aggressiveness during the early stages of contests between pigs.

Contest behaviour, and in particular the propensity to attack an unfamiliar conspecific, is influenced by an individual's aggressiveness, as well as by experience of winning and losing (so called 'winner-loser effects'). Individuals vary in aggressiveness and susceptibility to winner-loser effects but the relationship between these drivers of contest behaviour has been poorly investigated. Here we hypothesise that the winner-loser effect on initiation of agonistic behaviour (display, non-damaging aggression, biting and mutual fighting) is influenced by aggressiveness. Pigs (n = 255) were assayed for aggressiveness (tendency to attack in resident-intruder tests) and then experienced two dyadic contests (age 10 and 13 weeks). Agonistic behaviour, up to reciprocal fighting, in contest 2 was compared between individuals of different aggressiveness in the RI test and experiences of victory or defeat in contest 1. Winner-loser effects were more influential than aggressiveness in determining initiation of agonistic behaviour. After accruing more skin lesions in contest 1, individuals were less likely to engage in escalated aggression in contest 2. The interaction between aggressiveness and winner-loser experience did not influence contest behaviour. The results suggest that aggressiveness does not compromise learning from recent contest experience and that reducing aggressiveness is unlikely to affect how animals experience winning and losing.

The Association Between Play Fighting and Information Gathering during Subsequent Contests.

Many hypotheses regarding the evolution of social play have been suggested, including the development of later-life assessment skills. However, the link between play fighting experience and information gathering during contests has yet to be examined. This paper explores the association between play fighting and contest assessment strategy in the domestic pig (Sus scrofa). Using an established framework, we provide evidence suggesting play fighting frequency may affect the extent to which individuals incorporate information regarding their own and their competitors' resource holding potential (RHP) in escalation decisions. Pigs were allocated as 'high play' or 'low play' based upon their relative play fighting frequency. To maximise variation in play, 12 litters underwent a socialisation treatment while the remaining 12 litters were kept isolated within their home pen (i.e. control treatment). At eight weeks of age contests were staged between pairs of unfamiliar pigs, using 19 'high play' dyads and 19 'low play' dyads. While 'high play' dyads were observed to rely on a pure self-assessment strategy, 'low play dyads' did not meet the predictions of either self- or mutual assessment, suggesting their contest behaviour may have been motivated by alternative factors. We suggest that early life play fighting may therefore allow individuals to develop an accurate estimate of their RHP.

Infrared thermography of agonistic behaviour in pigs.

Infrared thermography (IRT) or thermal imaging is increasingly being used as a non-invasive method to gain information on animals' physiological and emotional state. IRT has the potential to serve as a non-invasive quantitative assessment method but few studies have examined its utility in predicting welfare-relevant outcomes of dynamic scenarios relevant to commercial farming. This study used 1284 thermal images taken from 46 pigs in a controlled test environment while they engaged in an agonistic encounter (dyadic contest) at 13 wk. of age. Images were taken of the complete body from a dorsal perspective. A pilot study indicated that a rectangular thermal window on the back region was the most suitable and reliable area for obtaining temperature data in this situation. From this thermal window, the average, minimum and maximum temperature, standard deviation and coefficient of variation (CV) were obtained. These were analysed in relation to contest phase (from non-contact assessment, through escalated fighting to retreat), fight occurrence, contest duration, contest outcome (winner/loser status) and changes in blood glucose, blood lactate, and skin injuries. Variables showed a strong change in response to the moment of contest resolution (retreat of the loser); temperatures reduced sharply and CV increased, but did not differ between winners and losers. Contests that included a fight showed lower temperatures. Contest duration, body weight and sex only had minor influences on the temperatures. As the drop in temperature at contest resolution was irrespective of contest intensity, and the pattern was similar in winners and losers, this data potentially reflects vasoconstriction as a result of psychological stress rather than solely a physiological change. The study shows that peripheral temperature, as recorded by IRT, responds to the intensity and phases of a contest and may allow new insight into the physiological and welfare outcomes of aggressive behaviour.

Advantages of social skills for contest resolution.

Animal contests are natural interactions that occur to obtain or defend resources such as food and territory. Selection should favour individuals that can win contests with minimal costs in terms of energy expenditure or injuries. We hypothesized that social skills contribute to animals' assessment abilities in a contest situation and thereby will shorten contest duration. Animals were either raised in early life conditions stimulating the development of social skills, termed socialization or not (control). Contests between 342 pigs at eight weeks old (171 dyads) were studied for opponent assessment ability (using a game theoretical approach), examining duration and escalation, social behaviours performed, injuries and outcome. Contesting dyads were from the same treatment group and varied in body weight, a validated measure of resource holding potential (RHP). Socialized animals had shorter contests that were resolved with fewer injuries and they showed more ritualized display behaviour, consistent with mutual assessment. Furthermore, there was evidence of a novel form of opponent assessment in the socialized group revealed by a positive relationship between winner RHP and fight duration. In conclusion, social skills enabled more rapid establishment of dominance relationships at lower cost. Besides its evolutionary relevance, these findings may also contribute towards improving animal welfare.

Socialisation and its effect on play behaviour and aggression in the domestic pig (Sus scrofa).

There is considerable interest in how early life experiences shape behavioural development. For example, the socialisation of unfamiliar pigs pre-weaning has been suggested to decrease aggression during later life. However, the behavioural mechanisms behind this socialisation effect remain unexplored. We allowed 12 litters of domestic pigs (Sus scrofa) to move freely between their home pen and a neighbouring pen (socialisation) during the lactation period, while keeping 12 litters isolated in their home pen (control). Contrary to predictions, socialisation did not result in higher levels of social play. However, control individuals engaged in more sow directed play than those that underwent socialisation. Consistent with predictions, males performed more piglet directed play than females. Social play behaviour pre-weaning was found to be highly concordant within individuals from both treatments. Post-weaning, 148 pigs were selected to perform two resident-intruder tests to assay aggressiveness. As predicted, socialised individuals were quicker to attack than controls, although females were more aggressive than males. Additionally, play fighting experience was found to negatively correlate with attack latency in females, supporting the hypothesis that early-life play experience is likely to be sexually dimorphic when males and females show pronounced differences in their later-life social behaviour.

Evaluation of reticuloruminal pH measurements from individual cattle: Sampling strategies for the assessment of herd status.

The application of pH observations to clinical practice in dairy cattle is based on criteria derived primarily from single time-point observations more than 20 years ago. The aims of this study were to evaluate these criteria using data collected using continuous recording methods; to make recommendations that might improve their interpretation; and to determine the relationship between the number of devices deployed in a herd and the accuracy of the resulting estimate of the herd-mean reticuloruminal pH. The study made use of 815,475 observations of reticuloruminal pH values obtained from 75 cattle in three herds (one beef and two twice-daily milking herds) to assess sampling strategies for the diagnosis of sub-acute rumen acidosis (SARA), and to evaluate the ability of different numbers of bolus devices to accurately estimate the true herd-mean reticuloruminal pH value at any time. The traditional criteria for SARA provide low diagnostic utility, the probability of detection of animals with pH values below specified thresholds being affected by a strong effect of time of day and herd. The analysis suggests that regardless of time of feeding, sampling should be carried out in the late afternoon or evening to obtain a reasonable probability of detection of animals with pH values below the threshold level. The among-cow variation varied strongly between herds, but for a typical herd, if using reticuloruminal pH boluses to detect a predisposition to fermentation disorders while feeding a diet that is high in rapidly fermentable carbohydrates, it is recommended to use a minimum of nine boluses.

Facial expression as a potential measure of both intent and emotion.

Facial expressions convey information on emotion, physical sensations, and intent. The much debated theories that facial expressions can be emotions or signals of intent have largely remained separated in animal studies. Here we integrate these approaches with the aim to 1) investigate whether pigs may use facial expressions as a signal of intent and; 2) quantify differences in facial metrics between different contexts of potentially negative emotional state. Facial metrics of 38 pigs were recorded prior to aggression, during aggression and during retreat from being attacked in a dyadic contest. Ear angle, snout ratio (length/height) and eye ratio from 572 images were measured. Prior to the occurrence of aggression, eventual initiators of the first bite had a smaller snout ratio and eventual winners showed a non-significant tendency to have their ears forward more than eventual losers. During aggression, pigs' ears were more forward orientated and their snout ratio was smaller. During retreat, pigs' ears were backwards and their eyes open less. The results suggest that facial expressions can communicate aggressive intent related to fight success, and that facial metrics can convey information about emotional responses to contexts involving aggression and fear.

Long Term Benefits on Social Behaviour after Early Life Socialization of Piglets.

Early life socialization of piglets has been shown to reduce piglet aggression at weaning, but information on sow health and long-term benefits is lacking. We aimed to assess how socialization impacts sow udder quality and long-term pig behaviour and growth. At two weeks of age, 65 litters either experienced socialization with one other litter (SOC) or did not (control; CON). Sows (housed in farrowing crates) were scored for teat damage and piglets were observed for aggressive behaviour (resident-intruder test) and growth and skin lesions up to 11 weeks under conventional farm conditions (including weaning and regrouping). At weaning, SOC sows had more teat damage than CON sows (p = 0.04). SOC piglets had double the number of lesions 24 h post-socialization compared to the control (19 versus 8; p < 0.001). In the resident-intruder test, more SOC pigs attacked the intruder (SOC 78%; CON 66%; p < 0.01), and attacked more quickly (p = 0.01). During regrouping (week 8), SOC pigs had 19% fewer lesions (SOC 68; CON 84; p < 0.05), but three weeks later, groups did not differ. Growth was unaffected by treatment. Overall, socialized piglets seem to be equipped with greater confidence or agonistic skills, leading to fewer injuries from fighting up to at least six weeks after socialization.

Lateralization influences contest behaviour in domestic pigs.

Cerebral lateralization, i.e. hemispheric asymmetries in structure and function, relates in many species to a preference to attack from their left. Lateralization increases cognitive capacity, enabling the simultaneous processing of multiple sources of information. Therefore, lateralization may constitute a component of fighting ability (Resource Holding Potential), and/or influence the efficiency of information-gathering during a contest. We hypothesized that lateralization will affect contest outcome and duration, with an advantage for more strongly lateralized individuals. In 52 dyadic contests between weight-matched pigs (Sus scrofa; n = 104; 10 wk age), the direction of orientation towards the opponent was scan sampled every 10 s. Laterality indexes (LI) were calculated for the direction and strength of lateralization. Up to 12.5% of the individuals showed significant lateralization towards either the right or left but lateralization was absent at the population level. In line with our hypothesis, animals showing strong lateralization (irrespective of direction) had a shorter contest duration than animals showing weak lateralization. Winners did not differ from losers in their strength or direction of lateralization. Overall the results suggest that cerebral lateralization may aid in conflict resolution, but does not directly contribute to fighting ability, and will be of value in the study of animal contests.

The influence of experience on contest assessment strategies.

Animal contest behaviour has been widely studied, yet major knowledge gaps remain concerning the information-gathering and decision-making processes used during encounters. The mutual assessment strategy, where the individual assesses its own fighting ability (Resource Holding Potential, RHP) and compares it to that of its opponent, is least understood. We hypothesise that individuals need experience of agonistic encounters to become proficient at mutual assessment. Pigs (Sus scrofa, n = 316) were contested twice. In between contests, animals did or did not (control) receive intense fighting experience. A substantial proportion of the contests reached an outcome with a clear winner without fighting. Non-escalation was highest in RHP asymmetric dyads of the second contest, irrespective of experience. In contest 1 (no experience) and in contest 2 for the experienced animals, costs increased with loser RHP and where unaffected by winner RHP, suggesting a self-assessment strategy. In contest 2 control dyads, which only had experience of one prior contest, a negative relation between winner RHP and costs suggested mutual assessment during the pre-escalation phase but not during escalated aggression. This reveals that a brief and relatively mild experience can be beneficial in the development of mutual assessment whereas profound experience may result in adoption of a self-assessment strategy.