Mixing at young ages reduces fighting in unacquainted domestic pigs

Burlap and buddies: the effects of social enrichment (preweaning mixing) and object enrichment (burlap) on piglet performance, behavior, and welfare in the preweaning environment

When weaned in commercial operations, piglets are not only separated from their sow but also mixed with unfamiliar pigs in an unfamiliar environment with a new diet. These abrupt changes can be stressful for piglets, often having negative welfare consequences. Our objective was to study the effects of early-life preweaning socialization and object enrichment in the preweaning environment. We compared piglet performance, behavior, and welfare across six treatments that combined multi-litter group size (1 vs. 2 vs. 4 litters) and burlap (yes vs. no). We recorded piglet behavior and lesion-scored sows and piglets. Normal conforming data, expressed per experimental unit (and behavior data were averaged over time), were analyzed by ANOVA. When given the opportunity in the sow barn, piglets in multi-litter groups socialized with other litters. Burlap use (P = 0.08) was observed in < 5% of the observations but tended to increase in mixed litter groups. Cross-sucking was observed in ~12% of the observations within mixed litter groups and tended to increase with mixed group size (P = 0.08). While there was no difference in the proportion of piglets nursing (P > 0.10), piglets were less active in the single crate groups and most active in the groups of two litters mixed (P = 0.03). Additionally, observed piglet/sow biting behaviors did not differ between treatments; however, piglet-piglet biting (P = 0.07), and pen object manipulation (P = 0.07) tended to be observed more frequently in non-enriched groups. Piglet displacements were observed more often in non-enriched groups around the pen (P = 0.03) but tended to be observed more often in enriched groups at the teat (P = 0.07). Preweaning socialization and object enrichment had no impact on the average number of piglets weaned per sow or total piglet mortality (P > 0.10). However, the proportion of laid-on piglets decreased as the number of mixed litters increased (P = 0.02). The average number of lesions per piglet did not differ between treatments. Although the final lesion scores of sow teat and udder condition did not differ between treatments (P > 0.10), sow udder scores tended to worsen more in the single litters than in the mixed litters (P = 0.08). Overall, social and object enrichment allows piglets to socialize at a younger age and to redirect their attention toward an object (burlap) which does not negatively impact piglet or sow performance, or behavior, and may improve piglet welfare around weaning.

Social Support in a Novel Situation Aimed for Stunning and Euthanasia of Pigs May Be Increased by Familiar Pigs-A Behavioural Study with Weaners

The common method of stunning pigs using high concentration carbon dioxide prior to slaughter poses an animal welfare issue, as the gas is aversive. Proof of concept for using nitrogen gas encapsulated in high-expansion foam as an alternative non-aversive method for stunning pigs has recently been presented. However, the individually tested pigs showed distress-related responses to foam exposure, regardless of whether it was nitrogen- or air-filled. This study examined the effect of companionship from a familiar or unfamiliar pig on behaviours in 72 nine-weeks old pigs during exposure to air-filled foam. Escape attempts were observed by 75% of solitary pigs, 42% of pigs with unfamiliar conspecifics, and 33% of pigs with familiar conspecifics. Familiar pig pairs clearly preferred social contact during foam exposure, whereas this was not as clear in unfamiliar pig pairs, and their motivation for social contact could have multiple explanations. The results from this study highlight the importance of contact with conspecifics when studying animal welfare and suggest that familiarity between pigs is important for social support, thus emphasizing the importance of maintaining social groups to reduce distress in pigs at slaughter.

Asinine milk mitigates stress-mediated immune, cortisol and behavioral responses of piglets to weaning: A study to foster future interventions in humans

Introduction

The present study assessed whether asinine milk supplementation improved the immune and behavioral responses of piglets during an early life weaning stress event as a model for its future use in humans.

Methods

For this, 48 piglets from 4 different litters were used. At 20 days of age, piglets were weighed and allocated with their litter and dam into group pens until 28 days of age. Four piglets from each litter were then randomly assigned to either (1) asinine milk supplementation (n = 16) (2), skimmed cow milk supplementation (n = 16) or (3) no supplementation (n = 16; control group). The supplementations were voluntarily administered for 3 days preweaning and 3 days postweaning using a baby bottle. The effects on the weaning stress response were assessed through salivary cortisol measurements; behavioral tests such as the open field, novel object end elevated plus maze tests; and gene expression of HSD11B1, NR3C1 and IL1B in PBMCs, which was determined by RT-qPCR and normalized to GAPDH and UBB. To test the effect of the supplementations on weight, milk intake, gene expression, and behavior, a randomized block design was used with repeated measurements over time by the PROC MIXED procedure.

Results and discussion

The effects on salivary cortisol were determined using the ratio between the morning and afternoon concentrations, considering the time before and after the weaning event. Principal component analysis (PCA) and Fisher's test were performed to evaluate the behavior test data. When comparing salivary cortisol concentrations between the pre- and postweaning periods, there was a difference (p < 0.05) between the supplementation groups in the afternoon period, suggesting that piglets fed asinine milk had lower afternoon cortisol concentrations postweaning than their counterparts. For the behavioral tests, the supplementations had no measurable effects. No difference was between groups pre- and postweaning for the expression of HSD11B2, which codes for an enzyme that breaks down cortisol. However, the expression of NR3C1, which encodes the glucocorticoid receptor, was significantly upregulated in piglets supplemented with cow milk (mean 1.245; p < 0.05).

Conclusion

Asinine milk downregulated 1L1B gene expression, which codes for an inflammatory cytokine. In conclusion, these results suggest that supplementation with asinine milk may represent a strategy to diminish the damage associated with an early life event by modulating IL1B expression and reducing salivary cortisol levels in piglets undergoing weaning stress. Further transcriptomic and metabolomic studies may improve our understanding of the molecular pathways that mediate this systemic immune-mediated response.

Investigating the effects of two weaning methods and two genetic hybrids on play behavior in weaner pigs (Sus scrofa)

In conventional pig production, suckling pigs are typically weaned between 3 and 5 weeks of age. This involves separation from the sow, dietary change, and regrouping in a novel environment, which challenge the welfare of pigs. We investigated the effects of two weaning methods [conventional weaning: two litters mixed in a weaner pen of different size and design (MOVE) vs. litter staying in the farrowing pen after removing the sow (STAY)] and two genetic hybrids [DanBred Yorkshire × Landrace (approximately 21 total pigs born/litter; DB) vs. Topigs Norsvin TN70 Yorkshire × Landrace (approximately 16 total pigs born/litter with higher individual birth weight and weaning weight than DB; TN)] on play behavior across weaning. Both genetic hybrids were inseminated with semen of DanBred Duroc boars. Litters were reduced to the number of functional teats at birth. The durations of locomotor-rotational play (LOC) and social play (SOC) of 24 indoor-housed litters [pigs/litter: (average ± SD) 13 ± 2; age at the weaning day: 26 ± 2 days] were video-recorded continuously between 14:00 h and 22:00 h on days −1, 1, and 2 relative to weaning and statistically analyzed with mixed-effects modeling at the individual level. Before weaning, TN pigs performed LOC longer than DB pigs. On day 2 post-weaning, STAY pigs engaged in more SOC than MOVE pigs. Moreover, TN pigs and STAY pigs displayed a steeper increase in LOC from days 1 to 2 than DB pigs and MOVE pigs, respectively. We demonstrated that pigs belonging to the genetic hybrid with higher weight at birth and weaning spent more time playing on the day before weaning. Additionally, weaning pigs in the farrowing pen and, hence, avoiding social mixing and relocation to an unfamiliar environment had a positive effect on social play after weaning. Our study illustrates that weaning stress in pigs may be reduced by using a genetic hybrid featuring higher birth and weaning weight and by keeping litters intact in a familiar environment after weaning. This study also supports the use of play behavior as an animal welfare indicator.

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.

A multi-suckling system combined with an enriched housing environment during the growing period promotes resilience to various challenges in pigs

Little is known about the impact of social and environmental enrichment on improving livestock resilience, i.e. the ability to quickly recover from perturbations. We evaluated the effect of an alternative housing system (AHS) on resilience of pigs, as compared to conventional housing (CONV). The AHS consisted of multi-litter housing during lactation, delayed weaning, extra space allowance and environmental enrichment at all times. We assessed recovery to a 2 h-transport challenge, an LPS injection, 2 h-heat stress and a biopsy wound in 96 pigs. Additionally, indicators of long-term “wear and tear” on the body were determined. AHS pigs had better physiological recoveries with quicker returns to baseline in the transport and LPS challenges, showed lower cortisol accumulation in hairs and lower variance in weight gain over the experimental period compared to conventionally-housed (CONV) pigs. They also had higher levels of natural antibodies binding KLH than CONV pigs. Their response to heat stress revealed a different strategy compared to CONV pigs. Taken together, AHS pigs appear to be more resilient and experience less chronic stress. Enhancing welfare by provision of social and environmental enrichment that better meets the behavioural needs of pigs seems to be a promising approach to improve their resilience.

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.

Mixing aggression intensity is associated with age at first service and floor type during gestation, with implications for sow reproductive performance

Aggression resulting from mixing to establish a dominance hierarchy is a major welfare concern for group-housed sows. The associated stress can negatively impact aspects of reproductive performance. Objectives of this study were to investigate associations between 1) age at first service (AFS) and mixing aggression intensity in first parity sows, 2) mixing aggression intensity and reproductive performance within and between parity one and parity two, and 3) mixing aggression intensity, floor type during gestation and reproductive performance. Gilts (n =160, hereafter referred to as sows) were mixed into stable groups of eight unfamiliar individuals approximately 4 days after artificial insemination, housed on fully slatted concrete (CON; n =80) floor uncovered or covered with rubber slat mats (RUB; n =80), and followed through two parities. Skin lesions (SLMIX; a proxy for the intensity of mixing aggression), were scored post mixing in each parity according to severity (0=no lesions to 5=severe lesions) on five body regions (ear, neck, hindquarter, rump, and belly) on the left and right sides, and at the tail/anogenital region. Total SLMIX score was calculated for each sow. Data on reproductive performance traits were acquired retrospectively from farm records for both parities. Two analyses were performed: 1) data from each parity were analysed separately and 2) SLMIX score in parity one was used to predict reproductive performance in parity two. Lower AFS was associated with a lower SLMIX score in parity one (P =0.031). There was no association between SLMIX score and reproductive performance in parity one, while sows with higher SLMIX score in parity two had a higher proportion of piglets dead during lactation (P =0.027) and a longer cycle length (P =0.003) in parity two. Sows with higher SLMIX scores in parity one had more non-productive days (P <0.001) in parity two. Concrete sows had a higher SLMIX score than RUB sows in parity one (P =0.015), but not in parity two. In addition, CON sows had a higher proportion of piglets born dead (P =0.013) compared with RUB sows in parity two. Mixing aggression has a negative influence on reproductive performance within parities, and it may also have a long-term negative carry-over effect on reproductive performance in subsequent parities. Serving gilts at younger ages could help to minimize the intensity of aggression at mixing, while housing on rubber flooring has beneficial implications for their reproductive performance.

Application of extended feed withdrawal time preslaughter and its effects on animal welfare and carcass and meat quality of enriched-housed pigs

A total of 144 barrows were distributed into four treatment groups. One group was housed conventionally and fasted for 16 h preslaughter, while the other three groups were housed in enriched conditions (straw-bedding and low density) and fasted for 16, 24 and 32 h preslaughter. When compared with conventionally-housed pigs, enriched-housed pigs were heavier (P < .05) and fatter (P < .01), but easier to handle at loading (P < .05) and produced less exudative pork (P < .05) possibly resulting from a lower post-mortem muscle glycolytic potential (P = .10). Extending fasting time up to 32 h reduced dressing yield (P < .001) and increased skin lesion scores (P < .01), but did not result in any clear or major effect on muscle metabolism and meat quality. In conclusion, given the beneficial effects of enriched housing conditions on stress response and pork quality, the application of an extended fasting time (32h) preslaughter is not required for this production.

The immediate effects of weaning stress on the hypothalamus-pituitary-adrenal alteration of newly weaned piglets

This study was conducted to examine the effects of weaning stress on gene expression of specific markers in hypothalamus-pituitary-adrenal (HPA) axis and neuronal activity in the newly weaned piglets. Twelve 28-days-old, newly weaned crossbred (Landrace × Yorkshire × Duroc) male piglets from 6 l (2 piglets/l) were randomly categorized into two groups: (a) weaning stress: piglets were separated from their dams, relocated and mixed with the unacquainted domestic piglets for 2 hr (stress, n = 6); (b) no-stress: piglets stayed with their dams in the farrowing house (NS; n = 6). After weaning stress, all piglets were electrically euthanized and the blood samples/HPA tissues were collected for subsequent analysis, including plasma cortisol and mRNA expression of c-fos, c-jun, corticotropin-releasing hormone (CRH), CRH receptor 1 (CRHR-1) and adrenocorticotropin hormone receptor (MC2R). Results: Weaning stress significantly (p < 0.05) increased the plasma cortisol level and suppressed the expression of c-fos and CRH in hypothalamus. In addition, weaning stress enhanced the mRNA abundance of c-jun and CRHR-1 in the pituitary gland. No significant differences in the gene expression of MC2R and CRHR-1 were observed in the adrenal gland between treatment groups. Taken together, HPA involved in weaning stress and CRHR-1 and c-jun could be potential markers to evaluate the activation of HPA axis.

Effects of Clostridium butyricum and Enterococcus faecalis on growth performance, immune function, intestinal morphology, volatile fatty acids, and intestinal flora in a piglet model

We investigated the effects of Clostridium butyricum and Enterococcus faecalis (probiotics) in a piglet model.

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

Simple Summary

Pig welfare is a societal concern, partly due to the intensive rearing conditions. One welfare concern is aggression between newly regrouped pigs. Aggression at weaning is reduced by putting several groups of piglets together when young; termed socialization. Information is missing about how socialization affects sow health and if the behavioural changes in piglets are long-lasting. We aimed to address these questions by studying sow udder quality and pig behaviour and growth in socialized and control groups. Pigs were socialized by either joining two litters (32 sows; 16 groups) at 14 days of age or not joining them (33 sows). At weaning, the sows of socialized groups had more udder damage than the controls. Socialized piglets had double the amount of bite injuries (skin lesions) than controls the day after socialization, but had 19% fewer skin lesions at regrouping at eight weeks old when injuries are more numerous and severe. At 11 weeks old, there was no difference between the groups. In a test for aggressiveness, socialized pigs attacked more often and quicker, showing greater confidence in agonistic skills. Socialization means additional work for farmers and may cause more udder damage, but has beneficial effects for pig behaviour and welfare at later regrouping.

Abstract

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

Social network properties predict chronic aggression in commercial pig systems

Post-mixing aggression in pigs is a harmful and costly behaviour which negatively impacts both animal welfare and farm efficiency. There is vast unexplained variation in the amount of acute and chronic aggression that dyadic behaviours do not fully explain. This study hypothesised that certain pen-level network properties may improve prediction of lesion outcomes due to the incorporation of indirect social interactions that are not captured by dyadic traits. Utilising current SNA theory, we investigate whether pen-level network properties affect the number of aggression-related injuries at 24 hours and 3 weeks post-mixing (24hr-PM and 3wk-PM). Furthermore we compare the predictive value of network properties to conventional dyadic traits. A total of 78 pens were video recorded for 24hr post-mixing. Each aggressive interaction that occurred during this time period was used to construct the pen-level networks. The relationships between network properties at 24hr and the pen level injuries at 24hr-PM and 3wk-PM were analysed using mixed models and verified using permutation tests. The results revealed that network properties at 24hr could predict long term aggression (3wk-PM) better than dyadic traits. Specifically, large clique formation in the first 24hr-PM predicted fewer injuries at 3wk-PM and high betweenness centralisation at 24hr-PM predicted increased rates of injury at 3wk-PM. This study demonstrates that network properties present during the first 24hr-PM have predictive value for chronic aggression, and have potential to allow identification and intervention for at risk groups.

Cross-Fostering Implications for Pig Mortality, Welfare and Performance

This study aimed to (1) identify cross-fostering (CF) practices employed on a commercial farm; (2) characterize CF pigs according to litter of origin traits, and (3) investigate the implications of CF practices on pig mortality, performance and welfare. This was an observational study whereby pigs were managed according to normal farming practice. Pigs (n = 1,016) born within 1 week were classified as non-CF (NCF); CF during the first (CFW1) and second or third (CFW2+) weeks of lactation. Pigs were individually weighed and inspected for the presence of tail (TL), ear (EL) and body lesions (BL) at weaning (7.03 ± 1.61 kg) and at the end of the first (12.9 ± 3.03 kg) and second (31.9 ± 5.50 kg) weaner and grower (66.3 ± 9.12 kg) stages. Mortality was recorded through to slaughter (c. 115 kg). At slaughter, TL were scored and carcass characteristics, presence of pleurisy, enzootic pneumonia, pericarditis and heart condemnations were recorded. 40.8% of CF pigs were CFW1; ANOVA tests revealed these were born to sows with a higher number of piglets born alive than NCF pigs (14.6 ± 2.61 and 12.8 ± 2.68, respectively). The remaining 59.2% of CF pigs were CFW2+; these were, on average, 0.14 kg lighter at birth than NCF pigs. Therefore, a nested case control design was retrospectively applied whereby pigs with complete records to slaughter, were matched for these variables to investigate associations between CF weeks, welfare and performance traits. Growth performance did not differ between CF week (P > 0.05); however, CFW2+ carcasses were 4.9 kg lighter (P < 0.05) compared with NCF and CFW1 pigs. EL were more likely in CFW1 compared to NCF and CFW2+ (P < 0.05) pigs. To investigate the effect of CF week on the risk of mortality, all 1,016 pigs were used. CF pigs were at higher risk of death (P < 0.05) with similar odds in CFW1 and CFW2+ pigs compared with NCF pigs, although other underlying factors could contribute to this result. Performance and health traits were similar between CF weeks. Early cross-fostering appeared to influence the presence of ear lesions but the mechanism is likely indirect and difficult to explain.

The early-life environment of a pig shapes the phenotypes of its social partners in adulthood

Social interactions among individuals are abundant, both in natural and domestic populations, and may affect phenotypes of individuals. Recent research has demonstrated that the social effect of an individual on the phenotype of its social partners may have a genetic component, known as an indirect genetic effect (IGE). Little is known, however, of nongenetic factors underlying such social effects. Early-life environments often have large effects on phenotypes of the individuals themselves later in life. Offspring development in many mammalian species, for example, depends on interactions with the mother and siblings. In domestic pigs, individuals sharing the same juvenile environment develop similar body weight later in life. We, therefore, hypothesized that offspring originating from the same early-life environment also develop common social skills that generate early-life social effects (ELSEs) that affect the phenotypes of their social partners later in life. We, therefore, quantified IGEs and ELSEs on growth in domestic pigs. Results show that individuals from the same early-life environment express similar social effects on the growth of their social partners, and that such ELSEs shape the growth rate of social partners more than IGEs. Thus, the social skills that individuals develop in early life have a long-lasting impact on the phenotypes of social partners. Early-life and genetic social effects were independent of the corresponding direct effects of offspring on their own growth, indicating that individuals may enhance the growth of their social partners without a personal cost. Our findings also illustrate how research devoted to quantifying IGEs may miss nongenetic and potentially confounded social mechanisms which may bias the estimates of IGEs.

Behaviour and performance of suckling gilts and their piglets in single housing with different fixation times

Abstract. The objective was to evaluate suckling performance and behaviour traits of gilts and piglets in two different single-housing farrowing systems under practical conditions. Performance data of 70 crossbred gilts and their 842 piglets were collected. The behavioural observation included 17 gilts and 211 piglets. Gilts of the control group (full-time crating, FTC) were fixed during farrowing and suckling (Pro Dromi® 1), and in the experimental group (short-time crating, STC) gilts were fixed for 6 days postpartum (p.p.) only (Pro Dromi® 1.5). Six farrowing crates were included in each group, and six replications were carried out. Performance data were collected and gilts' and piglets' behaviour was observed with 10 min scan samples and categorized by standing, walking (only in STC), sitting and lying (side and belly). The management and the housing systems were in accordance with the Tierschutz-Nutztierhaltungsverordnung (TierSchNutztV, 2017). No significant (p  >  0.05) differences between FTC and STC were found in piglets born alive (13.2 and 13.9, respectively), loss of piglets (1.4 and 1.55, respectively) and weaned piglets including cross-fostering (12.0 and 12.4, respectively). Piglet loss due to crushing was 0.6 (FTC) and 0.64 (STC), with no significant difference (p  >  0.05). Overall, 82.5 % of all piglets killed due to crushing were lost from farrowing to day 2 p.p. The daily gain of STC piglets was significantly higher than that of FTC piglets (205 g vs. 199 g, respectively; p  <  0.05) during the suckling period (3 weeks). Concerning gilts' behaviour, significant differences (p  ≤  0.05) were found in sitting duration only (FTC 5.8 % and STC 4.0 %, respectively). FTC piglets spent more time lying, sitting and standing (7.4 % vs. 4.4 %, 0.5 % vs. 0.4 %, 9.6 % vs. 8.4 %, respectively; p  ≤  0.05). The reason could be the higher acceptance of the piglet nest in STC. It was possible to conclude that gilts' welfare was improved by STC compared to FTC, and farrowing crates with loose single housing did not lead to higher piglet loss in the suckling period. An earlier end of the fixation period of the gilt at day 2 or 3 p.p. should be tested.

Causes, consequences and biomarkers of stress in swine: an update

BACKGROUND

In recent decades there has been a growing concern about animal stress on intensive pig farms due to the undesirable consequences that stress produces in the normal physiology of pigs and its effects on their welfare and general productive performance. This review analyses the most important types of stress (social, environmental, metabolic, immunological and due to human handling), and their biological consequences for pigs. The physio-pathological changes associated with stress are described, as well as the negative effects of stress on pig production. In addition an update of the different biomarkers used for the evaluation of stress is provided. These biomarkers can be classified into four groups according to the physiological system or axis evaluated: sympathetic nervous system, hypothalamic-pituitary-adrenal axis, hypothalamic-pituitary-gonadal axis and immune system.

CONCLUSIONS

Stress it is a process with multifactorial causes and produces an organic response that generates negative effects on animal health and production. Ideally, a panel of various biomarkers should be used to assess and evaluate the stress resulting from diverse causes and the different physiological systems involved in the stress response. We hope that this review will increase the understanding of the stress process, contribute to a better control and reduction of potential stressful stimuli in pigs and, finally, encourage future studies and developments to better monitor, detect and manage stress on pig farms.

[Effects of socializing piglets in lactation on behaviour, including tail-biting, in growing and finishing pigs]

OBJECTIVE

The aim of this study was to determine whether early socialising of piglets influences the later behaviour and the risk of tail biting in growing and finishing pigs.

MATERIAL AND METHODS

The behaviour of 183 animals (divided in three successive runs) was recorded from birth until the end of the fattening period. Furthermore, the condition of the teats of the sows as well as the integument and tails of the growing and finishing pigs were evaluated. To socialize the piglets, four litters of the experimental group (V) were provided with additional space (walkway) by opening "piglet-doors" (day 10 postpartum of the youngest litter). The piglets of the control group (K) were reared in conventional farrowing crates located in the same compartment of the stable. Post-weaning, the piglets were assigned to three groups: the experimental group (V/V, two litters of group V), the control group (K/K, two litters of group K) and the mixed group (V/K, one litter of group V and one litter of group K).

RESULTS

After opening the "piglet-doors", piglets of group V displayed significantly more playing behaviour than piglets of group K. Additionally, the agonistic behaviour increased in group V. Post-weaning, at allocation and mixing, animals of group V/V showed significantly less agonistic behaviour than pigs of group K/K. Tail-biting behaviour occurred in all three groups, but only in runs two and three. On the 100th day of the fattening period, 58.7% of the pigs of group V/V, 51.7% of group V/K and 43.3% of group K/K still had intact tails. In pigs of group K/K, the tails were significantly shorter compared to the other two groups.

CONCLUSION AND CLINICAL RELEVANCE

Early socialization enhances piglet welfare in farrowing pens by encouraging playing behaviour. Less agonistic behaviour at allocation could furthermore reduce stress at mixing and allocation. The aim to reduce the incidence of tail-biting could not be achieved. However, socializing piglets in lactation could contribute, in accordance with other measures, to an influence on biting behaviour.

Effects of Mixing on the Aggressive Behavior of Commercially Housed Pigs

In this study, we investigated the effects of mixing on the aggressive behavior of commercially housed pigs. The behavioral patterns of 36 groups of pigs (a total of 360 animals) were observed over 3 consecutive days directly after weaning (25±1.2 days of age), and 25 and 50 days later with the aid of video technology. Fight latency and total duration and frequency of fighting were significantly different among the age groups. The aggressive behaviors decreased in 75-day old pigs if compared to 25- and 50-day old animals. Moreover, dominance index (DI) was higher in 25-day old and lower in 75-day old pigs. A comparison of dominant (DI>0) and submissive (DI<0) pigs showed significant differences (p<0.05) for major aggressive behaviors in all age groups. Dominant pigs were involved in more aggressive interactions, had longer fights, and initiated more fights than submissive pigs. Post-mixing aggressive behavior was altered by previous experience of mixing. Aggressive behavior and DI are suitable methods for analyzing the effects of mixing on commercially housed growing pigs.

Social stress as a cause of diseases in farm animals: Current knowledge and future directions

Over the past 50 years, biomedical research has established a strong linkage between psychosocial stress and disease risk in humans, which has transformed the understanding of stress and the role it plays in human lives. This research has led to personalized medicine where a reduction in daily life stress is a main goal for many people with debilitating illnesses. This review describes the supporting evidence that social stress also plays a critical role in farm animal disease prevention, and may be a mediator by which common management practices can increase disease risk. There is evidence that social factors, including deprivation of social contact ('social isolation'), reducing space allowance ('crowding') and disturbing social order ('social instability') trigger physiological and behavioral indicators of stress in livestock. Less research exists, however, linking management practices that trigger social stress with higher disease risk. Suggestions are offered for future research opportunities, and practical, evidence-based recommendations are made for reducing the negative effects of social isolation, instability and crowding. The current evidence that social factors contribute to disease risk in farm animals is not as convincing as the human literature, but remains a promising and important area for future research.

Does the environmental background (intensive v. outdoor systems) influence the behaviour of piglets at weaning?

Under intensive pig husbandry, outdoor systems offer a more complex physical and social environment compared with indoor systems (farrowing sheds). As the rearing environment affects behavioural development, it can, therefore, influence behavioural responses of pigs to stressful environments in later stages of production. We tested how the rearing environment influenced behavioural responses to a novel arena test in piglets on the day that they were weaned and mixed into large groups. We recorded video footage and compared the behavioural responses of 30 outdoor-raised and 30 farrowing shed-raised piglets tested in an experimental arena and sequentially exposed to four challenges (each for 5 min) on the day of weaning. Quantitative and qualitative behavioural measures were recorded using time budgets and scoring demeanour or 'qualitative behavioural expression' (using Qualitative Behavioural Assessment (QBA)). When held in isolation (challenge 1), both groups were scored as more 'scared/worried', while outdoor-raised piglets spent more time eating and jumping against the arena walls. Both groups interacted with a plastic ball (challenge 2: exposure to a novel object) during which they were scored as more 'playful/curious' than other challenges. When a food bowl was introduced (challenge 3), farrowing shed-raised piglets were more interested in playing with the food bowl itself, whereas outdoor-raised piglets spent more time eating the feed. Finally, there were no significant differences in social behaviour (challenge 4: introduction of another piglet) between the two groups in terms of the latency to contact each other, amount of time recorded engaged in aggressive/non-aggressive social interactions or QBA scores. Although piglets spent 30% of their time interacting with the other piglet, and half of this time (47%) was engaged in negative interactions (pushing, biting), the levels of aggression were not different between the two groups. Overall, outdoor-raised piglets ate more and were scored as more 'calm/passive', whereas farrowing shed-raised piglets spent more time investigating their environment and were scored as more 'playful/inquisitive'. In conclusion, we did not find differences in behaviour between outdoor-raised and farrowing shed-raised piglets that would highlight welfare issues. The differences found in this study may reflect conflicting affective states, with responses to confinement, neophobia and motivation for exploration evident.

Animal health, welfare and production problems in organic weaner pigs

This paper reviews the available information on the different health and animal welfare issues in organic pigs in relation to weaning. It addresses the most relevant health and welfare problems and reviews their potential hazards and associated risk factors. Regarding health, problems related to post weaning diarrhoea, cold stress, skin lesions, endoparasites and post weaning multisystemic wasting syndrome are described. Reasons for distress and frustration in weaned piglets are identified as mainly separation from the mother, a new environment, mixing and fear of humans. Finally, hazards and risk factors for health and welfare in organic weaners are related to animal characteristics, housing systems, feed/nutrition and management. Generally, it is concluded that diseases around weaning are multifactorial in nature, with several factors contributing simultaneously as stressors at the time of weaning. In order to solve problems around weaning, the complexity and the individuality of farm systems need to be taken into account.

Effects of ractopamine administration and castration method on the response to preslaughter stress and carcass and meat quality in pigs of two Piétrain genotypes

The objective of this study was to evaluate the effects of ractopamine supplementation, castration method, and their interaction on the behavioral and physiological response to preslaughter stress and carcass and meat quality of 2 Piétrain genotypes. A total of 1,488 male pigs (115 ± 5 kg BW) were distributed according to a 2 × 2 × 2 factorial arrangement of treatments. The first factor was ractopamine supplementation with 2 groups of pigs (376 and 380 pigs each) receiving 7.5 mg/kg of ractopamine (RAC) or not (NRAC) in their diet during the last 28 d of the finishing period. The second factor was castration method, with 744 surgical castrates (SC) and 744 immunized males (IM), and the third factor was the genotype with 2 crossbreeds containing 50% (genotype A, GA; n = 744) or 25% (genotype B, GB; n = 744) Piétrain genetics. Surgical castration took place at 2 d of age, whereas immunization against gonadotropin-releasing factor (GnRF) was performed through 2 subcutaneous injections of GnRF analog (Improvest, 2 mL) at 10 and 4 wk before slaughter. At loading more vocal stimulation was needed by the handler to drive GB pigs forward through the farm alley (P = 0.01) and RAC-fed GB pigs through the ramp (P = 0.02). Feeding RAC to IM increased the number of fights in lairage compared with SC (P = 0.03). Feeding RAC shortened fighting bouts compared with NRAC pigs (P = 0.05). The SC-GA pigs showed a greater gastrointestinal tract temperature during unloading (P = 0.05) and lairage time (P = 0.03). Blood creatine kinase (CK) concentrations were greater (P = 0.04) in SC compared with IM, and no difference was found in the concentrations of stress hormones in urine collected postmortem. Dressing yield was greater (P = 0.01) in RAC and SC-GB pigs. Carcasses from RAC pigs and IM were leaner than those from NRAC and SC pigs (P < 0.001 and P = 0.002, respectively). Feeding RAC to IM increased drip loss in the LM (P = 0.05). Warner-Bratzler shear force values were slightly greater in the LM from RAC-GB pigs and from IM compared with SC (P = 0.01 and P < 0.001, respectively) and in the semimembranosus muscle of RAC pigs (P = 0.006). In conclusion, immunization against GnRF more than the use of Piétrain genotypes appears to be a viable alternative to the use of ractopamine, as it seems to promote production of lean carcasses without compromising animal welfare and pork quality.

Sorting by parity to reduce aggression toward first-parity sows in group-gestation housing systems

Young sows are subordinate and vulnerable in group-housing systems because they usually lose most fights and suffer more injuries than mature sows at mixing. This study was conducted to evaluate effects of sorting by parity on reducing aggression and associated stress with the aim to improve welfare and performance of first-parity sows in a group-housed system. Sows and gilts (n = 180) from 6 breeding groups were used. Within each group, 2 groups of 15 females were mixed in each of 2 treatment pens after weaning and remained there throughout the entire gestation period. The control pen consisted of 11 multiparous and 4 first-parity sows, and the treatment pen consisted of 11 gilts and 4 first-parity sows. Before mixing and at the end of the gestation period, sows and gilts were weighed individually, assessed for BCS, and measured for backfat thickness. Injury scores were assessed before and 48 h after mixing and wean-to-mating intervals, farrowing rate, and litter performance at the subsequent farrowing were recorded for all females. Aggressive interactions involving first-parity sows were video recorded for 72 h immediately after mixing in each pen. Data were analyzed using the Glimmix procedure of SAS with a Poisson regression model for count data and a Gaussian model for continuous data. All females in treatment pens sustained fewer scratches (P = 0.01) after mixing than females in control pens. First-parity sows in treatment pens fought more frequently (P = 0.01), tended to fight for longer periods (P = 0.08), and won more fights (P = 0.04) of parallel pressing but had fewer injures (P = 0.03) after mixing, gained more BW (P = 0.01) during gestation, and had greater farrowing rates (P = 0.03) compared with first-parity sows in control pens. The results suggest that sorting by parity shielded first-parity sows from severe injuries caused by mixing-induced aggression so that their welfare and performance can be improved in group housing systems.

Drinking behavior in nursery pigs: determining the accuracy between an automatic water meter versus human observers

Assimilating accurate behavioral events over a long period can be labor-intensive and relatively expensive. If an automatic device could accurately record the duration and frequency for a given behavioral event, it would be a valuable alternative to the traditional use of human observers for behavioral studies. Therefore, the objective of this study was to determine the accuracy in the time spent at the waterer and the number of visits to the waterer by individually housed nursery pigs between human observers scoring video files using Observer software (OBS) and an automatic water meter Hobo (WM, control) affixed onto the waterline. Eleven PIC USA genotype gilts (22 +/- 2 d of age; 6.5 +/- 1.4 kg of BW) were housed individually in pens with ad libitum access to a corn-based starter ration and one nipple waterer. Behavior was collected on d 0 (day of weaning), 7, and 14 of the trial using 1 color camera positioned over 4 attached pens and a RECO-204 DVR at 1 frame per second. For the OBS method, 2 experienced observers recorded drinking behavior from the video files, which was defined as when the gilt placed her mouth over the nipple waterer. Data were analyzed using nonparametric methods and the general linear model and regression procedures in SAS. The experimental unit was the individual pen housing 1 gilt. The GLM model included the method of observation (WM vs. OBS) and time (24 h) as variables, and the gilt nested within method was used as the error term. Gilts consumed more water (P = 0.04) on d 14 than on d 0. The time of day affected (P < 0.001) the number of visits and the time spent at the waterer regardless of the method. However, the OBS method underestimated (P < 0.001) the number of visits to the waterer (3.48 +/- 0.33 visits/h for OBS vs. 4.94 +/- 0.33 for WM) and overestimated (P < 0.001) the time spent at the waterer (22.6 +/- 1.46 s/h for OBS vs. 13.9 +/- 1.43 for WM) compared with WM. The relationship between the 2 methods for prediction of time spent at the waterer and number of visits made by the gilts was weak (R(2) = 0.56 and 0.69, respectively). Collectively, these data indicate that the use of the traditional OBS method for quantifying drinking behavior in pigs can be misleading. Quantifying drinking behavior and perhaps other behavioral events via the OBS method must be more accurately validated.

Socializing piglets before weaning: effects on behavior of lactating sows, pre- and postweaning behavior, and performance of piglets

This study evaluated how socializing piglets before weaning affects behavior of lactating sows and the pre- and postweaning behavior and performance of piglets. Two farrowing rooms, each with 6 pens, and 1 nursery with 4 pens were used. In total, data were obtained from 24 sows and their litters. In each farrowing room, the solid barriers between 3 farrowing pens were removed on d 12 after farrowing, and the sows remained confined in their crates (experimental group). In the other 3 farrowing pens of each farrowing room, sows and their litters were kept under conventional conditions until weaning (control group). All piglets were weaned 28 d after birth. After weaning, piglets from each group remained together in 1 pen of the nursery. The behavior of sows (lying, standing, sitting, nursing) and piglets (lying, active, suckling) in the farrowing rooms was observed for 24 h before and for 48 h after removal of the barriers between the pens. In addition, behavior (active, lying, feeding, agonistic behavior) of piglets was observed in the nursery during the initial 48-h period after weaning. Each piglet was weighed on d 5, 12, and 28 after birth and thereafter weekly until the fifth week of rearing. In the farrowing room, mixing of litters did not influence behavior of piglets and sows. Preweaning weight gain of the piglets did not differ (P = 0.60) between the treatments. In the initial 48 h after weaning, less agonistic behavior (P < 0.001) was observed in piglets belonging to the experimental group. During 5 wk of rearing, piglets in the experimental group gained more weight compared with the control group (P = 0.05). The advantage shown by the experimental group became especially conspicuous in the first week after weaning (P = 0.05). By socializing unfamiliar piglets before weaning, stress due to mixing could at least be distanced in time from the other burdens of weaning, thereby improving performance.

Effect of drinker type on water intake and waste in newly weaned piglets

During the first few days after weaning, pigs often experience BW loss as they adapt to eating solid food. During this time period, they are also known to drink excessively and develop abnormal oral behavior such as belly nosing. The excessive drinking may stem from the piglets' attempt to satiate hunger through gut fill from a familiar ingestive source. Gut fill through water intake may affect the establishment of feeding behavior. Using drinker devices other than the standard nipple drinker may ease the piglets' transition at weaning by facilitating the initiation of feeding and preventing the development of behavioral problems such as excessive drinking and belly nosing. In this experiment, we examined the effect of drinker type on water and food intake, growth rates, and belly nosing in newly weaned piglets. Eighteen pens of 15 piglets each (270 piglets total) were weaned at 18.1 +/- 0.1 d of age and housed in pens containing 1 of 3 drinker devices (standard nipple, push-lever bowl, and float bowl). Piglets' water and feed intake, water use, BW, and behavior were examined on a pen basis through 2 wk after weaning. Piglets with nipple drinkers wasted more water than the other piglets (P < 0.001; float, 295 +/- 70 mL x pig(-1) . d(-1); nipple, 1,114 +/- 63 mL x pig(-1) . d(-1); and push-lever, 186 +/- 63 mL x pig(-1) . d(-1)), whereas piglets with float bowls consumed less water than the other piglets (P < 0.001; float, 475 +/- 81 mL . pig(-1) x d(-1); nipple, 870 +/- 76 mL x pig(-1) . d(-1); push-lever, 774 +/- 76 mL x pig(-1) . d(-1)). Drinker type affected feeding behavior (P = 0.02); piglets with push-lever bowls spent less time at the feeder than the other piglets, although no difference was detected for feed intake (P = 0.64) or overall ADG (P = 0.16). Piglets with push-lever bowls also tended to perform less piglet-directed nosing behavior than piglets with the float bowl (P = 0.04). Piglets appear to use more water during the first 2 d after weaning with certain drinker devices. However, piglets do not appear to attain satiety through water consumption because most of the water used during the first few days after weaning is wasted. This excessive drinking and water wastage can be abated through the use of push-lever drinkers without negative implications for feed intake or growth rates.