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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.

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.

Lameness in dairy cattle is a persistent problem, indicating pain caused by underlying disease states and is associated with reduced milk yields. Digital dermatitis is a common cause of lameness. Thermal imaging is a technique that may facilitate early detection of this disease and has the potential for use in automated detection systems. Previous studies with thermal imaging have imaged either the heels or the coronary band of the foot and typically only used the maximum temperature (Max) value as the outcome measure. This study investigated the utility of other statistical descriptors: 90th percentile (90PCT), 95th percentile (95PCT), standard deviation (SD) and coefficient of variation (CoV) and compared the utility of imaging the heel or coronary band. Images were collected from lame and healthy cows using a high-resolution thermal camera. Analyses were done at the cow and foot level. There were significant differences between lame and healthy feet detectable at the heels (95th percentile: P < 0.05; SD: P < 0.05) and coronary band (SD: P < 0.05). Within lame cows, 95PCT values were higher at the heel (P < 0.05) and Max values were higher at the coronary band (P < 0.05) in the lame foot compared to the healthy foot. ROC analysis showed an AUC value of 0.72 for Max temperature and 0.68 for 95PCT at the heels. It was concluded that maximum temperature is the most accurate measure, but other statistical descriptors of temperature can be used to detect lameness. These may be useful in certain contexts, such as where there is contamination. Differentiation of lame from healthy feet was most apparent when imaging the heels.

In this study, we aimed to validate existing plasma assays to measure biomarkers for maternal signalling in milk and saliva of lactating sows. These biological samples are minimally invasive to the animal and could give a physiological profile of maternal qualities available to their piglets. Sows were farrowed in a zero-confinement system, and their colostrum and milk samples were manually collected during naturally occurring let-downs (i.e. not induced) over the lactation period. Saliva sampling involved sows voluntarily accepting cotton buds to chew without restraint. Commercial kits designed for blood plasma were tested, and any modifications and results are given. We successfully measured total protein, cortisol, tumour necrosis factor-α (TNF-α) and oxytocin in pig milk and saliva and immunoglobulin G (IgG) in pig milk samples. We were unsuccessful at measuring relaxin and serotonin in these biological samples. We observed higher levels of biomarkers in milk than in saliva. The measurement of TNF-α in pig milk for the first time revealed increased levels with larger litters. This development will allow more detailed understanding of biomarkers in milk. There was also evidence that the minimally invasive technique of using saliva sampling did not interrupt natural oxytocin production around parturition.

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.

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

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

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

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

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

The objective of the study was to estimate genetic correlations between skin lesions and aggressive behavior postmixing and under more stable social conditions as a potential means of selecting against pig aggressiveness. Postmixing aggression in commercial pig production is common, compromises welfare and profitability, and cannot be significantly reduced by low-cost changes to the environment. A genetic component to individual aggressiveness has been described in pigs and other species. Selective breeding against aggressiveness ought to be possible if an easily measured indicator trait can be shown to be genetically associated with aggressive behavior. Aggressive behavior was recorded continuously for 24 h after mixing, and a count of skin lesions (lesion count, LC) was recorded at 24 h and 3 wk postmixing on 1,663 pigs. Two behavioral traits were found to have a moderate to high heritability similar to that of growth traits; duration of involvement in reciprocal fighting (0.43 +/- 0.04) and delivery of nonreciprocal aggression (NRA; 0.31 +/- 0.04), whereas receipt of NRA had a lower heritability (0.08 +/- 0.03). Genetic correlations (r(g)) suggested that lesions to the anterior region of the body 24 h after mixing were associated with reciprocal fighting (r(g) = 0.67 +/- 0.04), receipt of NRA (r(g) = 0.70 +/- 0.11), and to a lesser extent, delivery of NRA (r(g) = 0.31 +/- 0.06). Lesions to the center and rear were primarily genetically associated with receipt of NRA (r(g) = 0.80 +/- 0.05, 0.79 +/- 0.05). Genetic correlations indicated that pigs that engaged in reciprocal fighting delivered NRA to other animals (r(g) = 0.84 +/- 0.04) but were less likely to receive NRA themselves (r(g) = -0.41 +/- 0.14). A genetic merit index using lesions to the anterior region as one trait and those to the center or rear or both as a second trait should allow selection against animals involved in reciprocal fighting and the delivery of NRA. Positive correlations between LC 24 h and 3 wk after mixing were found, especially for lesions to the center and rear of the body, indicating that postmixing lesions are predictive of those received under more stable group conditions. As well as reducing immediate aggression at mixing, selection on postmixing LC is expected to have a long-term impact on injuries from aggression, even after dominance relationships are established.

Survival is reduced in low birth weight piglets, which display poor thermoregulatory abilities and are slow to acquire colostrum. Our aim was to identify additional behavioural and physiological indicators of piglet survival incorporating traits reflective of both the intrauterine and extrauterine environment. Data were collected from 135 piglets from 10 Large White x Landrace sows to investigate which physiological measurements (e.g. individual placental traits), and which behavioural measurements (e.g. the quantification of piglet vigour), were the best indicators of piglet survival. Generalised linear models confirmed piglet birth weight as a critical survival factor. However, with respect to stillborn mortality, piglet shape and size, as measured by ponderal index (birth weight/(crown-rump length)(3)), body mass index (birth weight/(crown-rump length)(2)), respectively, and farrowing birth order were better indicators. With respect to live-born mortality, postnatal survival factors identified as crucial were birth weight, vigour independent of birth weight, and the latency to first suckle. These results highlight the importance of the intrauterine environment for postnatal physiological and behavioural adaptation and identify additional factors influencing piglet neonatal survival.