Third-party intervention and post-conflict behaviour in agonistic encounters of pigs (Sus scrofa).

BACKGROUND: Third-party interference in agonistic contests entails a deliberate intervention in an ongoing fight by a bystanding individual (third party) and may be followed by post-conflict social behaviour to provide support to a specific individual. The mechanisms behind third-party intervention are, however, still largely understudied. The aim of this study was to investigate third-party interference, with the predictions that (1) the interferer derives benefits from its action by winning a fight, (2) that patterns of intervention depend on familiarity, (3) that dyadic fights last longer than triadic fights, and (4) that interferers engage in non-agonistic social behaviours afterwards. Pre-pubertal pigs (Sus scrofa) (n = 384) were grouped with one familiar and four unfamiliar conspecifics (all non-kin) to elicit contests for dominance rank. Third-party interference was analysed for the first 30 min after grouping, along with the behaviour (nosing or aggression), contest duration, contest outcome, and interferer behaviour after the fight (post-conflict social behaviour). RESULTS: Three types of interference were observed: non-agonistic involvement (nose contact) by the interferer in a dyadic fight; a triadic fight with each of three contestants fighting one opponent at a time; and triadic fights with two opponents jointly attacking the third one (two-against-one fights). The likelihood of a third-party intervention to occur did not depend on the presence of a familiar animal in the fight. However, once intervention was triggered, interferers attacked unfamiliar fight initiators more than familiar ones. Two-against-one fights lasted longer than other triadic fights and occurred more often when both initial contestants were females. Results of 110 triadic fights (out of 585 fights in total) revealed that interferers were more likely to win compared to the initial opponents at equal body weight. The most common post-conflict behaviour displayed by the interferer was agonistic behaviour towards another group member, independently of familiarity. CONCLUSIONS: The general lack of discrimination for familiarity suggests interference is not driven by support to familiar individuals in pigs. The results show that intervening in an ongoing fight gives the interferer a high chance of contest success and may be a strategy that is beneficial to the interferer to increase its dominance status.

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.

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.

Cat owners' perception on having a pet cat during the COVID-19 pandemic.

Restrictions during the COVID-19 pandemic may affect the lives of pet animals. We aimed to assess the impact of the COVID-19 pandemic on the welfare of pet cats across countries, as well as the owners' experience in relation to their cat(s). An online survey containing 21 questions was distributed internationally. Questions were related to information about the cat and its behaviour and health, changes in the household due to the pandemic, and how the owner related to the cat. The survey was completed by 324 respondents from 25 different countries. The survey showed that keeping pet cats during the COVID-19 pandemic did not create problems for the owners, except some difficulties in acquiring veterinary care. The majority (67.3%) of respondents reported no changes in their cats' behaviour. When behavioural changes were reported, they were mostly of a positive nature. Owners who took more measures in relation to the cat to prevent the spread of the virus, e.g., reduced contact, were 1.8 times more likely to report changes in the behaviour of their cats but also 3.8 times more likely to report difficulties related to the care of the cat during the pandemic. Two-third of the respondents indicated a reduction of their own psychological tensions due to having a cat during the pandemic. We concluded that the welfare of pet cats, as reported by the owners, was not adversely affected by the pandemic and the human-cat interaction had positive effects on the owners during the lockdown.

The Joint Log-Lift Task: A Social Foraging Paradigm.

Behavioural cooperation is under intense research. Yet, popular experimental paradigms often employ artificial tasks, require training, or do not permit partner choice, possibly limiting their biological relevance. We developed the joint log-lift task, a social foraging paradigm in which animals have to jointly lift a log to each obtain a food reward. The task relies on an obligate strategy, meaning that the only way to benefit is to work jointly. We hypothesised that (1) animals learn to spontaneously solve the task, and that (2) kin and (3) more sociable individuals would engage more often together in the task and achieve greater success than non-kin and less sociable individuals, respectively. We presented the task to 8 groups of juvenile domestic pigs (Sus scrofa domesticus) in their home pen for 30 min daily. Over the course of 9 days, the pigs showed evidence of learning by progressively switching from individual to joint behaviours, leading to 68% (62 out of 91 pigs) spontaneously solving the task. Success was influenced by sociability, but not kinship. There were large differences in success among dyads, hinting at the possible role of social dynamics and inter-individual differences in the ability and/or motivation to solve the task. The joint log-lift task allows researchers to investigate spontaneous cooperative tendencies of individuals, dyads and groups in the home environment through ad libitum engagement with the apparatus. This ecologically relevant paradigm opens the way to investigate social foraging experimentally at large scale, by giving animals free choice about when and with whom to work jointly.

An estimation of the financial consequences of reducing pig aggression.

Animal welfare scientists have accumulated knowledge and developed interventions to improve livestock welfare, but these are poorly adopted in commercial practice. Animal welfare interventions are rarely tested for economic viability and this limits their uptake. This study employs Stochastic Partial Budgeting (SPB) to determine the viability of animal welfare improvements. Aggression between pigs is used as an example because there is a large literature base from which to draw interventions, and the problem has persisted for decades without resolution. Costs and benefits of three interventions to control aggression (pre-weaning socialisation, synthetic maternal pheromones and large social groups) were estimated by reviewing the academic and industry literature and by conducting a survey of sixteen pig farmers. The net effects were compared to farmers' willingness to pay (WTP) for interventions to reduce aggression as identified by recent research. Results are consistent with prior research which indicates that improving animal welfare generally comes at a cost to producers. Nevertheless, pre-weaning socialisation resulted in a neutral or positive net effect 38% of the time and should be central to campaigns promoting the control of aggression in the industry. Exposing pigs to synthetic maternal pheromones did not improve profitability but the net costs were small and within the realms of WTP for a sub-group of farmers with animal welfare goals. The net costs of converting existing buildings in order to house pigs in large social groups were beyond the realms of farmers' WTP. The approach adopted in this study, of combining SPB with WTP from the sector, should be extended to other animal welfare issues.

Impacts of the COVID-19 pandemic on animal behaviour and welfare researchers.

The COVID-19 pandemic has resulted in many changes in the way research is conducted. Some specific groups (e.g. women) and activities (e.g. teaching) may have been disproportionally affected. Our aim was to assess the impact of the COVID-19 pandemic on animal behaviour and welfare researchers' work experience and productivity, focussing on gender, care role, career stage and teaching load. An online survey asked researchers about childcare, research and teaching load and associated changes due to the pandemic, among others, and included the Perceived Stress Scale (PSS) and the Inventory of Socially Supportive Behaviours (ISSB). From June-July 2020, 117 completed responses were received from 28 countries. Time available for writing papers and grants either increased (36 %), decreased (31 %) or these tasks were halted completely (12 %). Perceived productivity was significantly lower for caregivers (P < 0.001) and for men as compared to women (P < 0.001); and low productivity was associated with more stress (higher PSS: P < 0.001). Respondents' experience of the pandemic related to the PSS (b = -0.03 ± 0.02; P = 0.03) and to self-assessed personality traits (P = 0.01). The average PSS of 21 ± 6.5 was greater than the reference value of 15, and was higher when respondents had low job security (P < 0.001) and when they more strongly characterised themselves as perfectionists, hard-working, empathetic and worried (P = 0.02). Respondents who had an intense care role received most social support (P = 0.04). Teaching load increased for 25 % of the respondents but did not significantly relate to any of the response variables. Overall, caregivers and early career researchers faced the most difficulties, and personality traits had a major impact on the ability to cope with the changes caused by the pandemic.

Changes in the health and behaviour of pet dogs during the COVID-19 pandemic as reported by the owners.

The COVID-19 pandemic affects human health, movement and behaviour, and this may consequently influence the behaviour and health of their pets. The aim of this study was to assess the impact of the COVID-19 pandemic on pet dogs' behaviour, as reported by their owners, as well as the owners' experience in relation to their dogs. We hypothesized that dog owners who underwent lockdown or quarantine would indicate more behavioural changes in their dogs and experience support in having a dog during the pandemic. An international online survey asked dog owners questions regarding their household, the dog, and dog-related changes during the pandemic. A total of 688 surveys, collected May-June 2020, were analysed. Respondents were from across Europe (87 %), the Americas (9%), and Asia and Australia (together 4%). Data were analysed in GLMM models with a binary distribution and country included as random variable. The main predictor variable was whether the respondent experienced lockdown (300 respondents, 44 %), quarantine (76 respondents, 11 %) or no restrictions (312 respondents, 45 %). Respondents who underwent lockdown or quarantine were 1.8 times more likely to report behavioural changes in their dogs (p = 0.02), with more negative behavioural changes in the dogs reported by respondents in lockdown than expected by chance. However, overall behavioural changes were more often positive (30 %) than negative (24 %). Respondents in lockdown were 2.6 times more likely to report health changes in their dogs (p = 0.02). The dog was perceived as a source of support during the pandemic: 65 % of the respondents indicated reduced tension due to their dog and 47 % indicated that the ability to walk the dog outside was another benefit. Advantages were reported more by respondents in lockdown and quarantine as compared to respondents who did not face these restrictions (p < 0.001). Difficulties in dog care were increased for respondents who experienced lockdown or quarantine (p < 0.01) and those who had no garden as compared to those who did (p < 0.001). One-third of the respondents took dog-related measures to prevent the spread of the coronavirus, and this was associated with more behavioural changes and more difficulties. In conclusion, lockdown, and to a lesser extent quarantine, may influence the dogs' behaviour and health, or the owners' awareness of it, and can contribute to a perceived tension-reduction in the owners.

Online conferences as an opportunity to enhance inclusiveness in animal behaviour and welfare research: A case study of the ISAE 2020 virtual meeting.

The COVID-19 pandemic caused worldwide disruptions and changes, including in the way research was conducted. One aspect was the cancellation of in-person scientific conferences and the rapid replacement of some into virtual conferences. The aim of this study is to highlight the opportunities that virtual conferences can bring to animal behaviour and welfare research, with a focus on regional diversity and early career researchers (ECRs). The ISAE 2020 virtual meeting was used as a case study. Firstly, conference attendance was compared to the ISAE 2019 in-person international congress. Secondly, a post-conference survey was conducted (n = 142 responses). Data were analysed quantitatively (multinomial models) and qualitatively (word classifications). The organisation by geographical region attracted many non-local attendees and positive feedback was received on the global perspective. The participation from the ISAE developing regions AFRICA (Africa/Central Asia/Middle East), ASIA (South/East/Southeast Asia) and LATAM (Latin America) was higher as compared to the in-person conference (p < 0.001). The most valued advantage for the virtual conference was the reduced cost, followed by the increased ability to participate and the reduced environmental footprint. The most valued advantages did not differ between regions or attendees of different career stages, but an interaction showed that the ability to participate was more appreciated by ECRs in developing regions (p < 0.05). Over 75 % of the respondents ranked the absence of social interaction as the most important disadvantage. Respondents from developed regions were more likely to attend a future virtual conference with a registration fee as compared to those from developing regions (p < 0.05). Respondents most enjoyed the organisation, flexibility, quality of presentations and regional diversity from their virtual experience. This study showed that within applied animal behaviour and welfare science, the virtual format of an international conference can promote participation from diverse regions, especially from less financially privileged groups, but attention should be paid to enhance the social element of a virtual conference.

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.

Intra-Group Lethal Gang Aggression in Domestic Pigs (Sus scrofa domesticus).

Intraspecific coalitional aggression is rare among all species, especially within stable social groups. We report here numerous cases of intraspecific lethal gang aggression within stable groups of domestic pigs. The objective was to describe this extreme aggression and to identify potential causes. Management data were collected from farms with (n = 23) and without (n = 19) gang aggression. From one farm, 91 victims were assessed for skin injuries and body condition score. Lethal gang aggression was significantly associated with deep straw bedding, which may be related to various other factors. Gang aggression tended to occur more in winter, and was unrelated to genetic line, breeding company, group size or feed type. It occurred equally in female-only and mixed sex groups (male-only groups were not represented), from around eight weeks of age. Injuries typically covered the whole body and were more severe on the front of the body. Victims who survived had a lower body condition score and fewer injuries than victims found dead. There are still many unknowns as to why this abnormal social behaviour occurs and it deserves further research attention, both for its applied relevance to animal welfare as for the evolutionary background of lethal gang aggression.

Positive Welfare and the Like: Distinct Views and a Proposed Framework.

Positive welfare and related terms such as good welfare, happiness, and a good life are increasingly used in the animal welfare science literature. Overall, they highlight the welfare benefits of providing animals opportunities for positive experiences, beyond the alleviation of suffering. However, the various terms remain loosely defined and are sometimes used interchangeably, resulting in discrepancy. In this perspective article, we lay out the terms and concepts used in the literature. We identify two distinct views: "hedonic positive welfare," arising from likes and wants and their positive outcomes on welfare; and "positive welfare balance," as an overall positive welfare state based on positive experiences outweighing negative ones. Eudaimonia, satisfaction with one's life, may emerge as a third view. We propose a framework that is applicable across the different views. The "Vienna Framework" outlines different facets: frequency, duration, arousal, context, previous experience, individual differences, sense of agency, and long-term benefit. The framework aims to encourage researchers to consider the relevance of these facets for their own research, to indicate how the facets are affected by different interventions (e.g., greater sense of agency in enriched compared to non-enriched animals), or to compare different topics with respect to the different facets (e.g., high arousal of play behavior and low arousal of social affiliation). We encourage researchers to carefully consider and clearly state how their work falls along these views and facets, conceptually, and operationally. This should prevent dilution of the meaning of positive welfare and thereby preserve its potential to improve the welfare of animals.

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.

Prospects for the Analysis and Reduction of Damaging Behaviour in Group-Housed Livestock, With Application to Pig Breeding.

Innovations in the breeding and management of pigs are needed to improve the performance and welfare of animals raised in social groups, and in particular to minimise biting and damage to group mates. Depending on the context, social interactions between pigs can be frequent or infrequent, aggressive, or non-aggressive. Injuries or emotional distress may follow. The behaviours leading to damage to conspecifics include progeny savaging, tail, ear or vulva biting, and excessive aggression. In combination with changes in husbandry practices designed to improve living conditions, refined methods of genetic selection may be a solution reducing these behaviours. Knowledge gaps relating to lack of data and limits in statistical analyses have been identified. The originality of this paper lies in its proposal of several statistical methods for common use in analysing and predicting unwanted behaviours, and for genetic use in the breeding context. We focus on models of interaction reflecting the identity and behaviour of group mates which can be applied directly to damaging traits, social network analysis to define new and more integrative traits, and capture-recapture analysis to replace missing data by estimating the probability of behaviours. We provide the rationale for each method and suggest they should be combined for a more accurate estimation of the variation underlying damaging behaviours.

Recording behaviour of indoor-housed farm animals automatically using machine vision technology: A systematic review.

Large-scale phenotyping of animal behaviour traits is time consuming and has led to increased demand for technologies that can automate these procedures. Automated tracking of animals has been successful in controlled laboratory settings, but recording from animals in large groups in highly variable farm settings presents challenges. The aim of this review is to provide a systematic overview of the advances that have occurred in automated, high throughput image detection of farm animal behavioural traits with welfare and production implications. Peer-reviewed publications written in English were reviewed systematically following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. After identification, screening, and assessment for eligibility, 108 publications met these specifications and were included for qualitative synthesis. Data collected from the papers included camera specifications, housing conditions, group size, algorithm details, procedures, and results. Most studies utilized standard digital colour video cameras for data collection, with increasing use of 3D cameras in papers published after 2013. Papers including pigs (across production stages) were the most common (n = 63). The most common behaviours recorded included activity level, area occupancy, aggression, gait scores, resource use, and posture. Our review revealed many overlaps in methods applied to analysing behaviour, and most studies started from scratch instead of building upon previous work. Training and validation sample sizes were generally small (mean±s.d. groups = 3.8±5.8) and in data collection and testing took place in relatively controlled environments. To advance our ability to automatically phenotype behaviour, future research should build upon existing knowledge and validate technology under commercial settings and publications should explicitly describe recording conditions in detail to allow studies to be reproduced.

Pig farmers' willingness to pay for management strategies to reduce aggression between pigs.

When deciding whether to invest in an improvement to animal welfare, farmers must trade-off the relative costs and benefits. Despite the existence of effective solutions to many animal welfare issues, farmers' willingness to pay for them is largely unknown. This study modelled pig farmers' decisions to improve animal welfare using a discrete choice experiment focused on alleviating aggression between growing/finishing pigs at regrouping. Eighty-two UK and Irish pig farm owners and managers were asked to choose between hypothetical aggression control strategies described in terms of four attributes; installation cost, on-going cost, impact on skin lesions from aggression and impact on growth rate. If they did not like any of the strategies they could opt to keep their current farm practice. Systematic variations in product attributes allowed farmers' preferences and willingness to pay to be estimated and latent class modelling accounted for heterogeneity in responses. The overall willingness to pay to reduce lesions was low at £0.06 per pig place (installation cost) and £0.01 per pig produced (running cost) for each 1% reduction in lesions. Results revealed three independent classes of farmers. Farmers in Class 1 were unlikely to regroup unfamiliar growing/finishing pigs, and thus were unwilling to adopt measures to reduce aggression at regrouping. Farmers in Classes 2 and 3 were willing to adopt measures providing certain pre-conditions were met. Farmers in Class 2 were motivated mainly by business goals, whilst farmers in Class 3 were motivated by both business and animal welfare goals, and were willing to pay the most to reduce aggression; £0.11 per pig place and £0.03 per pig produced for each 1% reduction in lesions. Farmers should not be considered a homogeneous group regarding the adoption of animal welfare innovations. Instead, campaigns should be targeted at subgroups according to their independent preferences and willingness to pay.