Genetics of animal temperament: aggressive behaviour at mixing is genetically associated with the response to handling in pigs

Selection for social genetic effects in purebred pigs improves behaviour and handling of their crossbred progeny

BACKGROUND

In commercial pig production, reduction of harmful social behavioural traits, such as ear manipulation and tail biting, is of major interest. Moreover, farmers prefer animals that are easy to handle. The aim of this experiment was to determine whether selection on social breeding values (SBV) for growth rate in purebred pigs affects behaviour in a weighing crate, lesions from ear manipulation, and tail biting of their crossbred progeny. Data were collected on crossbred F1 pigs allocated to 274 pens, which were progeny of purebred Landrace sows and Yorkshire boars from a DanBred nucleus herd.

RESULTS

Behaviour in the weighing crate scored on a three-level scale showed that groups of pigs with high SBV for growth rate were significantly calmer than groups of pigs with low SBV (P < 0.027). When the mean SBV in the group increased by 1 unit, the proportion of pigs that obtained a calmer score level was increased by 14%. A significant (p = 0.04), favourable effect of SBV was found on both the number of pigs with ear lesions in the group and the mean number of ear lesions per pig. For a 1 unit increase in mean SBV, the mean number of lesions per pig decreased by 0.06 from a mean of 0.98. Individual severity of ear lesions conditional upon the number of ear lesions was also significantly affected (p = 0.05) by the mean SBV in the group. In groups for which the mean SBV increased by 1 unit, the proportion of pigs that were observed with a lower severity score was increased by 20% on a three-level scale. Most pigs received no tail biting injuries and no effect of SBV was observed on the tail injury score.

CONCLUSIONS

After 7 weeks in the finisher unit, crossbred progeny with high SBV were calmer in the weighing crate and had fewer ear lesions. These results indicate that selection of purebred parents for SBV for growth rate will increase welfare in their crossbred progeny by decreasing the number of ear lesions and making them easier to handle.

Estimating genetics of body dimensions and activity levels in pigs using automated pose estimation

Pig breeding is changing rapidly due to technological progress and socio-ecological factors. New precision livestock farming technologies such as computer vision systems are crucial for automated phenotyping on a large scale for novel traits, as pigs’ robustness and behavior are gaining importance in breeding goals. However, individual identification, data processing and the availability of adequate (open source) software currently pose the main hurdles. The overall goal of this study was to expand pig weighing with automated measurements of body dimensions and activity levels using an automated video-analytic system: DeepLabCut. Furthermore, these data were coupled with pedigree information to estimate genetic parameters for breeding programs. We analyzed 7428 recordings over the fattening period of 1556 finishing pigs (Piétrain sire x crossbred dam) with two-week intervals between recordings on the same pig. We were able to accurately estimate relevant body parts with an average tracking error of 3.3 cm. Body metrics extracted from video images were highly heritable (61–74%) and significantly genetically correlated with average daily gain (r_g = 0.81–0.92). Activity traits were low to moderately heritable (22–35%) and showed low genetic correlations with production traits and physical abnormalities. We demonstrated a simple and cost-efficient method to extract body dimension parameters and activity traits. These traits were estimated to be heritable, and hence, can be selected on. These findings are valuable for (pig) breeding organizations, as they offer a method to automatically phenotype new production and behavioral traits on an individual level.

Behavioural reactivity testing in sheep indicates the presence of multiple temperament traits

Temperament in sheep is commonly presented as unidimensional, with a 'nervous' temperament indicative of fear and reactivity towards humans and novel environments. However, temperament is multidimensional, with some traits expressed only under certain conditions (context-specific). There is evidence that a common temperament test in sheep, the isolation-box (IB), measures level of activity and not fearfulness as intended, and that behaviours measured in the IB test are indicative of different traits. To investigate this, 16 behavioural responses to a human, to being startled, and to confinement (IB test) were measured in 89 lambs, twice, three months apart. Our results agree with previous studies that vocalisations in all tests and locomotion in two, show high repeatability over time. A principal component analysis identified that vocalisations are domain-general, and are indicative of the trait 'sociability', however locomotion is context-specific' and captures the traits 'exploration-avoidance', 'boldness-shyness' and 'general activity'. A cluster analysis identified four behavioural profiles that indicate the trait 'boldness-shyness' captures reactivity towards humans. This suggests the IB test, which measures 'general activity', is unsuitable for measuring reactivity towards humans in sheep, and that when studying the impact of temperament on other factors, multiple conditions should be used when identify temperament traits.

Systematic review of animal-based indicators to measure thermal, social, and immune-related stress in pigs

The intense nature of pig production has increased the animals’ exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals’ coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.

Responsiveness of domesticated goats towards various stressors following long-term cognitive test exposure

Current evidence suggests that frequent exposure to situations in which captive animals can solve cognitive tasks may have positive effects on stress responsiveness and thus on welfare. However, confounding factors often hamper the interpretation of study results. In this study, we used human-presented object-choice tests (in form of visual discrimination and reversal learning tests and a cognitive test battery), to assess the effect of long-term cognitive stimulation (44 sessions over 4-5 months) on behavioural and cardiac responses of female domestic goats in subsequent stress tests. To disentangle whether cognitive stimulation per se or the reward associated with the human-animal interaction required for testing was affecting the stress responsiveness, we conditioned three treatment groups: goats that were isolated for participation in human-presented cognitive tests and rewarded with food ('Cognitive', COG treatment), goats that were isolated as for the test exposure and rewarded with food by the experimenter without being administered the object-choice tests ('Positive', POS treatment), and goats that were isolated in the same test room but neither received a reward nor were administered the tests ('Isolation', ISO treatment). All treatment groups were subsequently tested in four stress tests: a novel arena test, a novel object test, a novel human test, and a weighing test in which goats had to enter and exit a scale cage. All treatment groups weretested at the same two research sites, each using two selection lines, namely dwarf goats, not selected for production traits, and dairy goats, selected for high productivity. Analysing the data with principal component analysis and linear mixed-effects models, we did not find evidence that cognitive testing per se (COG-POS contrast) reduces stress responsiveness of goats in subsequent stress tests. However, for dwarf goats but not for dairy goats, we found support for an effect of reward-associated human-animal interactions (POS-ISO contrast) at least for some stress test measures. Our results highlight the need to consider ontogenetic and genetic variation when assessing stress responsiveness and when interacting with goats.

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.

A Systematic Review of Genomic Regions and Candidate Genes Underlying Behavioral Traits in Farmed Mammals and Their Link with Human Disorders

Simple Summary

This study is a comprehensive review of genomic regions associated with animal behavior in farmed mammals (beef and dairy cattle, pigs, and sheep) which contributes to a better understanding of the biological mechanisms influencing the target indicator trait and to gene expression studies by suggesting genes likely controlling the trait, and it will be useful in optimizing genomic predictions of breeding values incorporating biological information. Behavioral mechanisms are complex traits, genetically controlled by multiple genes spread across the whole genome. The majority of the genes identified in cattle, pigs, and sheep in association with a plethora of behavioral measurements (e.g., temperament, terrain use, milking speed, tail biting, and sucking reflex) are likely controlling stimuli reception (e.g., olfactory), internal recognition of stimuli (e.g., neuroactive ligand–receptor interaction), and body response to a stimulus (e.g., blood pressure, fatty acidy metabolism, hormone signaling, and inflammatory pathways). Six genes were commonly identified between cattle and pigs. About half of the genes for behavior identified in farmed mammals were also identified in humans for behavioral, mental, and neuronal disorders. Our findings indicate that the majority of the genes identified are likely controlling animal behavioral outcomes because their biological functions as well as potentially differing allele frequencies between two breed groups (subjectively) clustered based on their temperament characteristics.

Abstract

The main objectives of this study were to perform a systematic review of genomic regions associated with various behavioral traits in the main farmed mammals and identify key candidate genes and potential causal mutations by contrasting the frequency of polymorphisms in cattle breeds with divergent behavioral traits (based on a subjective clustering approach). A total of 687 (cattle), 1391 (pigs), and 148 (sheep) genomic regions associated with 37 (cattle), 55 (pigs), and 22 (sheep) behavioral traits were identified in the literature. In total, 383, 317, and 15 genes overlap with genomic regions identified for cattle, pigs, and sheep, respectively. Six common genes (e.g., NR3C2, PITPNM3, RERG, SPNS3, U6, and ZFAT) were found for cattle and pigs. A combined gene-set of 634 human genes was produced through identified homologous genes. A total of 313 out of 634 genes have previously been associated with behavioral, mental, and neurologic disorders (e.g., anxiety and schizophrenia) in humans. Additionally, a total of 491 candidate genes had at least one statistically significant polymorphism (p-value < 0.05). Out of those, 110 genes were defined as having polymorphic regions differing in greater than 50% of exon regions. Therefore, conserved genomic regions controlling behavior were found across farmed mammal species and humans.

Rearing in female-only groups and dietary mineral supplementation improves sow welfare in the early parities and lifetime performance

The lifetime performance of commercial sows relies on longevity, which is dependent on good health and reproductive performance. However, there is a high rate of wastage of sows in the early parities, which is influenced by the way they are managed and housed during rearing. This study investigated the carry-over effect of gilt rearing strategy on the measures of welfare and performance. Eighty sows were reared using a two by two factorial design: rearing group composition [GC; female-only (FEM) or mixed-sex (MIX) from weaning] with or without supplementary minerals (CON = control diet; SUPP = control + Cu, Zn, and Mn) from 5 wk into the finisher stage. Once served, gilts were managed in a dynamic group gestation pen and fed a standard gestating sow diet. Locomotory ability was scored (0 to 5) and salivary cortisol measured five times during the first gestation, and human approach tests were carried out on day 108. Hooves were scored for injuries and legs for bursas at day 70 of the first gestation, at first weaning, and at the second farrowing. Sow behavior in the hoof scoring crate (movement, vocalization, and handling ease) was also recorded. The number of piglets born alive and dead during the first five parities was recorded as was the performance of the first litter to finish. Data were analyzed using general or generalized linear mixed models, as appropriate, using SAS (v 9.4). There was no effect (P > 0.05) of rearing treatment on locomotory ability, bursa score, the total number of piglets born, or on offspring growth. However, there was an interaction between GC and supplementary minerals (P < 0.05) on salivary cortisol levels with MIX × SUPP sows having the highest levels. Total hoof scores and heel erosion scores were higher in sows reared in MIX groups (P < 0.01), and CON sows tended to have higher horizontal crack scores (P = 0.06). Sows from MIX kicked more at weaning than FEM (P < 0.05) and tended to be more fearful in the forced human approach test (P = 0.1) where they are scored on their reaction to being approached. They also had more stillborn piglets across all five parities than FEM (P < 0.05). Overall, rearing replacement sows in FEM groups and dietary mineral supplementation had minimal but beneficial effects on their subsequent welfare and performance.

Identification of Single Nucleotide Polymorphisms in Porcine MAOA Gene Associated with Aggressive Behavior of Weaned Pigs after Group Mixing

Simple Summary

Monoamine Oxidase A (MAOA) gene had been reported as a candidate gene of aggressive behavior in several species. In the present study, the most aggressive and docile weaned pigs in each pen after group mixing were selected to identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region of porcine MAOA was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in the MAOA gene were genotyped, of which six SNPs had significant differences in allele frequency between the aggressive and docile pigs. Four linked SNPs in porcine MAOA gene were associated with aggressive behavior in weaned pigs after mixing, which can be used as candidate molecular markers for aggressive behavior in pigs.

Abstract

Understanding the genetic background underlying the expression of behavioral traits has the potential to fasten the genetic progress for reduced aggressive behavior of pigs. The monoamine oxidase A (MAOA) gene is known as the “warrior” gene, as it has been previously linked to aggressive behavior in humans and livestock animals. To identify single nucleotide polymorphisms in porcine MAOA gene associated with aggressive behavior of pigs, a total of 500 weaned pigs were selected and mixed in 51 pens. In each pen, two aggressive and two docile pigs (a total of 204 pigs) were selected based on their composite aggressive score (CAS). Ear tissue was sampled to extract genomic DNA. Constructs containing variable lengths of truncated porcine MAOA promoter were used to determine the promoter activity by a dual luciferase reporter system. The core promoter region was located at −679 bp to −400 bp. A total of nine single nucleotide polymorphisms (SNPs) in MAOA gene were genotyped, of which six SNPs had significant differences (p < 0.05) in allele frequency between the aggressive and docile pigs. Linkage disequilibrium and association analyses showed that the pigs inherited the wild genotypes showed more aggressive behavior (p < 0.05) than pigs with the mutant genotypes of the four linked SNPs, rs321936011, rs331624976, rs346245147, and rs346324437. In addition, pigs of GCAA haplotype were more (p < 0.05) aggressive than the pigs with GCGA or ATGG haplotype. The construct containing the wild genotype GG of rs321936011 had lower (p = 0.031) promoter activity compared to the mutant genotype AA. These results suggest that the four linked SNPs in MAOA gene could be considered as a molecular marker for behavioral trait selection in pigs.

Suitability of traits related to aggression and handleability for integration into pig breeding programmes: Genetic parameters and comparison between Gaussian and binary trait specifications

Changes in husbandry systems as well as consumers' increasing demands for animal welfare lead to increasing importance of traits such as handleability and aggressiveness in pigs. However, before using such novel traits for selection decisions, information on genetic parameters for these traits for the specific population is required. Therefore, weight gain and behaviour-related traits were recorded in 1004 pigs (814 Pietrain x German Landrace crossbred, 190 German Landrace purebred) at different ages. Behaviour indicators and tests were assessed and conducted, respectively under commercial farm conditions and included scoring of skin lesions (twice) and behaviour during backtests (twice), injections (once), handling (twice) and weighing (three times). Since behaviour scores often exhibit suboptimal statistical properties for parametric analyses, variance components were estimated using an animal model assuming a normal (Gaussian, GA; all traits) and additionally a binary distribution of variables (BI; using a logit-link function for all behaviour traits). Heritabilities for behavioural traits ranged from 0.02 ± 0.04 (finishing pig handling test; BI) to 0.36 ± 0.08 (backtest 2; GA) suggesting that some of the traits are potentially useful for genetic selection (e.g. finishing pig weighing test: h2 (GA) = 0.20 ± 0.07). Only minor differences were observed for results from binary and Gaussian analyses of the same traits suggesting that either approach might yield valid results. However, four-fold cross-validation using correlations between breeding values of a sub-set of animals for the sample trait finishing pig weighing score indicated slight superiority of the logit model (r = 0.85 ± 0.04 vs. r = 0.77 ± 0.03). Generally, only weak to moderate associations were found between behavioural reactions to the same test at different ages (rp ≤ 0.11 for weighing at different ages; rp = 0.30 but rg (GA) = 0.84 ± 0.11 for the backtests) as well as between reactions to different tests. Therefore, for inclusion of behaviour traits into breeding programmes, and considering high labour input required for some tests such as the backtest, it is recommended to assess behaviour during situations that are relevant and identical to practical conditions, while the use of indicator traits generally does not appear to be a very promising alternative.

Genome-wide association analyses of lesion counts in group-housed pigs

Aggression in group-housed pigs is a welfare concern and can negatively affect production. Skin lesions are reliable indicators of aggression and are moderately heritable, suggesting that selective breeding may reduce aggression. To further understand the genetic control of behavioral traits, such as the aggressive response to regrouping, associated single nucleotide polymorphisms (SNPs) can be identified within the genome, and the region in which these SNPs are located can be related to known genes. To investigate SNPs associated with aggression, 1093 purebred Yorkshire pigs were strategically remixed into new groups of familiar and unfamiliar animals at three life stages and lesion counts were recorded. Genomic best linear unbiased prediction (GBLUP) models were fitted for each trait. The genetic additive effect was obtained from a genetic relationship matrix constructed from the 50 924 SNPs. SNP effects and their variances were estimated from the GBLUP objects. SNPs that were associated with a significant portion of the trait variance were identified for lesions to the anterior (three SNPs, FDR <5%) and central (one SNP, FDR <5%) portions of the body in grow-finish pigs. These SNPs were located on chromosome 11, suggesting that chromosome 11 contains a region explaining variation in lesion counts that should be further explored to identify genes underlying biological control of aggression.

Personality Research in Mammalian Farm Animals: Concepts, Measures, and Relationship to Welfare

Measuring and understanding personality in animals is a rising scientific field. Much research has been conducted to assess distinctive individual differences in behavior in a large number of species in the past few decades, and increasing numbers of studies include farm animals. Nevertheless, the terminology and definitions used in this broad scientific field are often confusing because different concepts and methods are used to explain often synonymously applied terms, such as personality, temperament and coping style. In the present review we give a comprehensive overview of the concepts and terms currently used in animal personality research and critically reveal how they are defined and what they measure. First, we shortly introduce concepts describing human personality and how these concepts are used to explain animal personality. Second, we present which concepts, methods and measures are applied in farm animal personality research and show that the terminology used seems to be somehow species-related. Finally, we discuss some findings on the possible impact of personality on the welfare of farm animals. The assessment of personality in farm animals is of growing scientific and practical interest. Differences in theoretical frameworks and methodological approaches may also entail the diverse use of the different concepts between basic and applied research approaches. We conclude that more consistency is needed in using different theoretical concepts, terms and measures, especially in farm animal personality research. The terms coping style and temperament, which are used in different ways, should not be examined as independent concepts, but rather should be considered as different aspects of the whole personality concept. Farm animal personality should be increasingly considered for the improvement of animal housing, management, breeding and welfare.

Behavioural genetic differences between Chinese and European pigs

Aggression is a heritable trait and genetically related to neurotransmitter-related genes. Behavioural characteristics of some pig breeds are different. To compare the genetic differences between breeds, backtest and aggressive behaviour assessments, and genotyped using Sequenom iPLEX platform were performed in 50 Chinese indigenous Mi pigs and 100 landrace-large white (LLW) cross pigs with 32 SNPs localized in 11 neurotransmitter-related genes. The genetic polymorphisms of 26 SNPs had notable differences (P < 0.05) between Mi and LLW. The most frequent haplotypes were different in DBH, HTR2A, GAD1, HTR2B,MAOA and MAOB genes between Mi and LLW. The mean of backtest scores was significantly lower (P < 0.001) for Mi than LLW pigs. Skin lesion scores were greater (P < 0.01) in LLW pigs than Mi pigs. In this study, we have confirmed that Chinese Mi pigs are less active and less aggressive than European LLW pigs, and the genetic polymorphisms of neurotransmitter-related genes, which have been proved previously associated with aggressive behaviour, have considerable differences between Mi and LLW pigs.

Estimation of genetic parameters for lesion scores and growth traits in group-housed pigs

Pigs housed in groups are remixed with unfamiliar individuals, which can trigger aggressive interactions, potentially compromising animal welfare. Skin lesions are a reliable indicator trait of aggression and are moderately heritable, suggesting that aggression may be reduced through selection. This study estimated genetic parameters of skin lesions of pigs at multiple life stages, explored genetic correlations of skin lesions between age groups and body location, and studied the relationship between skin lesions and production traits of commercial importance. A population of 1,079 Yorkshire pigs was strategically remixed into new groups of familiar and unfamiliar animals at 3 life stages (weaning, grow-finish, and mature gilts). Skin lesions (fresh, bright red cuts) were counted immediately prior to mixing and 24 h and 3 wk after mixing across 3 body regions: anterior, central, and caudal. Weights were recorded prior to each mixing event. Prior to slaughter, backfat thickness and loin muscle area were determined using ultrasound. Univariate analyses were performed to obtain heritability estimates of lesion scores. Bivariate analyses were performed with response variables being skin lesions, weight gain per life stage, backfat thickness, or loin muscle area, depending on the relationship of interest, to obtain correlations. Lesion score heritabilities ranged from 0.10 to 0.40 and were significant ( < 0.05). Heritability was highest for lesions on the anterior region of the body for 24 h and 3 wk after mixing. Lesions to the central and caudal areas showed the highest genetic correlation at each stage of production, whereas those to the anterior and caudal regions had the lowest correlation. The highest genetic correlation was found between the mature gilt and grow-finish stages, whereas the weaning and mature gilt stages had the lowest correlations. Genetic correlations between lesions and production traits were not significantly different from 0 for weight gain and backfat thickness, but loin muscle area was negatively correlated with lesions ( = 1.17 × 10, = 2.30 × 10, and = 6.08 × 10 for anterior, central, and caudal lesions, respectively). These results are promising for the industry because they suggest that pigs selected for reduced lesions will show increased loin muscle area without negative effects on growth. Alternatively, selection for these production traits would not increase lesions.

Heritability of the backtest response in piglets and its genetic correlations with production traits

The backtest response of a pig gives an indication of its coping style, that is, its preferred strategy to cope with stressful situations, which may in turn be related to production traits. The objective of this study was therefore to estimate the heritability of the backtest response and estimate genetic correlations with production traits (birth weight, growth, fat depth and loin depth). The backtest was performed by placing the piglet on its back for 60 s and the number of struggles (NrS) and vocalizations (NrV), and the latency to struggle and vocalize (LV) was recorded. In total, 992 piglets were subjected to the backtest. Heritability estimates for backtest traits were statistically moderate (although high for behavioral traits), with LV having the highest heritability estimate (0.56±0.10, P<0.001) and NrS having the lowest estimate (0.37±0.09, P<0.001). Backtest traits also had high genetic correlations with each other, with vocalization traits (NrV and LV) having the highest (-0.94±0.03, P<0.001), and NrS with NrV the lowest correlation (0.70±0.09, P<0.001). No significant correlations were found between backtest traits and production traits, but correlations between NrS and birth weight (-0.38±0.25), and NrV and loin depth (-0.28±0.19) approached significance (P=0.07). More research into genotype-by-environment interactions may be needed to assess possible connections between backtest traits and production traits, as this may depend on the circumstances (environment, experiences, etc.). In conclusion, heritability estimates of backtest traits are high and it would therefore be possible to select for them. The high genetic correlations between backtest traits indicate that it may be possible to only consider one or two traits for characterization and selection purposes. There were no significant genetic correlations found between backtest traits and production traits, although some of the correlations approached significance and hence warrant further research.

ANIMAL BEHAVIOR AND WELL-BEING SYMPOSIUM: Interaction between coping style/personality, stress, and welfare: Relevance for domestic farm animals

This paper will argue that understanding animal welfare and the individual vulnerability to stress-related disease requires a fundamental understanding of functional individual variation as it occurs in nature as well as the underlying neurobiology and neuroendocrinology. Ecological studies in feral populations of mice, fish, and birds start to recognize the functional significance of phenotypes that individually differ in their behavioral and neuroendocrine response to environmental challenge. Recent studies indicate that the individual variation within a species may buffer the species for strong fluctuations in the natural habitat. Similarly, evolutionary ancient behavioral trait characteristics have now been identified in a range of domestic farm animals including cattle, pigs, and horses. Individual variation in behavior can be summarized in a 3-dimensional model with coping style, emotionality, and sociality as independent dimensions. These dimensions can be considered trait characteristics that are stable over time and across situations within the individual. This conceptual model has several consequences. First, the coping style dimension is strongly associated with differential stress vulnerability. Social stress studies show that proactive individuals are resilient under stable environmental conditions but vulnerable when outcome expectancies are violated. Reactive individuals are, in fact, rather flexible and seem to adapt more easily to a changing environment. A second consequence relates to genetics and breeding. Genetic selection for one trait usually implies selection for other traits as well. It is discussed that a more balanced breeding program that takes into account biologically functional temperamental traits will lead to more robust domestic farm animals. Finally, the relationship between temperamental traits, animal production, fitness, and welfare is discussed.

The short-term behavioural response of sows, but not gilts, to a social stimulus is related to sow aggressiveness in groups

This study examined relationships between the behavioural response of pregnant gilts (n=200, gestation 1) and sows (n=200, gestation 2) to a live, similarly-aged female pig (unfamiliar pig test, UPT) and to a fibre-glass model pig (model pig test, MPT), and aggressive behaviour on the day after mixing (day 2). Sows with a short latency to make contact with an unfamiliar sow in the UPT were more likely to deliver high levels of aggression at day 2 of gestation 2 (P=0.005), but this relationship was stronger when a model pig was used (P<0.001). Similarly, sows with a long duration of tactile contact with the model pig in the MPT were more likely to deliver high levels of aggression at day 2 of gestation 2 (P=0.015), but this relationship was weaker than that between aggression and the latency to contact the model pig. When the terms the latency to contact the unfamiliar pig in the UPT and the model pig in the MPT, as well as the duration of contact with the model pig in the MPT, were included in an overall model of aggression at day 2 of gestation 2, behaviour towards the unfamiliar pig became not statistically significant (P>0.05). A strong relationship was not apparent with gilts (P>0.05). Thus, the socially inexperienced pig may not be an ideal model for sow behaviour. This study indicates that sows with a short latency to contact a model pig are more likely to be aggressive when mixed into groups.

Puppy Temperament Assessments Predict Breed and American Kennel Club Group but Not Adult Temperament

Puppy assessments for companion dogs have shown mixed long-term reliability. Temperament is cited among the reasons for surrendering dogs to shelters. A puppy temperament test that reliably predicts adult behavior is one potential way to lower the number of dogs given to shelters. This study used a longitudinal design to assess temperament in puppies from 8 different breeds at 7 weeks old (n = 52) and 6 years old (n = 34) using modified temperament tests, physiological measures, and a follow-up questionnaire. For 7-week-old puppies, results revealed (a) puppy breed was predictable using 3 variables, (b) 4 American Kennel Club breed groups had some validity based on temperament, (c) temperament was variable within litters of puppies, and (d) certain measures of temperament were related to physiological measures (heart rate). Finally, puppy temperament assessments were reliable in predicting the scores of 2 of the 8 adult dog temperament measures. However, overall, the puppy temperament scores were unreliable in predicting adult temperament.

Genetic associations between maternal traits and aggressive behaviour in Large White sows

The present study examined the possibilities and consequences of selecting pigs for reduced aggression and desirable maternal behaviour. Data were recorded from 798 purebred Large White gilts, with an age of 217±17.7 (mean±SD) days, which were observed at mixing with unfamiliar conspecifics. The reaction of the sows towards separation from their litter was assessed for 2022 litters from 848 Large White sows. Sows' performance during their time in the farrowing unit was scored based on the traits farrowing behaviour (i.e. need of birth assistance), rearing performance (i.e. litter quality at day 10 postpartum (pp)), usability (i.e. additional labour input during lactation period e.g. for treatments) and udder quality of the sow (i.e. udder attachment). For agonistic behaviour, traits heritabilities of h 2=0.11±0.04 to h 2=0.28±0.06 were estimated. For the sow's reaction towards separation from her litter low heritabilities were found (h 2=0.03±0.03 for separation test on day 1 pp and h 2=0.02±0.03 for separation test on day 10 pp). Heritabilities for lactating sow's performance (farrowing behaviour, rearing performance, usability of the sow and udder quality) in the farrowing unit ranged from h 2=0.03±0.02 to h 2=0.19±0.03. Due to these results it can be assumed that selection for these traits, for example, for udder quality or reduced aggression, is possible. Antagonistic associations were found between separation test on day 1 pp and different measures of aggressiveness (r g =-0.22±0.26 aggressive attack and r g =-0.41±0.33 reciprocal fighting). Future studies should determine economic as well as welfare-related values of these traits in order to decide whether selection for these traits will be reasonable.

Effects of group housing on sow welfare: a review

Factors that have been shown to impact the welfare of group-housed sows are discussed in this review. Floor space allowance markedly affects sow welfare. In addition to quantity of floor space, the quality of space is important: spatial separation between sows can be provided with visual or physical barriers and stalls. Whereas 1.4 m/sow is insufficient, further research is required to examine space effects in the range of 1.8 to 2.4 m/sow in more detail. The period immediately after mixing has the most pronounced effects on aggression and stress, and therefore, well-designed mixing pens offer the opportunity to reduce aggression, injury, and stress while allowing the social hierarchy to quickly form. Because hunger is likely to lead to competition for feed or access to feeding areas, strategies to reduce hunger between meals through higher feeding levels, dietary fiber, or foraging substrate should be examined. However, feeding systems, such as full-body feeding stalls, can also affect aggression and stress by providing protection at feeding, but deriving conclusions on this topic is difficult because research directly comparing floor feeding, feeding stalls, and electronic sow feeder systems has not been conducted. Familiar sows engage in less aggression, so mixing sows that have been housed together in the previous gestation may reduce aggression. Although there is evidence in other species that early experience may affect social skills later in life, there are few studies on the effects of early "socialization" on aggressive behavior of adult sows. Genetic selection has the potential to reduce aggression, and therefore, continued research on the opportunity to genetically select against aggressiveness and its broader implications is required. Most research to date has examined mixing sows after insemination and knowledge on grouping after weaning is limited.

The effect of selection for residual feed intake on scale-activity and scale-exit scores in Yorkshire gilts

The objectives of the present study were to use scale-activity and scale-exit scores to (1) determine the extent to which selection for improved residual feed intake (RFI) correlates with individual gilt temperament, (2) determine whether the timing of assessment affects the scores, and (3) determine whether gilts habituate to the process of weighing. To achieve these objectives, 192 grow–finish purebred Yorkshire gilts (39.7 ± 5.7 kg; 98 ± 6 days old) were utilised. Ninety-six gilts were from the 5th generation of a line selected for low residual feed intake (LRFI), and 96 gilts were from the 5th generation of a randomly selected control line (CRFI). Gilt activity and exit behaviour were scored on the weigh scale. The activity score was taken at two time points, namely, t = 0 (immediately on the back gate closing on the weight scale) and t = 15 (15 s later). Activity was assessed using a 5-point scoring system (1 = calm, minimal movement; 5 = continuous rapid movement and an escape attempt), and exit score was assessed using a 3-point scoring system (1 = no encouragement needed, full exit; 3 = encouragement needed). Gilts were weighed once every 2 weeks (each weighing considered a testing round) for a maximum of eight scores per gilt. Statistical differences were identified in all rounds for activity between genetic lines, except Rounds 2, 4 and 5. For both lines, gilt-activity scores decreased over rounds. The LRFI line began with a lower activity score (2.31 vs 2.65 ± 0.13), but did not experience as great of a drop in average score over rounds as did the CRFI gilts (0.62 vs 1.21). By the end of the trial, the CRFI gilts scored lower than the LRFI gilts. Activity was greater at t = 15 than at t = 0. Although timing affected the score, the pattern was similar, and so consistency will be more important than timing procedure. For exit scores, in Rounds 5 and 7, the LRFI line scored lower than the CRFI line, and there was a trend for the LRFI line to score lower in Round 6. Across all gilts, the mean exit score increased slowly throughout the trial. In conclusion, selection for lower RFI in purebred Yorkshires has an effect on activity score but this relationship is complex and warrants further research. The observation that gilts become habituated to the process of weighing supports the conclusion that the process is not aversive.

Scientific assessment of animal welfare

Animal welfare is a state within the animal and a scientific perspective provides methodologies for evidence-based assessment of an animal's welfare. A simplistic definition of animal welfare might be how the animal feels now. Affective experiences including emotions, are subjective states so cannot be measured directly in animals, but there are informative indirect physiological and behavioural indices that can be cautiously used to interpret such experiences. This review enunciates several key science-based frameworks for understanding animal welfare. The biological functioning and affective state frameworks were initially seen as competing, but a recent more unified approach is that biological functioning is taken to include affective experiences and affective experiences are recognised as products of biological functioning, and knowledge of the dynamic interactions between the two is considered to be fundamental to managing and improving animal welfare. The value of these two frameworks in understanding the welfare of group-housed sows is reviewed. The majority of studies of the welfare of group-housed sows have employed the biological functioning framework to infer compromised sow welfare, on the basis that suboptimal biological functioning accompanies negative affective states such as sow hunger, pain, fear, helplessness, frustration and anger. Group housing facilitates social living, but group housing of gestating sows raises different welfare considerations to stall housing, such as high levels of aggression, injuries and stress, at least for several days after mixing, as well as subordinate sows being underfed due to competition at feeding. This paper highlights the challenges and potential opportunities for the continued improvement in sow management through well-focused research and multidisciplinary assessment of animal welfare. In future the management of sentient animals will require the promotion of positive affective experiences in animals and this is likely to be a major focus for animal welfare science activity in the early twenty-first century.

Animal welfare and society concerns finding the missing link

Young adults in developed countries are distanced from agriculture and the meat industry needs to do a better job of communicating with them. A major welfare concern is slaughter without stunning. Other concerns, such as poor stunning or high levels of bruising, can be easily corrected by management who is committed to maintaining high standards. Another concern is biological system overload, occurring when animals are bred for more productivity. Researchers and industry need to determine optimum production levels instead of maximums. Retailers are major drivers of animal welfare standards enforcement and they respond to pressure from both activists and consumers.

Variance components of aggressive behavior in genetically highly connected Pietrain populations kept under two different housing conditions

Mixing of unfamiliar pigs is a standard management procedure in commercial pig production and is often associated with a period of intense and physically damaging aggression. Aggression is considered a problem for animal welfare and production. The objective of the present paper was to investigate the genetic background of aggressive behavior traits at mixing of unfamiliar gilts under 2 different housing conditions. Therefore, a total of 543 purebred Pietrain gilts, from 2 nucleus farms (farm A: n = 302; farm B: n = 241) of 1 breeding company, were tested at an average age of 214 d (SD 12.2 d) for aggressive behavior by 1 observer. Observations included the frequencies of aggressive attack and reciprocal fighting during mixing with unfamiliar gilts. On farm A 41% of the gilts were purebred Pietrains, whereas 59% were purebred Landrace or Duroc gilts. On the farm B 42% of the gilts were purebred Pietrains, and 58% purebred Large White gilts. The average size of the newly mixed groups of gilts was 28 animals on farm A and 18 animals on farm B. The Pietrain gilts from the 2 herds were genetically closely linked. They were the offspring of 96 sires, with 64% of these sires having tested progeny in both farms. There were clear differences in the housing of the animals between the 2 farms. The test pen on farm A had a solid concrete floor littered with wooden shavings and was equipped with a dry feeder. On farm B there was a partly slatted floor, and the gilts were fed by an electronic sow feeder. Mean space allowance was 2.6 m(2)/gilt on farm A and 3.9 m(2)/gilt on farm B. Although large interindividual differences existed, gilts from farm B performed numerically more aggressive attack (mean 1.12, SD 1.42 vs. mean 0.71, SD 1.20) and reciprocal fighting (mean 0.78, SD 0.98 vs. mean 0.44, SD 0.82) when compared with gilts from farm A. The heritabilities and additive genetic variances for behavioral traits were estimated with a linear animal model and were on a low level in farm A (h(2) = 0.11, SE = 0.07, and σ(2)a = 0.12 for aggressive attack and h(2) = 0.04, SE = 0.07, and σ(2)a = 0.02 for reciprocal fighting) and on a moderate level in farm B (h(2) = 0.29, SE = 0.13, and σ(2)a = 0.44 for aggressive attack and h(2) = 0.33, SE = 0.12, and σ(2)a = 0.27 for reciprocal fighting). For both aggressive attack and reciprocal fighting, genetic correlation of the same trait between farm A and farm B was 1.0. Therefore, aggressive behavior does not seem to be influenced by genotype × environment interactions. Under these circumstances aggressions in group housing can be reduced by genetic selection against aggressive behavior. Therewith, the welfare and health of sows will ultimately increase.

Indirect genetic effects and housing conditions in relation to aggressive behaviour in pigs

Indirect Genetic Effects (IGEs), also known as associative effects, are the heritable effects that an individual has on the phenotype of its social partners. Selection for IGEs has been proposed as a method to reduce harmful behaviours, in particular aggression, in livestock and aquaculture. The mechanisms behind IGEs, however, have rarely been studied. The objective was therefore to assess aggression in pigs which were divergently selected for IGEs on growth (IGEg). In a one generation selection experiment, we studied 480 offspring of pigs (Sus scrofa) that were selected for relatively high or low IGEg and housed in homogeneous IGEg groups in either barren or enriched environments. Skin lesion scores, a proxy measure of aggression, and aggressive behaviours were recorded. The two distinct IGEg groups did not differ in number of skin lesions, or in amount of reciprocal fighting, both under stable social conditions and in confrontation with unfamiliar pigs in a 24 h regrouping test. Pigs selected for a positive effect on the growth of their group members, however, performed less non-reciprocal biting and showed considerably less aggression at reunion with familiar group members after they had been separated during a 24 h regrouping test. The enriched environment was associated with more skin lesions but less non-reciprocal biting under stable social conditions. Changes in aggression between pigs selected for IGEg were not influenced by G×E interactions with regard to the level of environmental enrichment. It is likely that selection on IGEg targets a behavioural strategy, rather than a single behavioural trait such as aggressiveness.

Genetic associations between behavioral traits and direct-social effects of growth rate in pigs

This study examined the behavioral consequences of selecting pigs using a social genetic model for growth. Calculations enable each member of a group of pigs to be given a direct breeding value (DBV) and a social breeding value (SBV), which can be summarized into a total breeding value (TBV) for growth. Selection for growth TBV could affect animal behavior because social effects account for within-group interactions. Data were recorded from 96 groups of Yorkshire and Yorkshire × Landrace pigs in a nucleus herd. Each group contained 15 pigs fed ad libitum from 2 feeders; the space allowance was 0.85 m2/pig. Average daily gain was quantified from 35 to 100 kg of BW. Fighting and bullying activity at mixing (period 1), lying frequency 3 wk after mixing (period 2), and counts of skin lesions in periods 1 and 2 were recorded. The DBV for these traits were estimated with a classic animal model. We simulated different correlations between the direct genetic effect and the social genetic effect on growth rate (r(DS)), 2 components that respectively determine a pig's genetic capacity to grow and its genetic influence on growth of group mates: r(DS) was successively assumed to be 0 and ±0.12, ±0.20, ±0.29, and ±0.58. Finally, the correlations between DBV, SBV, and TBV for ADG, as well as the DBV for behavior and skin lesions, were calculated and tested for a level of significance at P < 0.05. The gradient from negative to positive values of r(DS) refers to a progressive path running from genetic antagonism to genetic mutualism for growth. If rDS in the population truly ranged between -0.58 and -0.20, correlations for TBV for ADG with DBV for fighting and bullying progressively increased with rDS. Consequently, if rDS was low (between -0.12 and +0.12) or positive (>+0.12), pigs with high TBV for ADG had higher DBV for bullying other pigs in the group and for fighting than pigs with lower TBV for ADG. Pigs with high TBV for ADG did not differ from other pigs in their DBV for lesions to the anterior part of the body, but they had a lower DBV for posterior lesions, whereas in period 2, they had higher DBV for posterior lesions and lower DBV for lying. Under genetic mutualism for growth and in housing conditions similar to those in the present study, selection for growth TBV would promote the rapid establishment of the dominance relationships, with more aggressive contests among group mates at mixing. Pigs would subsequently be more active but, judging by skin lesions, less willing to fight in a more stable social situation.

Identification of chromosomal locations associated with tail biting and being a victim of tail-biting behaviour in the domestic pig (Sus scrofa domesticus)

The objective of this study was to identify loci associated with tail biting or being a victim of tail biting in Norwegian crossbred pigs using a genome-wide association study with PLINK case-control analysis. DNA was extracted from hair or blood samples collected from 98 trios of crossbred pigs located across Norway. Each trio came from the same pen and consisted of one pig observed to initiate tail biting, one pig which was the victim of tail biting and a control pig which was not involved in either behaviour. DNA was genotyped using the Illumina PorcineSNP60 BeadChip whole-genome single-nucleotide polymorphism (SNP) assay. After quality assurance filtering, 53,952 SNPs remained comprising 74 animals (37 pairs) for the tail biter versus control comparison and 53,419 SNPs remained comprising 80 animals (40 pairs) for the victim of tail biting versus control comparison. An association with being a tail biter was observed on Sus scrofa chromosome 16 (SSC16; p = 1.6 × 10(-5)) and an unassigned chromosome (p = 3.9 × 10(-5)). An association with being the victim of tail biting was observed on Sus scrofa chromosomes 1 (SSC1; p = 4.7 × 10(-5)), 9 (SSC9; p = 3.9 × 10(-5)), 18 (SSC18; p = 7 × 10(-5) for 9,602,511 bp, p = 3.4 × 10(-5) for 9,653,881 bp and p = 5.3 × 10(-5) for 29,577,783 bp) and an unassigned chromosome (p = 6.1 × 10(-5)). An r(2) = 0.96 and a D' = 1 between the two SNPs at 9 Mb on SSC18 indicated extremely high linkage disequilibrium, suggesting that these two markers represent a single locus. These results provide evidence of a moderate genetic association between the propensity to participate in tail-biting behaviour and the likelihood of becoming a victim of this behaviour.

Diversifying and correlational selection on behavior toward conspecific and heterospecific competitors in brook stickleback (Culaea inconstans)

Behaviors toward heterospecifics and conspecifics may be correlated because of shared mechanisms of expression in both social contexts (nonadaptive covariation) or because correlational selection favors adaptive covariation. We evaluated these hypotheses by comparing behavior toward conspecifics and heterospecifics in brook stickleback (Culaea inconstans) from three populations sympatric with and three allopatric from a competitor, the ninespine stickleback (Pungitius pungitius). Behavioral traits were classified into three multivariate components: overt aggression, sociability, and activity. The correlation of behavior between social contexts for both overt aggression and activity varied among populations in a way unrelated to sympatry with ninespine stickleback, while mean aggression was reduced in sympatry. Correlations in allopatric populations suggest that overt aggression and activity may genetically covary between social contexts for nonadaptive reasons. Sociability was rarely correlated in allopatry but was consistently correlated in sympatry despite reduced mean sociability, suggesting that correlational selection may favor a sociability syndrome in brook stickleback when they coexist with ninespine stickleback. Thus, interspecific competition may impose diversifying selection on behavior among populations, although the causes of correlated behavior toward conspecifics and heterospecifics and whether it can evolve in one social context independent of the other may depend on the type of behavior.

Repeatability and heritability of behavioural types in a social cichlid

Aim. The quantitative genetics underlying correlated behavioural traits (''animal personality") have hitherto been studied mainly in domesticated animals. Here we report the repeatability (R) and heritability (h(2)) of behavioural types in the highly social cichlid fish Neolamprologus pulcher. Methods. We tested 1779 individuals repeatedly and calculated the h(2) of behavioural types by variance components estimation (GLMM REML), using 1327 offspring from 162 broods from 74 pairs. Results. Repeatability of behavioural types was significant and considerable (0.546), but declined from 0.83 between tests conducted on the same day, to 0.19 on tests conducted up to 1201 days apart. All h(2) estimates were significant but low (e.g., pair identity h(2) = 0.15 ± 0.03 SE). Additionally, we found significant variation between broods nested within the parent(s), but these were not related to several environmental factors tested. Conclusions. We conclude that despite a considerable R, h(2) in this cichlid species is low, and variability in behavioural type appears to be strongly affected by other (non)genetic effects.

Breeding for behavioural change in farm animals: practical, economic and ethical considerations

In farm animal breeding, behavioural traits are rarely included in selection programmes despite their potential to improve animal production and welfare. Breeding goals have been broadened beyond production traits in most farm animal species to include health and functional traits, and opportunities exist to increase the inclusion of behaviour in breeding indices. On a technical level, breeding for behaviour presents a number of particular challenges compared to physical traits. It is much more difficult and time-consuming to directly measure behaviour in a consistent and reliable manner in order to evaluate the large numbers of animals necessary for a breeding programme. For this reason, the development and validation of proxy measures of key behavioural traits is often required. Despite these difficulties, behavioural traits have been introduced by certain breeders. For example, ease of handling is now included in some beef cattle breeding programmes. While breeding for behaviour is potentially beneficial, ethical concerns have been raised. Since animals are adapted to the environment rather than the other way around, there may be a loss of ‘naturalness’ and/or animal integrity. Some examples, such as breeding for good maternal behaviour, could enhance welfare, production and naturalness, although dilemmas emerge where improved welfare could result from breeding away from natural behaviour. Selection against certain behaviours may carry a risk of creating animals which are generally unreactive (‘zombies’), although such broad effects could be measured and controlled. Finally, breeding against behavioural measures of welfare could inadvertently result in resilient animals (‘stoics’) that do not show behavioural signs of low welfare yet may still be suffering. To prevent this, other measures of the underlying problem should be used, although cases where this is not possible remain troubling.

Selection against aggressiveness in pigs at re-grouping: practical application and implications for long-term behavioural patterns

The routine mixing of pigs causes aggression that cannot be greatly reduced by low-cost environmental changes. The variability and heritability of aggressiveness are discussed and both appear adequate to make selection against aggressiveness worthwhile in grower-stage pigs. Selection would require rapid phenotyping of many animals for which a validated indicator genetically correlated to aggressive behaviour is required. Three potential indicators are discussed (attack latency, number of skin lesions and relationship to non-social behavioural traits). Attack latency correlates with post-mixing aggressiveness under research conditions but attacks are delayed under commercial conditions reducing the practicability of the trait for selection. Correlations between aggressiveness and responses to non-social challenges, such as the back-test, are not always consistent. Lastly, the counting of skin lesions is rapid, and the number of lesions has a moderate heritability and is genetically correlated with involvement in aggressive behaviour. The wider effects of selection against post-mixing aggressiveness are discussed. Examining the behavioural strategies of unaggressive pigs, especially their response to defeat, would reveal how selection may alter aggressive tactics. Selection against lesions from mixing is also expected to reduce their number in more stable social conditions, but the implications for aggression between sows and that of sows towards their piglets and humans needs to be investigated. Aggressiveness is genetically correlated with response to handling involving components of social isolation, human presence and novelty. Identifying how unaggressive pigs respond to other challenging situations differing in these components may be worthwhile. Selection against aggression using skin lesions appears to be achievable although the full value of this would benefit from estimations of the genetic correlations with the traits outlined above.