Impact of prenatal stress and environmental enrichment prior to weaning on activity and social behaviour of piglets ( Sus scrofa )

Review: Early life piglet experiences and impacts on immediate and longer-term adaptability

Pigs in production systems are routinely exposed to challenging situations including abrupt weaning, painful husbandry procedures, intense contact with stockpeople, and exposure to novel social and physical environments. The resilience of pigs to these stressors has implications for animal welfare and productivity and can be affected by early life experiences. In rodents and primates, early experiences with stressors that the animal can adequately cope with confers future stress adaptability, leading to less abnormal behaviour, lower behavioural and physiological responses to stressors, and faster recovery after stress exposure. Early experiences that can affect the ability of pigs to overcome challenge include interactions with the dam, conspecifics, humans, and the overall complexity of the environment. Farrowing crates limit the sow's ability to show maternal behaviour towards piglets, and negatively affect piglet social behaviour during lactation, with less play and more manipulation of pen mates in crates than in large pens. Rearing in pens has been proposed to improve the ability of pigs to cope with routine stressors, but the evidence for this is conflicting. The early housing environment can affect general fearfulness and fear of humans, and surprisingly, most studies have shown fear responses to be greater in pigs reared pens than in crates. Given the potential for fear to affect animal welfare and productivity, more detailed research on early housing effects is needed. While there is limited evidence that early housing influences fear in the longer term, human contact early in life appears to have a more profound and sustained effect, with regular positive human interaction early in life having an enduring effect on reducing pigs' fear of humans. The practicality of positive human-pig interaction in a commercial environment needs to be examined further, but only a small amount of positive human contact early in life can improve the resilience of pigs to routine husbandry stressors. Early social experience with non-littermates reduces stress at weaning and mixing, while early weaning before 3-4 weeks of age increases abnormal behaviours. Environmental enrichment, such as foraging substrates and increased floor space, reduces abnormal behaviour in piglets, but housing in an enriched environment early in life and subsequently in a non-enriched environment can increase abnormal behaviour if these environments are dramatically different. Although the later environment can modify the influence of the early environment, overall, early life experiences can be important in shaping how pigs cope with stress in both an immediate and longer-term capacity.

Early human contact and housing for pigs - part 1: responses to humans, novelty and isolation

The development of fear and stress responses in animals can be influenced by early life experiences, including interactions with humans, maternal care, and the physical surroundings. This paper is the first of three reporting on a large experiment examining the effects of the early housing environment and early positive human contact on stress resilience in pigs. This first paper reports on the responses of pigs to humans, novelty, and social isolation. Using a 2 × 2 factorial design, 48 litters of pigs were reared in either a conventional farrowing crate (FC) where the sow was confined or a loose farrowing pen (LP; PigSAFE pen) which was larger, more physically complex and allowed the sow to move freely throughout the farrowing and lactation period. Piglets were provided with either routine contact from stockpeople (C), or routine contact plus regular opportunities for positive human contact (+HC) involving 5 min of scratching, patting and stroking imposed to the litter 5 days/week from 0-4 weeks of age. The positive handling treatment was highly effective in reducing piglets' fear of humans, based on +HC piglets showing greater approach and less avoidance of an unfamiliar person at 3 weeks of age. There was evidence that this reduction in fear of humans lasted well beyond when the treatment was applied (lactation), with +HC pigs showing greater approach and less avoidance of humans in tests at 6, 9 and 14 weeks of age. The +HC treatment also reduced piglets' fear of a novel object at 3 weeks of age, and for pigs in FC, the cortisol response after social isolation at 7 weeks of age. Rearing in FC compared to LP reduced piglets' fear of novelty at 3 weeks of age, as well as their vocalisations and cortisol response to isolation at 7 weeks of age. The FC pigs showed greater approach and less avoidance of humans compared to LP pigs at 3, 4 and 6 weeks of age, but not at 9 and 14 weeks of age. These results show that positive handling early in life can reduce pigs' fear of humans, fear of novelty and physiological stress response to social isolation. The LP pigs were reared in a more isolated environment with less overall contact with stockpeople and other pigs, which may have increased their fear responses to humans and novel situations, suggesting that different housing systems can modulate these pigs' responses.

The effect of providing a greater freedom of movement through periodic exercise on the welfare and stress physiology of stall-housed gestating sows and on piglet behaviour

In Canada, the 2014 Code of Practice for the Care and Handling of Pigs proposed the continued operation of existing stall barns after 2024 on condition that bred sows be given access to periodic exercise. Therefore, this study evaluated the effects of periodic exercise on sow welfare. Sows (n = 180) were assigned to one of three treatments: stall-housed (Control: C); stall-housed and exercised weekly for 10 min (Exercise: E); and group-housed (Group: G). Sow postures and stereotypies were recorded once per week in early, mid and late gestation before (AM) and after (PM) exercise. Female piglets (n = 168 from C, E and G sows) underwent isolation and novel object tests at 19–22 days of age. Postures differed by treatment in AM with G sows lying more and sitting less than C and E sows, which did not differ. In PM, E sows sat more than G sows, with C sows being intermediate. In early gestation, G sows performed fewer stereotypies than E sows, with C sows being intermediate. In mid gestation, G sows performed fewer stereotypies than C and E sows, which did not differ. Piglets from C sows were more active in the novel object test than E and G piglets, which did not differ. Group housing improved sow comfort (indicated by postures) and reduced sow stress (indicated by stereotypies), but periodic exercise did not. Decreased activity level in piglets from sows given greater freedom of movement indicates that gestation housing can influence the behaviour of offspring.

Welfare of pigs on farm

This scientific opinion focuses on the welfare of pigs on farm, and is based on literature and expert opinion. All pig categories were assessed: gilts and dry sows, farrowing and lactating sows, suckling piglets, weaners, rearing pigs and boars. The most relevant husbandry systems used in Europe are described. For each system, highly relevant welfare consequences were identified, as well as related animal-based measures (ABMs), and hazards leading to the welfare consequences. Moreover, measures to prevent or correct the hazards and/or mitigate the welfare consequences are recommended. Recommendations are also provided on quantitative or qualitative criteria to answer specific questions on the welfare of pigs related to tail biting and related to the European Citizen's Initiative 'End the Cage Age'. For example, the AHAW Panel recommends how to mitigate group stress when dry sows and gilts are grouped immediately after weaning or in early pregnancy. Results of a comparative qualitative assessment suggested that long-stemmed or long-cut straw, hay or haylage is the most suitable material for nest-building. A period of time will be needed for staff and animals to adapt to housing lactating sows and their piglets in farrowing pens (as opposed to crates) before achieving stable welfare outcomes. The panel recommends a minimum available space to the lactating sow to ensure piglet welfare (measured by live-born piglet mortality). Among the main risk factors for tail biting are space allowance, types of flooring, air quality, health status and diet composition, while weaning age was not associated directly with tail biting in later life. The relationship between the availability of space and growth rate, lying behaviour and tail biting in rearing pigs is quantified and presented. Finally, the panel suggests a set of ABMs to use at slaughter for monitoring on-farm welfare of cull sows and rearing pigs.

Improving maternal welfare during gestation has positive outcomes on neonatal survival and modulates offspring immune response in pigs

Improving the housing of pregnant sows by giving them more space and access to deep straw had positive effects on their welfare, influenced their maternal behavior and improved the survival of their offspring. The present study aimed at determining whether these effects were actually due to environmental enrichment and whether the provision of straw pellets and wood can partly mimic the effects of straw bedding during gestation. Three graded levels of enrichment were used, that were, collective conventional pens on slatted floor (C, n = 26), the same pens with manipulable wood materials and distribution of straw pellets after the meals (CE, n = 30), and larger pens on deep straw litter (E, n = 27). Sows were then housed in identical farrowing crates from 105 days of gestation until weaning. Decreased stereotypies, blood neutrophils, and salivary cortisol, and increased behavioral investigation indicated that health and welfare of sows during gestation were improved in the E environment compared with the C environment. The CE sows responded as C or E sows depending on the trait. Piglet mortality rate in the first 12 h after birth was lower in E and CE litters than in C litters, but enrichment level during gestation had only small effects on lactating sow behavior and milk composition postpartum. On days 2 and 3 of lactation, E sows interrupted less often their nursing sequences than C and CE sows. On day 2, milk from both E and CE sows contained more minerals than that from C sows. In one-day-old piglets, the expression levels of genes encoding toll-like receptors (TLR2, TLR4) and cytokines (interleukin-1, -6 and -10) in whole blood after 20-h culture, were greater in E piglets than in CE or C piglets. In conclusion, housing sows in an enriched environment during gestation improved early neonatal survival, probably via moderate and cumulative positive effects on sow behavior, milk composition, and offspring innate immune response. The gradation in the effects observed in C, CE and E housing environment reinforced the hypothesis of a causal relationship between maternal environmental enrichment, sow welfare and postnatal piglet 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.

Risk Factors for Chronic Stress in Sows Housed in Groups, and Associated Risks of Prenatal Stress in Their Offspring

Chronic stress has a detrimental effect on sow welfare and productivity, as well as on the welfare and resilience of their piglets, mediated prenatally. Despite this, the specific risk factors for chronic stress in pregnant sows are understudied. Group-housed pregnant sows continuously face numerous challenges associated with aspects of the physical (group type and size, flooring, feeding system) and social (stocking density, mixing strategy) environment. There are many well-known potent stressors for pigs that likely contribute to chronic, physiological stress, including overcrowding, hot temperatures, feed restriction, inability to forage, uncomfortable floors, and poor handling. Some of these stressors also contribute to the development of production diseases such as lameness, which in turn are also likely causes of chronic stress because of the associated pain and difficulty accessing resources. The aim of this review is to discuss potential risk factors for chronic stress in pregnant sows such as space allowance, group size and type (stable/dynamic), feeding level, lameness, pen design, feed system, enrichment and rooting material, floor type, the quality of stockmanship, environmental conditions, and individual sow factors. The mechanisms of action of both chronic and prenatal stress, as well as the effects of the latter on offspring are also discussed. Gaps in existing research and recommendations for future work are outlined.

Early environmental enrichment prevents cognitive impairments and developing addictive behaviours in a mouse model of prenatal psychological and physical stress

Environmental enrichment (EE) has shown remarkable effects in improving cognition and addictive behaviour. We tested whether EE could help recover from prenatal stress exposure. Mature Swiss Webster male and virgin female mice were placed together until vaginal plugs were detectable. Next, pregnant rodents were randomized into the control, physically and psychologically stressed groups. The application of stress was initiated on the 10th day of pregnancy and persisted for a week to induce stress in the mice. Open field and elevated plus-maze (EPM) tests were utilized as explorative and anxiety assays, respectively. A passive avoidance shuttle-box test was carried out to check anxiety-modulated behaviour. Morris water maze (MWM) test was undertaken to evaluate spatial learning and memory. Conditioned place preference (CPP) test was selected for evaluation of tendency to morphine consumption. Our results showed that prenatal stress elevated anxiety-like behaviour in the offspring which EE could significantly alleviate after weaning. We also found a higher preference for morphine use in the physical stress and psychological stress offspring group. However, no difference was observed among the genders. Application of EE for the stress group improved several parameters of the cognitive behaviour significantly. Although prenatal stress can lead to detrimental behavioural and cognitive outcomes, it can in part be relieved by early exposure to EE. However, some outcomes linked to prenatal stress exposure may not be diminished by EE therapy. In light of such irreversible effects, large-scale preventive actions promoting avoidance from stress during pregnancy should be advised.

Genetic variation in LUMAN/CREB3 and association with stress and meat quality traits in Yorkshire pigs

LUMAN/CREB3 is a stress regulatory gene that affects the activity of the hypothalamic–pituitary–adrenal axis in mice and presents a promising avenue for exploring variable stress-responsiveness in pigs. Pigs with similar characteristics to LUMAN-deficient mice, including greater resilience to stress and receptivity to human handling, would be valuable in the pork industry from animal welfare and production efficiency perspectives. We previously identified eight genetic variations and five haplotypes throughout the LUMAN locus in Yorkshire pigs. In this study, we analysed associations between LUMAN variations with behavioural stress response during three tests (open field test, novel object test, and human approach test), physiological stress responsiveness (cortisol), and carcass/meat quality measurements from purebred Yorkshire pigs. Haplotypes A1 and A2 were associated with decreased activity levels in novel environments and greater plasma cortisol concentrations at slaughter. Haplotype A1 was associated with lower carcass scratch scores and meat with lower cooking losses and greater tenderness. Haplotypes B1 and B2 were associated with the opposite traits including increased activity levels in novel environments and characteristics for lower meat quality including greater cooking losses, lower marbling, and paler coloured meat. We conclude that DNA variations in the LUMAN locus could potentially be used as genetic markers for stress resistance and meat quality in pig breeding.

Cost-Effectiveness Analysis of Seven Measures to Reduce Tail Biting Lesions in Fattening Pigs

Tail biting is an important animal welfare issue in the pig sector. Studies have identified various risk factors which can lead to biting incidents and proposed mitigation measures. This study focused on the following seven key measures which have been identified to affect the risk of tail biting lesions: improvements in straw provision, housing ventilation, genetics, stocking density, herd health, provision of point-source enrichment objects, and adoption of early warning systems. The aim of this study was to examine whether these selected measures to reduce the risk of tail biting lesions in pig fattening are cost-effective. The problem was analyzed by first summarizing the most prospective interventions, their costs and expected impacts on the prevalence of tail biting lesions, second, by using a stochastic bio-economic model to simulate the financial return per pig space unit and per pig at different levels of prevalence of tail biting lesions, and third by looking at how large a reduction in tail biting lesions would be needed at different levels of initial prevalence of lesions to cover the costs of interventions. Tail biting lesions of a severity which would require an action (medication, hospitalization of the pig or other care, or taking preventive measures) by the pig producer were considered in the model. The results provide guidance on the expected benefits and costs of the studied interventions. According to the results, if the average prevalence of tail biting lesions is at a level of 10%, the costs of this damaging behavior can be as high as €2.3 per slaughtered pig (~1.6% of carcass value). Measures which were considered the least expensive to apply, such as provision of point-source enrichment objects, or provided wider production benefits, such as improvements in ventilation and herd health, became profitable at a lower level of efficacy than measures which were considered the most expensive to apply (e.g., straw provision, increased space allowance, automated early warning systems). Measures which were considered most efficient in reducing the risk of tail biting lesions, such as straw provision, can be cost-effective in preventing tail biting, especially when the risk of tail biting is high. At lower risk levels, the provision of point-source objects and other less costly but relatively effective measures can play an important role. However, selection of measures appropriate to the individual farm problem is essential. For instance, if poor health or barren pens are causing the elevated risk of tail biting lesions, then improving health management or enriching the pens may resolve the tail biting problem cost-effectively.

Social status and previous experience in the group as predictors of welfare of sows housed in large semi-static groups

Mixing gestating sows implies hierarchy formation and has detrimental consequences on welfare. The effects of social stress on the most vulnerable individuals may be underestimated and it is therefore important to evaluate welfare between individuals within groups. This study aimed at investigating the impact of social status and previous experience in the group on well-being of sows housed in large semi-static groups. We assessed aggression (d0 (mixing), d2, d27, d29), body lesions (d1, d26, d84) and feeding order on 20 groups of 46–91 animals. Social status was based on the proportion of fights won during a 6-hr observation period between d0 and d2. Dominants (29%) were those who won more fights than they lost, Subdominants (25%) won fewer fights than they lost, Losers (23%) never won any fight in which they were involved while Avoiders (23%) were never involved in fights. Resident sows (70%) were already present in the group in the previous gestation while New sows (30%) were newly introduced at mixing. Subdominants and Dominants were highly involved in fights around mixing but this was more detrimental for Subdominants than Dominants, Losers and Avoiders since they had the highest body lesion scores at mixing. Avoiders received less non-reciprocal agonistic acts than Losers on d2 (P = 0.0001) and had the lowest body lesion scores after mixing. However, Avoiders and Losers were more at risk in the long-term since they had the highest body lesions scores at d26 and d84. They were followed by Subdominants and then Dominants. New sows fought more (P<0.0001), tended to be involved in longer fights (P = 0.075) around mixing and had more body lesions throughout gestation than Resident sows. Feeding order from one-month post-mixing was influenced both by the previous experience in the group and social status (P<0.0001). New sows, especially with a low social status, are more vulnerable throughout gestation and could serve as indicators of non-optimal conditions.

Like Mother Like Child: Do Fearful Sows Have Fearful Piglets?

Gestational and early life experiences affect subsequent behavioural and physical development. The objective of the current study was to investigate associations between gilts' fear of humans, gestational stress level, and feeding and maternal behaviour, as well as how these related to aspects of the personality and growth of their offspring. A total of 37 gilts were used. Four human approach tests were performed between d 104 and d 111 of gestation to classify gilts as fearful or friendly. Gilt feeding behaviour and salivary cortisol concentration was measured between d 90 and d 108 of gestation, and gilt nursing behaviour assessed at d 13 of lactation. Piglets were subject to a back test at d 13 of age, to an open field test and a human approach test at d 20 of age, and growth was monitored to weaning (d 26 of age). Gilts classified as having a fearful behavioural profile had higher cortisol levels than friendly gilts (p < 0.05). Human fear level did not affect reproductive performance or the growth of offspring (p > 0.05). The offspring of friendly gilts tended to have a more active response to the back test (p = 0.09), less freezing response in the open field test (p < 0.05), and received human contact more than piglets from fearful gilts (p < 0.05). The present study shows that gilt human fear level is linked to their stress levels, which can affect the personality of their piglets.

The Role of Genetic Selection on Agonistic Behavior and Welfare of Gestating Sows Housed in Large Semi-Static Groups

Simple Summary

Group-housing of gestating sows is becoming increasingly common worldwide as it offers the sows the opportunity to exercise, display exploratory behaviors, and develop social relationships. Despite its advantages, group-housing as it stands in modern industries also presents several welfare issues such as overt aggression between pen-mates and resulting stress and injuries. To date, breeding companies often largely focused their efforts on genetic selection based on individual production characteristics (e.g., litter size, piglets’ growth, and meat quality) and traditionally ignored the social behaviors and the ability to establish a dominance hierarchy without exacerbated aggression. Hence, the extent to which agonistic behavior differs according to new genetic lines is unknown. The objective of this study was to compare and investigate the influence of two genetic lines on the welfare and performance of sows housed in large semi-static groups (up to 91 animals). While the first genetic line was more aggressive toward pen-mates during gestation, the second had piglets with a lower robustness and survivability. This study raises the difficulty of finding an optimal genetic line, including both positive welfare and productivity outcomes, and points to the urgent need of considering social aspects when developing genetic lines for group-housing.

Abstract

Confinement of gestating sows is becoming banished in favor of group-housing in countries worldwide, forcing breeding companies to develop genetic lines adapted for social living. This study aimed at assessing the influence of two genetic lines selected for high performance (HP1, HP2, derived from Landrace × Yorkshire) on welfare and reproductive performance of sows housed in large semi-static groups (20 groups of 46–91 animals) across several parities. To address this, agonistic behaviors were recorded on d0, d2, d27, and d29 post-mixing while body lesions were scored on d1, d26, and d84. Sows’ individual and reproductive performances were also recorded. HP2 sows were more aggressive than HP1 sows since they fought (p = 0.028) and bullied (p = 0.0009) pen-mates more frequently on d0–d2. HP2 sows had more total body lesions throughout gestation than HP1 sows at higher parities (p < 0.0001). Regarding reproductive performance, HP2 sows lost less piglets (p < 0.0001) and tended to wean more piglets (p = 0.067) than HP1 sows. In conclusion, while HP2 sows were the most aggressive, HP1 sows had piglets with lower survivability, which raises ethical issues in both cases and points to the need of considering social aspects when developing genetic lines for group-housing.

A High Enrichment Replenishment Rate Reduces Damaging Behaviors and Increases Growth Rate in Undocked Pigs Kept in Fully Slatted Pens

One of the difficulties in complying with the prohibition of routine tail docking is a lack of effective alternative solutions to prevent tail biting, especially in fully slatted systems. This study compared three slat-compatible enrichment replenishment strategies for pigs. Forty-eight mixed-sex pens (six males and six females/pen) of undocked pigs were followed from birth to slaughter. Pre-weaning, half the pigs were provided with enrichment materials (a cardboard cup, rubber toy, hessian cloth and bamboo), in addition to a rope for the sows, in all farrowing crates. Post-weaning, all pens were enriched with eight identical items, including an elevated rack supplied with fresh-cut grass, and objects of wooden, bamboo, rubber, and fabric materials presented in various ways. However, three different replenishment frequencies were applied: "Low" (replenished on Monday/Wednesday/Friday), "Medium" (replenished once daily), and "High" (replenished ad libitum). Individual pigs were weighed on days 0, 49, 91, and 113 post-weaning. Direct behavior observations were conducted twice weekly at pen level (10 min/day/pen), and tail and ear lesion scores of individual pigs were also recorded every other week. These measurements were taken during the post-weaning period. The cost of all enrichment materials used was calculated. Pre-weaning enrichment only contributed to a lower ear lesion score (P = 0.04). No difference in lesion scores was found between post-weaning treatments. "Low" replenishment rate pigs performed more damaging behaviors (tail/ear biting, belly-nosing, mounting, other biting, and aggressive behaviors combined) than "High" and "Medium" pigs (P < 0.01). The average daily gain in the finishing stage was higher in "High" than "Low" pigs (P < 0.05). Although sporadic tail biting occurred, only 0.69% of the pigs had their tails bitten severely enough that they became shorter than half of a normal undocked tail. The average enrichment cost for the post-weaning period was <€2 per pig. In conclusion, the high enrichment replenishment rate increased growth and reduced damaging behaviors compared to the low replenishment rate pigs. Overall, these findings show that the provision and regular replenishment of multiple, slat-compatible, enrichment sources can reduce tail damage to manageable levels without the need for tail docking.

Does Diversity Matter? Behavioural Differences between Piglets Given Diverse or Similar Forms of Enrichment Pre-Weaning

Simple Summary

This study looked at behavioural differences between piglets provided with either two identical or two different enrichment materials. From seven days-old until weaning, piglets were given hessian fabrics or bamboo: the control group had only hessian, and the diverse groups had both hessian and bamboo. One object was attached to the pen wall and the other suspended in the middle of the pen and piglets behaviours were observed. Objects suspended in the middle of the pen attracted more attention than objects attached to the wall. Piglets preferred hessian over bamboo, and the interest in hessian increased over time, while interest in bamboo remained unchanged. Piglets interacted differently with the objects: more oral manipulation and shaking occurred with the hessian and more pushing occurred with the bamboo. Control piglets performed more biting than piglets with diverse enrichment, both pre- and post-weaning. Therefore, providing different forms of enrichment to piglets pre-weaning has the potential to reduce biting occurrences and, thus, to promote welfare. Hessian was probably favoured because it allowed oral manipulation, which was the most frequent interaction observed.

Abstract

This study investigated the behavioural effects of providing different enrichment materials to suckling piglets from 7 days-old until weaning. One object was attached to the pen wall (WALL), and the other was suspended in the middle of the pen (MID). Control group had the hessian fabric in both locations, and the two diverse groups had hessian and bamboo stick in alternate locations (i.e., BMID-HWALL and HMID-BWALL). Piglets behaviour was recorded on D0 (object introduction), D1, D5, D8, D12, and D14; at weaning and 1, 3, 5 and 15 days after. Groups did not differ in approaching or interacting with objects on D0. MID objects attracted more attention than WALL objects (p < 0.01). Piglets interacted more with hessian than bamboo (p < 0.001). They performed more oral manipulation and shaking with hessian (p < 0.001), but more pushing of bamboo (p < 0.001). Interactions with objects increased with time (p < 0.001), especially with hessian (p < 0.01), while interest in bamboo remained unchanged. Control piglets performed more biting than piglets with diverse enrichment (pooled data), both pre- and post-weaning (p < 0.05). Therefore, providing different types of enrichment material can reduce biting behaviour pre- and post-weaning. Hessian was favoured, possibly because this was easier to bite and shake, which were the behaviours most often observed.

Risk factors associated with tail damage in conventional non-docked pigs throughout the lactation and rearing period

Tail biting is an abnormal behaviour in pigs, and remains an economic and welfare problem in modern pig production. Reasons for performing tail-biting behaviour are of multifactorial origin, and are often related to the current environment or internal characteristics of pigs. The objective of the present study was to identify early life risk factors connected to tail damage in non-docked pigs in a commercial Danish piggery, and to further compare the effects of cumulative cross-life experience throughout the early rearing. In an observational study, 741 piglets from 51 sows born in six batches were individually marked at birth and followed until nine weeks of age. Litter related variables and individual piglet characteristics were collected during lactation. The pigs' performance parameters were recorded from birth to nine weeks of age. The association between putative risk factors and tail damage assessed at different stages during lactation and rearing was analysed using multinomial mixed regression models. Prior to weaning, the odds of having tail damage were higher for piglets originating from litters with a high birth weight variation (P = 0.012) and for piglets that were heavier at weaning (P < 0.001). Piglets born to an aggressive sow had 2.7-fold increased odds of having tail damage (P = 0.003), while piglets of sows treated after farrowing had a lower odds (P = 0.015). Post-weaning, the most significant risk factor(s) associated with tail damage was the previous tail status of the pigs. Pigs with bite marks/ scratches in previous assessments had an on average 4-fold and pigs with a tail wound 11-fold increased odds of having tail damage during subsequent assessments. Similarly, pigs with a tail wound pre-weaning had 7-times higher odds of having tail damage at the end of rearing (P = 0.033). Pigs in groups with a higher weight variation (P = 0.030) and pigs with a greater weight gain (P < 0.001) had higher odds of having tail damage at the end of rearing. There was an increased chance of having tail damage post-weaning for piglets that were cross-fostered (P = 0.032) or that had a clinical impairment (P = 0.047) during lactation. Females generally had a lower chance of having tail damage compared to castrated males. Early life risk factors were especially associated with tail damage in pigs pre-weaning. However, the results of this study suggest that early life risk factors are secondary to the previous tail status of pigs as risk factors for later tail damage.

A longitudinal study of pre- and post-weaning tail damage in non-docked pigs

Tail-biting occurs pre-weaning, but literature on tail damage during lactation and on the development of damage over time is sparse, especially for non-docked piglets. We assessed the prevalence of tail damage in non-docked piglets in a commercial Danish piggery during the lactation and weaning period, and investigated the within-animal association of tail lesions pre- and post-weaning. Non-docked piglets (n = 741) from 51 loose-housed sows were individually marked and tracked from birth to 9 weeks (w9) of age. Tail damage was scored during lactation at w1 and w4, and once a week post-weaning (average weaning age 30 days) at w6 to w9. The within-animal association of tail damage before and after weaning was investigated at pig level using generalized mixed models. Tail damage was prevalent already pre-weaning. During the lactation period, the prevalence of tail lesions was 5% at w1 and 42% at w4, with the most prevalent score being 'superficial damages' (66.7%, score 1; pre-weaning scheme: 0 = no damage, 3 = tail wound). Post-weaning, 45% of pigs had a tail lesion at least once over the four assessments, with 16.7% of pigs having a tail lesion at least at two assessments. The majority of lesions were 'minor scratches' (34.2%, score 1; post-weaning scheme: 0 = no damage, 4 = wound - necrotic tail end) and a 'scabbed wound' (19.9%, score 3). The number of pigs with lesions as well as wound severity increased over time. More pigs had a tail wound at w8 (15%, P < 0.001 and < 0.01) and w9 (19%, P < 0.001 and < 0.001) compared to w6 (2.7%) and w7 (5.6%). Pigs with tail lesions pre-weaning (w1: OR 3.0, 95% CI 0.9 to 10.2; w4: OR 3.4, 95% CI 2.0 to 5.8) had a significantly higher risk of having a wound post-weaning, and pigs with lesions at w4 additionally were at a higher risk (OR 3.0, 95% CI 1.8 to 5.1) of having a lesion over several assessments. Females compared to castrated males had a significantly lower risk of having tail lesions at w1 (OR 0.3, 95% CI 0.1 to 0.8). Similarly, females were at a significantly lower risk (OR 0.5, 95% CI 0.4 to 0.9) of having a wound post-weaning, and tended to have a lower risk of having lesions over several assessments (OR 0.7, 95% CI 0.5 to 1.2). Our study confirmed that tail damage is prevalent already during the lactation period, and that pre-weaning tail damage is predictive of tail wounds post-weaning.

Pigs Like It Varied; Feeding Behavior and Pre- and Post-weaning Performance of Piglets Exposed to Dietary Diversity and Feed Hidden in Substrate During Lactation

Timely intake of solid feed is essential to ease the nutritional change from sow's milk to solid feed at weaning and thereby to reduce weaning-related problems. A significant percentage of piglets, however, do not or hardly consume solid feed before weaning. We studied effects of dietary variety and presenting the feed in substrate during lactation on the feeding behavior and performance of piglets up to 2 weeks post-weaning. Feed was provided ad libitum from d4 in two feeders, with four bowls each. In a 2 × 2 arrangement, 40 litters received either creep feed as a monotonous diet (MO) or four feed items simultaneously, i.e., creep feed, celery, cereal honey loops and peanuts, as a diverse diet (DD) and the feed was either provided without (CON) or with substrate (SUB), i.e., sand, in one of the two feeders up to weaning. Dietary diversity highly stimulated feed exploration and eating (≥2.5 times), feed intake and the percentage of (good) eaters from early in lactation, and enhanced piglet growth toward weaning (by 29 g/d), although MO-piglets spent more time eating creep feed from d18. Within MO, SUB-litters consisted of more good eaters than CON-litters. At weaning (d28) four piglets from the same treatment were grouped (n = 40 pens). DD-CON had the highest post-weaning feed intake and gain between d5–15 and the lowest proportion of pigs with higher tail damage scores. However, effects regarding behavior remained inconclusive, as DD-piglets had a lower and higher number of body lesions at 4 h and d15 post-weaning, respectively, spent less time exploring the feed(er) and drinker and environment, and more time nosing pen mates than MO-piglets. SUB-piglets showed a reduction in total post-weaning feed intake, gain (particularly between d0–2) and inactivity, increased levels of manipulation and aggression at week 1 and a higher number of body lesions at 4 h and d15 post-weaning. In conclusion, dietary diversity seems a promising feeding strategy in getting piglets to eat during lactation. Provision of substrate in the feeder subtly stimulated foraging behavior, but negatively impacted post-weaning adaptation, probably because treatments were not reinforced after weaning and piglets thus experienced loss of enrichment.

Effects of Environmental Enrichment on Pig Welfare-A Review

Good husbandry conditions on farms is of key importance for assuring animal welfare. One of the most important legal documents regulating the rules of maintaining pigs is the Directive 2008/120/EC, which states that group-housed pigs should have access to litter or other materials that provide exploration and occupation. Released in 2016, the Commission Recommendation (EU) 2016/336 on the application of the Council Directive 2008/120/EC characterizes the various categories of materials that may be used to improve animal welfare. According to the document, straw is considered as an optimal material for pig housing, however, materials categorized as suboptimal (e.g., wood bark) and materials of marginal interest (e.g., plastic toys) are often used in practice and scientific research. As such, the aim of this paper is to review and systematize the current state of knowledge on the topic of the impact of environmental enrichment on pig welfare. This article raises mainly issues, such as the effectiveness of the use of various enrichment on the reduction of undesirable behavior-tail biting; aggression; and stereotypies at the pre-weaning, post-weaning, and fattening stage of pig production.

Evaluating the Effects of In Utero Heat Stress on Piglet Physiology and Behavior Following Weaning and Transport

The study objective was to determine whether in utero heat stress (IUHS) affects piglet physiology and behavior following common production practices. A total of 12 gilts were confirmed pregnant and allocated to either heat stress (HS; n = 6) or thermoneutral (TN; n = 6) conditions on day 30⁻60 of gestation. At weaning (22.5 ± 2.3 days of age), 1 boar and 1 barrow of median weight were selected from each litter and transported for approximately 7 h. Piglets were then blocked into pens (n = 2/pen) by in utero treatment (IUHS (n = 12) or in utero thermoneutral (IUTN, n = 12)) and sexual status (boar (n = 6/in utero treatment) or barrow (n = 6/in utero treatment)). Plasma cortisol, non-esterified fatty acids (NEFA), insulin and glucose were evaluated 1 day prior to transport (pre-transport) and immediately after transport (post-transport). Behavioral data were collected on day 1⁻7 for 60 min at four different time points each day. In utero heat stressed piglets exhibited reduced cortisol concentrations compared to IUTN piglets immediately post-transport (p = 0.04). Glucose concentrations were not affected by in utero treatment. Insulin concentrations were reduced in IUTN piglets post-transport compared to pre-transport (p = 0.002), but no differences were detected for IUHS pigs. Non-esterified fatty acids tended to be reduced overall for IUHS vs. IUTN pigs (p = 0.08). Overall, IUHS piglets performed more drinking behaviors (p = 0.02) and tended to perform more aggressive behaviors (p = 0.07) than IUTN piglets in the 7 days post-transport. In summary, there was some evidence for altered physiological and behavioral responses among IUHS piglets compared to IUTN piglets following weaning and transport.

PHYSIOLOGY SYMPOSIUM: Postnatal consequences of in utero heat stress in pigs

Postnatal heat stress negatively impacts pig productivity and well-being as animals attempt to manage the resultant strain response. This is especially true when postnatal heat stress is combined with production stressors (e.g., mixing, weaning, transport, handling, and isolation) that have the potential to increase disease occurrence, morbidity and mortality. While pigs can utilize adaptive physiological mechanisms to compensate, these are often unfavorable to efficient livestock production. Specifically, postnatal heat stress decreases weight gain, reduces growth and production efficiency, alters carcass composition, and increases morbidity and mortality. Consequently, decreased animal performance constrains profitability and affects economic sustainability. In addition to the negative effects of postnatal heat stress, prenatal heat stress has long-term consequences that may compromise future piglet well-being and performance. Pigs gestated under heat stress conditions have an increased postnatal stress response and an increase in maintenance energy requirements. Furthermore, prenatal heat stress decreases swine birth weight, and increases teratogenicity, core body temperature set-point, and alters postnatal body composition (more adipose tissue and less skeletal muscle). Taken together, the effects of heat stress during pre- and postnatal pig development negatively influences productivity and well-being, a scenario that threatens the sustainability of global swine production.