Effects of stocking density and environmental enrichment on behavior and fecal corticosteroid levels of pigs under commercial farm conditions

Effect of lairage time prior to slaughter on stress in pigs: a path analysis

BACKGROUND

Pre-slaughter process during transportation, handling, and lairage causes stress in pigs, affecting animal welfare and meat quality. Therefore, lairage factors are important for relieving stress. A total of 24 LYD (Landrace × Yorkshire × Duroc) barrows were used to investigate the effect of 6 and 20 h lairage time (LT) on cortisol, serotonin, and catecholamine in blood and physiological factors in muscle, and to verify the causal relationship between these factors.

RESULTS

The results revealed that cortisol was increased (0.064 ± 0.007 µg/ml), and epinephrine (0.020 ± 0.002 µg/ml) and norepinephrine (1.518 ± 0.071 µg/ml) were lower at a LT of 20 h than those at 6 h, and there was no significant effect on the muscle and carcass characteristic factors. In addition, cortisol and norepinephrine showed a negative correlation (r = -50,346, p = 0.0121), epinephrine and glycogen had a positive correlation (r = 0.4417, p = 0.0307), and serotonin and heat shock protein 70 (HSP70) were positively correlated (r = 0.4715, p = 0.0200). Path analysis indicated that the increase in LT had a direct effect on cortisol, epinephrine, and norepinephrine, and an indirect effect on muscle glycogen.

CONCLUSION

This study confirmed the effect of the increase in LT from 6 to 20 h in the lairage room on the stress response of pigs. These findings support the legal requirements that advocate for shorter lairage times, in alignment with enhanced animal welfare standards.

Identification of intestinal and fecal microbial biomarkers using a porcine social stress model

Understanding the relationships between social stress and the gastrointestinal microbiota, and how they influence host health and performance is expected to have many scientific and commercial implementations in different species, including identification and improvement of challenges to animal welfare and health. In particular, the study of the stress impact on the gastrointestinal microbiota of pigs may be of interest as a model for human health. A porcine stress model based on repeated regrouping and reduced space allowance during the last 4 weeks of the finishing period was developed to identify stress-induced changes in the gut microbiome composition. The application of the porcine stress model resulted in a significant increase in salivary cortisol concentration over the course of the trial and decreased growth performance and appetite. The applied social stress resulted in 32 bacteria being either enriched (13) or depleted (19) in the intestine and feces. Fecal samples showed a greater number of microbial genera influenced by stress than caecum or colon samples. Our trial revealed that the opportunistic pathogens Treponema and Clostridium were enriched in colonic and fecal samples from stressed pigs. Additionally, genera such as Streptococcus, Parabacteroides, Desulfovibrio, Terrisporobacter, Marvinbryantia, and Romboutsia were found to be enriched in response to social stress. In contrast, the genera Prevotella, Faecalibacterium, Butyricicoccus, Dialister, Alloprevotella, Megasphaera, and Mitsuokella were depleted. These depleted bacteria are of great interest because they synthesize metabolites [e.g., short-chain fatty acids (SCFA), in particular, butyrate] showing beneficial health benefits due to inhibitory effects on pathogenic bacteria in different animal species. Of particular interest are Dialister and Faecalibacterium, as their depletion was identified in a human study to be associated with inferior quality of life and depression. We also revealed that some pigs were more susceptible to pathogens as indicated by large enrichments of opportunistic pathogens of Clostridium, Treponema, Streptococcus and Campylobacter. Generally, our results provide further evidence for the microbiota-gut-brain axis as indicated by an increase in cortisol concentration due to social stress regulated by the hypothalamic-pituitary-adrenal axis, and a change in microbiota composition, particularly of bacteria known to be associated with pathogenicity and mental health diseases.

Review: Space allowance for growing pigs: animal welfare, performance and on-farm practicality

There is considerable variation in the recommended minimum space allowance for growing pigs in scientific literature, and growing pressure, arising from recent reviews of current animal welfare standards for pigs, to increase the minimum space allowances set in legislation in some countries (e.g., European Union countries and New Zealand). The space provided for growing pigs needs to accommodate their physical body size in addition to social behaviour, activity, and essential functional behaviours. However, recommended minimum space allowances vary according to criteria such as temperature, live weight, flooring type, group size, behaviour, and enrichment availability. Though there may be justification for increasing current space requirements, this will present a practical issue on existing farms and could even result in unintended negative welfare outcomes, depending on how farmers address an increased requirement for space. This is not helped by inconsistent scientific approaches to assessing the effect of space on pig performance, and a lack of information on how space allowance impacts a pig's affective state. This review explores the scientific basis of the most common approaches to determining minimum space allowances for growing pigs and discusses the various factors that influence and interact with their spatial requirements. Consideration is given to their nutrition, physical environment, health, and behaviour to understand the welfare, performance, and practicality implications of differing recommendations for space allowance. More research is needed that investigates a range of space allowances to better understand the relationship between animal welfare and performance outcomes, and space allowance. This must replicate commercial conditions so that recommendations are relevant, future-focused, and achieve positive welfare outcomes in a practical but meaningful manner.

Blood transcriptomic differences in the immune response under stressful environmental according to stocking density in pigs

The implementation of animal welfare in the pig industry is becoming a global trend, and welfare can be improved through livestock management. In modern and intensive farming systems, it has become important to find a reasonable compromise between stocking density and productivity. The simultaneous detection of behavioral and physiological parameters is helpful when considering welfare levels for stocking density. This study aimed to confirm the effect of stocking density through transcriptome linkage. A comparison of three groups according to stocking density (low density, eight pigs and 1.0 m2 per head; normal density, eight pigs and 0.8 m2 per head; and high density, eight pigs and 0.6 m2 per head) was performed, and their transcriptomic changes were observed using the RNA-Seq method. Differentially expressed genes were identified for each comparison group (low density vs. normal density, 95 upregulated genes and 112 downregulated genes; high density vs. normal density, 133 upregulated genes and 217 downregulated genes; and high density vs. low density, 245 upregulated genes and 237 downregulated genes). Biological mechanisms according to stocking density were identified through functional annotation. T-cell differentiation and immune disease pathway enriched in the high-density group caused immune imbalance through dysregulated T-cell signaling. Moreover, oxidative stress, together with DNA damage, can lead to high susceptibility to disease. Our study confirmed the biological mechanisms through immunological expression patterns according to stocking density. The study results are expected to provide comprehensive insight into systematic operation strategies considering stocking density and biomarkers for use in welfare evaluation.

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.

Effects of Saccharomyces boulardii Supplementation on Nutritional Status, Fecal Parameters, Microbiota, and Mycobiota in Breeding Adult Dogs

Simple Summary

The aim of this study was to evaluate the effect of the administration of Saccharomyces boulardii on the nutritional, immunological, inflammatory, stress status, and the gut composition in 25 healthy adult American Staffordshire Terrier dogs. Supplementation with S. boulardii significantly improved the intestinal status and induced a reduction of stress, a common condition affecting animals managed in a breeding environment.

Abstract

The aim of this study was to evaluate the effect of the administration of Saccharomyces boulardii on the nutritional, immunological, inflammatory, and stress status and on the composition of the gut microbiota and mycobiota in healthy adult dogs. A total of 25 American Staffordshire Terrier dogs were selected and randomly assigned to two groups: control (CTR, n = 12) and treated (TRT, n = 13) groups. No significant differences were found between the two groups regarding body weight, body condition score, and fecal score. No significant differences in microbiota/mycobiota, short chain fatty acids, indole/skatole, histamine, zonulin, or lactoferrin were detected. Indeed, supplementation with S. boulardii significantly decreased fecal calprotectin Immunoglobulin A, indicating an improvement in the gut well-being. Interestingly, fecal cortisol significantly decreased in dogs belonging to the TRT group compared to the CTR, suggesting both an improvement of the intestinal status and a reduction of stress, a common condition affecting animals managed in a breeding environment.

Survey on the Past Decade of Technology in Animal Enrichment: A Scoping Review

Simple Summary

Enrichment is important for supporting the well-being of captive animals. Enrichment increase animal quality of life through encouraging natural behaviours. As enrichment is shifting to a more centered role in animal care, technology is becoming increasingly accessible and is becoming embedded in animal enrichment in creative ways. This review explores the trends in technology usage in animal enrichment studies. Through pulling the past decade of technology enrichment work together, we discuss gaps such as needing to include a larger variety of species (extending passed mammals), ensuring enrichment designs focus primarily on the senses an animal uses to interact with the world rather than human senses, and encouraging similar study designs across animal contexts to allow for streamlined comparisons.

Abstract

Environmental enrichment is adding complexity to an environment that has a positive impact on a captive animal as a necessity of care. Computing technology is being rapidly weaved throughout the space in both enrichment devices as well as evaluating enrichment outcomes. In this article, we present a scoping review of 102 captive animal enrichment studies and propose a contextual lens for exploring current practices. We discuss the importance of directed growth in species inclusion, transitioning beyond anthro-centric designs, and utilizing shared methodologies.

Effects of Enrichment Type, Presentation and Social Status on Enrichment Use and Behavior of Sows—Part 2: Free Access Stall Feeding

Simple Summary

The Canadian pork industry is transitioning to group housing gestation. The Code of Practice for pigs recommends the provision of enrichment. Although straw is considered prime enrichment, it is perceived as a biosecurity risk and manure management issue; therefore, identifying other enrichment materials is needed to promote adequate welfare. Previously, our group examined the effects of four types of point-source enrichments in an Electronic Sow Feeding (ESF) system. This study is a continuation of our previous research applied in Free Access Stalls (FAS). Four treatments were studied: (1) Constant: constant provision of wood on chain; (2) Rotate: rotation of three enrichments (rope, straw, and wood on chain); (3) Stimulus: rotation of three enrichments with an associative stimulus (bell or whistle); and (4) Control: no enrichment. Contact with enrichment and time spent in different postures were measured using scan sampling. Skin lesions were scored, and salivary cortisol was measured in a subset of dominant and subordinate sows. Sows spent more time contacting straw compared to other types of enrichment. There was no difference in enrichment use between dominant and subordinate sows, no increase in cortisol concentrations in subordinates nor significant differences in aggression. In conclusion, sows preferred straw enrichment and FAS provided some protection against aggression and stress.

Abstract

Continuing with previous research by our group in an ESF system, four types of enrichment treatments were assessed in gestating sows housed in Free Access Stalls: (1) Constant: constant provision of wood on chain; (2) Rotate: rotation of rope, straw and wood; (3) Stimulus: rotation of enrichments with an acoustic cue; and (4) Control: no enrichment. Treatments had a 12 day-duration. Four groups (28 ± 2 sows) were studied from weeks 6 to 14 of gestation. Groups received all treatments in random order. Three dominant and 3 subordinates per pen were selected using a feed competition test. Digital photos were collected at 10 min intervals for 8 h on days 1, 8, 10 and 12 to record interactions with enrichment. Skin lesions were assessed on days 1 and 12, and salivary cortisol was assessed in weeks 6, 10 and 14 of gestation. More enrichment use was observed in Rotate and Stimulus treatments compared to Constant, and more sows contacted enrichment when straw was provided in the Rotate and Stimulus treatments. There was no difference in the amount of enrichment use by dominants and subordinates, no cortisol concentration elevation in subordinate sows nor any difference in lesion scores. In conclusion, social status had little impact and feeding system is important to reduce stress and aggression.

Effect of Enrichment Items on the Physiology and Behavior of Sows in the Third Trimester of Pregnancy

Modern intensive pig breeding harms animal welfare, which is especially noticeable for pregnant sows kept in confinement stalls. This study aimed to evaluate the effects of enrichment items on the movement and physiological parameters of sows in the third trimester of pregnancy. A total of 30 large white pregnant sows were randomly divided into three equal treatment groups (n = 10): control, pine wood, and scented wood groups. Interestingly, compared with the control group, the sows in the pine wood or scented wood groups showed less ventral lying and more lateral lying behavior (p < 0.01), coupled with significant reduction in the frequency of scratching and sham-chewing (p < 0.01), but with no significant difference in the degree of preference for these enrichment items (p > 0.05). Additionally, the sows in the pine wood or scented wood groups also decreased significantly in the concentration of immunoglobulin A (IgA) (p < 0.01) and the concentration of tumor necrosis factor-α (TNF-α) (p < 0.05) throughout the late pregnancy period. Overall, adding enrichment items to confinement stalls can alleviate the chronic stress and the stereotypic behavior of sows, suggesting their potential to reduce welfare compromise.

The Feeding Behaviour Habits of Growing-Finishing Pigs and Its Effects on Growth Performance and Carcass Quality: A Review

Based on the available data of feeding behaviour habits (FBHs), this work aimed to discuss which type of pig, according to its FBHs, performs better and is more efficient. As pigs grow, average daily feed intake, meal size, and feeding rate increase, whereas small variations or even decreases in time spent eating and daily feeder visits have been reported. Moreover, the sex, breed, space allowance, feeder design, feed form, diet composition, and environmental conditions modify FBHs. On the other hand, the literature indicates the existence of four types of pigs: pigs that eat their daily feed intake in many short meals (nibblers) or in few large meals (meal eaters) combined with eating fast (faster eaters) or slow (slow eaters). The available scientific literature about ad libitum fed pigs suggests that pigs eating faster with bigger meals eat more, gain more weight, and are fatter than pigs eating less, slower, and with smaller meals. However, the feeding rate and the meal size do not influence feed efficiency. In conclusion, studies comparing growing-finishing pigs with similar feed intake, but different feeding rate and meal size are needed to better understand the influence of FBHs on feed efficiency.

Evolution of welfare indicators of pigs housed in deep bedding systems during growing and finishing phases: assessment of good health principles and housing conditions

The aim of the study was to monitor the evolution of welfare indicators of pigs throughout growing and finishing phases housed in a deep bedding system by principles of good health and housing. In all, 16,500 animals, distributed in 15 facilities, were evaluated over a 4-month period. Three assessments were carried out in each facility by a single evaluator, according to the following time distribution: phase one (75 to 85 days old), phase two (86 to 161 days old), and phase three (162 to 180 days old). Only the parameters related to good health and good housing were considered. Data were analyzed by logistic regression for longitudinal data. Poisson distribution was used on the coughing and sneezing data, with subsequent chi-square analysis. There were no cases of poor body condition, shivering, panting, huddling, tail biting, pumping, twisted snout, rectal prolapse, lameness, and skin conditions. The final evaluations were associated with greater chances of hernia and bursitis, with greater prevalence in males than in females. The prevalence of wound and manure on the body parameters was influenced by the interaction of the evaluation and animal category. The incidence of coughing and the number of animals presenting this symptom gradually increased, becoming considerably higher in the final stage of evaluation. Health-related problems change throughout the production cycle. The evaluation of a broad and reliable view on animal welfare allows for the most appropriate management of production systems using deep bedding.

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.

Tail-Biting in Pigs: A Scoping Review

Tail-biting is globally recognized as a welfare concern for commercial swine production. Substantial research has been undertaken to identify risk factors and intervention methods to decrease and understand this vice. Tail-biting appears to be multifactorial and has proven difficult to predict and control. The primary objective of the scoping review was to identify and chart all available literature on the risk factors and interventions associated with tail-biting in pigs. A secondary objective was to identify gaps in the literature and identify the relevance for a systematic review. An online literature search of four databases, encompassing English, peer-reviewed and grey literature published from 1 January 1970 to 31 May 2019, was conducted. Relevance screening and charting of included articles were performed by two independent reviewers. A total of 465 citations were returned from the search strategy. Full-text screening was conducted on 118 articles, with 18 being excluded in the final stage. Interventions, possible risk factors, as well as successful and unsuccessful outcomes were important components of the scoping review. The risk factors and interventions pertaining to tail-biting were inconsistent, demonstrating the difficulty of inducing tail-biting in an experimental environment and the need for standardizing terms related to the behavior.

Effects of stocking density on growth performance, blood parameters and immunity of growing pigs

This study was conducted to evaluate the effects of different stocking densities on growth performance, blood parameters, intestinal morphology and intestinal immunity of growing pigs. A total of 288 male pigs (44.35 ± 0.50 kg) were randomly assigned to groups with stocking densities of 2.46, 1.23 and 0.82 m²/pig for a month. The results showed that there was no significant difference on growth performance among groups. Pigs in the stocking density of 0.82 m²/pig had the lowest backfat thickness and spleen weight index among groups (P < 0.05). With increasing stocking density, the serum concentrations of blood urea nitrogen (BUN), transglutaminase (TGG), alkaline phosphatase (AKP) and immunoglobulin A (IgA) were increased, and albumin (ALB), albumin-to-globulin ratio (ALB:GLO), insulin-like growth factor-1 (IGF-1) and immunoglobulin (IgM) were decreased (P < 0.05), and cortisol tended to increase and glucose tended to decrease (0.05 < P < 0.1). Compared with the stocking density of 2.46 m²/pig, the ileal villus height and jejunal villus width decreased in stocking densities of 1.23 and 0.82 m²/pig (P < 0.05). The duodenal villus height and ileal villus width in the stocking density of 0.82 m²/pig were the lowest among 3 groups (P < 0.05). The content of immunoglobulin A in duodenum, jejunum and ileum mucosa increased along with increasing density (P < 0.05). The contents of interleukin (IL)-2 in the spleen or liver and IL-10 in the spleen were higher in the stocking density of 0.82 m²/pig than in other 2 groups. These results showed that stocking density could affect the metabolism, intestinal morphology, and immunity of growing pigs and 1.23 m²/pig may be the suitable stocking density for the growing pigs in the present study.

MicroRNAs as Biomarkers for Animal Health and Welfare in Livestock

MicroRNAs (miRNAs) are small and highly conserved non-coding RNA molecules that orchestrate a wide range of biological processes through the post-transcriptional regulation of gene expression. An intriguing aspect in identifying these molecules as biomarkers is derived from their role in cell-to-cell communication, their active secretion from cells into the extracellular environment, their high stability in body fluids, and their ease of collection. All these features confer on miRNAs the potential to become a non-invasive tool to score animal welfare. There is growing interest in the importance of miRNAs as biomarkers for assessing the welfare of livestock during metabolic, environmental, and management stress, particularly in ruminants, pigs, and poultry. This review provides an overview of the current knowledge regarding the potential use of tissue and/or circulating miRNAs as biomarkers for the assessment of the health and welfare status in these livestock species.

Health and welfare in organic livestock production systems—a systematic mapping of current knowledge

This review aimed to systematically map and summarize the status of animal health and welfare in organic production. The prevalence of diseases and behavioural effects in organic dairy cow, beef cattle, sheep, pig, laying hen and broiler chicken were discussed in the context of the organic values and current knowledge on animal health and welfare. In total 166 peer-reviewed scientific publications between 2008 and 2020 were included. No strong evidence for neither inferior nor distinctly higher animal welfare in organic compared with conventional production could be supported. The welfare status of organic livestock is in general good in relation to the OIE definition of animal health and welfare. However, organic systems are still facing several challenges related to animal health and the arising of goal conflicts due to management and practical implications. Greater possibilities to perform species-specific behaviours in organic production systems, however, indicate that the organic standards offer a good framework for high animal welfare management. For organic dairy farmers, the main health problems are similar to those of non-organic farms; especially mastitis and lameness need improvement. Parasites, together with mastitis and lamb mortality, are important welfare issues in organic sheep production. Piglet mortality, leg problems, parasite load and increasing respiratory problems are of major relevance in organic pig production. For organic laying hens, major health challenges relate to feather pecking and cannibalism, parasites and possibilities to express species-specific behaviours. For organic broilers, dermatitis of footpads, hocks and breast are reported as main health issues.

Time-Budget of Horses Reared for Meat Production: Influence of Stocking Density on Behavioural Activities and Subsequent Welfare

Simple Summary

Horses reared for meat production are kept in group pens at high stocking densities. Due to the lack of scientific knowledge concerning the welfare of horses reared in this way, the aim of the present work was to assess whether their behaviours were affected by stocking density. The time-budget of the horses was also studied to evaluate if and how it differed compared with that of wild-living horses. We found that the expression of locomotion, playing, and self-grooming increased as the space allowance per horse within the group pens increased, indicating the potential to use these behaviours as indicators of positive welfare. Moreover, an altered time-budget was identified, implicating the condition of compromised welfare in these animals. Standing was the main expressed behavioural activity. A higher than usual amount of time was spent in a lying position, and a lower than usual amount of time was dedicated to feeding and locomotion. This study was the first to assess the behaviour of horses reared for meat production. The results show that more attention needs to be directed at the housing and management conditions under which horses reared for meat production are kept in in order to improve their welfare.

Abstract

Horses reared for meat production can be kept in intensive breeding farms where they are housed in group pens at high stocking densities. The present study aimed to evaluate whether the expressed behaviours correlated with stocking density, and to compare their time-budget with that of wild-living horses. An ethogram of 13 mutually exclusive behavioural activities was developed. Behavioural observations were performed over a 72 h period on group pens selected on the basis of stocking density and the homogeneity of breed, age, height at the withers, and time since arriving at the farm. Scan sampling (n = 96 scans/horse/day) was used on 22 horses. The mean frequency (%) ± standard deviation (±SD) for each behavioural activity was calculated to obtain the time-budget. The associations between time-budget and stocking density were evaluated using a bivariate analysis. The relationships were analysed by Pearson’s correlation coefficient (r). Our results show that locomotion, playing, and self-grooming positively correlated with a reduction in stocking density, indicating the potential to use these behaviours as positive welfare indicators for young horses kept in group pens. The data also revealed an unusual time-budget, where the main behavioural activity expressed was standing (30.56% ± 6.56%), followed by feeding (30.55% ± 3.59%), lying (27.33% ± 2.05%), and locomotion (4.07% ± 1.06%).

A Review of the Effects of Non-Straw Enrichment on Tail Biting in Pigs

Simple Summary

Tail biting, a damaging behaviour that one pig directs at another, causes pain, wounding and health problems. It reduces both pig welfare and market value. Enrichment can reduce tail biting substantially. Many pig producers are reluctant to use straw as enrichment, but many non-straw alternatives exist. We aimed to evaluate their ability to reduce tail biting based on studies on the effects of enrichment on tail damage and manipulation of other pigs, and on the duration of interaction with enrichment. Additionally, we reviewed how pigs interact with different enrichments (e.g., by rooting or chewing it). This was done to clarify which type of enrichment could satisfy which behavioural motivation (that may lead to tail biting if not satisfied). However, very little information on separate enrichment-directed behaviours was uncovered. Several effective types of non-straw enrichment were identified, but these correspond poorly with the types of enrichment commonly applied on commercial farms. More detailed observations of how pigs interact with different enrichments, other pigs, and their environment would improve our understanding of how to combine enrichments to minimize tail biting. This is essential because although single non-straw enrichments can reduce tail biting significantly, the remaining levels of damage can still be high.

Abstract

Tail biting remains a common problem in pig production. As producers are reluctant to use straw to reduce this behaviour, we review studies on the effectiveness of other types of enrichment. Roughage, hessian sacks, compost, fresh wood, space dividers, rope, and providing new objects regularly can significantly reduce tail damage. These results should be interpreted with some caution, as often only one study per enrichment could be identified. No evidence was found that commonly applied enrichment objects (processed wood, plastic or metal) reduce tail biting significantly unless exchanged regularly, even though multiple studies per type of enrichment were identified. Many studies evaluated the duration of enrichment use, but few evaluated the manner of use. This hampers identification of combinations of enrichment that will satisfy the pig’s motivation to eat/smell, bite, root and change enrichments, which is suggested to reduce tail biting. New objects designed to satisfy specific motivations were shown to receive high levels of interaction, but their effectiveness at reducing tail damage remains unknown. More in-depth study of how pigs interact with non-straw enrichment, which motivations this satisfies and how this affects behaviour towards conspecifics, is necessary to optimize enrichment strategies. Optimization is necessary because ceasing tail docking in a way that improves pig welfare requires more effective enrichments than those described in this review, or alternatively, better control over other factors influencing tail biting.

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.

Effects of Enrichment Type, Presentation and Social Status on Enrichment Use and Behaviour of Sows with Electronic Sow Feeding

The goal of this study was to identify practical enrichments for sows in partially or fully slatted pen systems. Four treatments were applied: (1) Constant: constant provision of wood on chain; (2) Rotate: rotation of rope, straw and wood enrichments; (3) Stimulus: rotation of enrichments (as in Rotate) with an associative stimulus (bell or whistle); and (4) Control: no enrichment, with each treatment lasting 12 days. Six groups of 20 ± 2 sows were studied from weeks 6 to 14 of gestation in pens with one electronic sow feeder. Each group received all treatments in random order. Six focal animals (3 dominant and 3 subordinate) were selected per pen using a feed competition test. Digital photos were collected at 10 min intervals for 8 h (between 8 a.m. and 4 p.m.) on 4 days/treatment (d 1, 8, 10 and 12) to record interactions with enrichment. Skin lesions were assessed on days 1 and 12, and saliva cortisol samples collected in weeks 6, 10 and 14 of gestation on focal pigs. Sows spent more time in contact with enrichments in Rotate and Stimulus treatments than Constant. Enrichment treatments did not influence lesion scores. Subordinate sows spent more time standing and near enrichments than dominants. Subordinate sows also received more skin lesions and had higher salivary cortisol concentrations than dominants. These results indicate that access to enrichment is valued by sows but can result in greater aggression directed towards subordinates.

Effect of Different Environment Enrichments on Behaviour and Social Interactions in Growing Pigs

Simple Summary

Pigs reared under intensive conditions are subjected to environmental stresses such as being unable to express some natural behaviours, like socialisation, exploring and rooting. For this reason, EU legislation requires farmers to employ suitable environmental enrichments in the pens. This study aimed at evaluating how different environmental enrichment tools (wooden logs either hanging or laying and hanging metal chains in pens) affected the behaviour of growing pigs. The results show a reduction in the incidence of aggressive/damaging interactions between animals in the pen where hanging wooden logs were placed. No significant effect on non-aggressive behaviours was noted in any of the investigated conditions.

Abstract

(1) Background: Pigs are active animals that require a suitable environment to be able to express their exploratory behaviour. The aim of the present study was to compare the effects of different environmental enrichments on the behaviour, social interactions, salivary cortisol concentration and body weight of pigs during the growing phase. (2) Methods: The investigation involved 75 pigs divided into three groups. The environmental enrichments were arranged as follows: Hanging metal chains for the control group; hanging metal chains and hanging logs for the second group; hanging metal chains and logs laying on the floor for the third group. Each group was video recorded twice a week for six weeks. The scan sampling technique was used. Salivary cortisol and live body weight were also recorded regularly. Parametric (ANOVA) and non-parametric statistics were used to analyse the data. (3) Results: Hanging logs were found to be more effective than logs laying on the floor at reducing aggression within the group tested, resulting in a more comfortable environment. Salivary cortisol concentration and growth did not show significant differences between the three groups. (4) Conclusions: The use of hanging logs affected some interactive patterns that resulted in decreasing the aggressive episodes of pigs, thereby providing a more comfortable environment.

Effects of increased space allowance on animal welfare, meat and ham quality of heavy pigs slaughtered at 160Kg

Sixty barrows (Body Weight–BW- range: 23.9–160 kg) were allotted to two experimental groups (6 pens of 5 pigs each): the control group was kept at a space allowance of 1m²/head; the second group was kept at 1.3m²/head. Behaviour, growth parameters, carcass and meat quality were assessed, as well as fat and cured ham quality. Results showed that pigs raised at 1.3m²/head spent more time laying (particularly in lateral recumbency, P<0.01 and P<0.001, respectively) compared to pigs kept at lower space allowance. They also reduced the aimless exploration of the slatted pen floor (P<0.001) and increased overall expression of other, mainly active, behaviors (e.g., drinking, walking and standing, P<0.01). Pigs raised at 1.3m^2/head showed higher final BW (P = 0.02), more favourable Average Daily Gain (ADG) and gain-to-Feed ratio (G:F) both during the last period of the trial (P<0.05 for both parameters) and over the entire trial (P = 0.01 for both parameters). No significant difference was observed between groups for carcass traits and the main meat quality attributes. Subcutaneous fat from green hams had higher α-linolenic acid content (P<0.01) in the group reared at greater space allowance. Green hams from this group lost less weight at trimming (P<0.01) and the resulting cured hams received better sensory evaluations (P<0.05). No difference was observed in fatty acid composition and unsaturation levels of the subcutaneous fat from cured hams. Our data suggest that heavy pigs intended for Parma ham would benefit from the adoption of higher individual floor space allowances, both in terms of animal welfare (increased possibility to rest) and of productive parameters, without having any detrimental effect on the suitability of the thighs for dry-curing or on the quality of the final product.

Meat quality of pork loins from Hereford×Berkshire female and intact male pigs reared in an alternative production system

Objective

The objective of the present study was to investigate pork quality from Hereford× Berkshire female and intact male pigs reared outdoors in an alternative production system.

Methods

Berkshire purebred sows were artificially inseminated, once in the fall and again in the spring of the following year, with semen from Hereford boars and managed free of antibiotics in an outdoor hoop structure until the last month of pregnancy, after which they were moved to a pasture-based unit of 0.8 hectares with individual lots with a farrowing hut, shade, and water ad libitum. Piglets were weaned at 4 weeks of age and housed in a deep-bedded hoop structure, grouped by sex. Animals were harvested at market weight of 125 kg, approximately 200 days of age. Hot carcass weight was collected at the time of the harvest. After 24 hours of refrigeration, carcass characteristics were measured. Longissimus dorsi samples collected from the right side loin. Loins were cut into 2.54-cm thick chops and were used to measure marbling score, color score, drip loss, and ultimate pH. Sensory panel tests were conducted as well at North Carolina State University. For pork characteristics and sensory panel data, trial and sex were included in the statistical model as fixed effects. Hot carcass weight was included in the model as a covariate for backfat thickness.

Results

Neither the subjective nor the objective color scores displayed any differences between the boars and the gilts. No difference was found for pH and marbling score between trials or sexes. Gilts had a thicker backfat measurement at the last lumbar and a narrower longissimus muscle area measurement when compared to the boars. The only difference in the sensory characteristics was found between the trials for texture and moisture scores.

Conclusion

Consumers were not able to detect boar taint under the condition of this study, which is that the intact males were reared outdoors. Additional trials would be necessary; however, based on the results of the present study, outdoor rearing can be suggested as a solution to the issue of boar taint.

Effect of Artificial Piglet Suckling Sounds on Behavior and Performance of Piglets and Adrenal Responses of Sows

Operation of the farrowing house is essential to the productivity of a swine farm, requiring not only good management but also knowledge of the behavior of sows and piglets. Stress can negatively affect production in farm animals and could be a factor in production indexes. The objective of this study was to investigate the effect of artificial sucking sounds on the behavior of piglets and fecal glucocorticoid (FGM) concentrations of sows. A total of 30 sows were divided into two groups: a treatment group (15 sows) was exposed to artificial sucking sounds and a control group (15 sows) was not. Both groups received the same management; the two open-house system locations were separated by a distance of about 270 meters. The study had three key objectives: to compare farrowing indexes and to observe the sucking behavior of piglets using CCTV cameras. Fecal samples were collected daily for 21 days from the period after parturition to weaning to assess adrenal activity. The treatment group had a significantly higher average number of times piglets came to a sow's udder, and sows had a shorter onset time for the first piglet to come to the sow's udder than the control group (both P<0.05). The patterns and levels of FGM between the two groups were not different (both P<0.05), but the treatment group had better farrowing indexes than the control group (P>0.05), particularly for litter weight gain and percent preweaning mortality. In addition, the weaning to first service interval of the treatment group was shorter than the control group (P<0.05). This indicates that the artificial suckling sound probably has no adverse effect on adrenal responses of pig; however, it improves production indexes of postparturition sows.

Transcriptomic response to parasite infection in Nile tilapia (Oreochromis niloticus) depends on rearing density

Background

Captive animal populations, be it for food production or conservation programmes, are often maintained at densities far beyond those in natural environments, which can have profound effects on behaviour, immune and stress levels, and ultimately welfare. How such alterations impact transcriptional responses to pathogen infection is a ‘different kettle of fish’ and remains poorly understood. Here, we assessed survival and gene expression profiles of infected fish reared at two different densities to elucidate potential functional genomic mechanisms for density-related differences in disease susceptibility.

Results

Utilising a whole-transcriptome sequencing (RNAseq) approach, we demonstrate that rearing density in tilapia (Oreochromis niloticus) significantly impacts susceptibility to the oomycete Saprolegnia parasitica, via altered transcriptional infection responses. Tilapia held at low densities have increased expression of genes related to stress, likely due to increased aggressive interactions. When challenged with Saprolegnia, low-density fish exhibit altered expression of inflammatory gene responses and enhanced levels of adaptive immune gene suppression compared to fish reared at higher density, resulting in significantly increased mortality rates. In addition, Saprolegnia infection substantially perturbs expression of circadian clock genes, with fish reared at low-density having higher levels of molecular clock dysregulation.

Conclusions

Our results reveal the wide-scale impact of stocking density on transcriptional responses to infection and highlight the need to incorporate circadian biology into our understanding of disease dynamics in managed animals.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5098-7) contains supplementary material, which is available to authorized users.

Does the location of enrichment material affect behavior and dirtiness in growing female pigs?

The objective of this study was to investigate if female growing pigs spend similar amounts of time exploring a wooden stick as they do exploring enrichment material regardless of its proximity to the feeder. Forty-eight pigs aged 18 to 26 weeks allocated to 16 pens with three pigs per pen were studied. Fifty percent of the pens had a wooden stick beside the feeder, and the rest had a similar stick opposite to the feeder. Two observers assessed the pigs by means of scan and focal sampling. The pigs spent more time (p < .0001) exploring the wood during the first week than during the rest of the study (10.9% vs 3.6%). The pigs with the wood close to the feeder spent less (p = .0001) time resting (29.9%) and more (p < .0001) time exploring (6.3%) the wood than did pigs with the wood opposite to the feeder (32.4% and 2.5%, respectively). In conclusion, a wooden stick placed close to the feeder was associated with more exploratory behaviorcompared with a similar stick placed opposite to the feeder.

Connecting Different Data Sources to Assess the Interconnections between Biosecurity, Health, Welfare, and Performance in Commercial Pig Farms in Great Britain

This study aimed to provide an overview of the interconnections between biosecurity, health, welfare, and performance in commercial pig farms in Great Britain. We collected on-farm data about the level of biosecurity and animal performance in 40 fattening pig farms and 28 breeding pig farms between 2015 and 2016. We identified interconnections between these data, slaughterhouse health indicators, and welfare indicator records in fattening pig farms. After achieving the connections between databases, a secondary data analysis was performed to assess the interconnections between biosecurity, health, welfare, and performance using correlation analysis, principal component analysis, and hierarchical clustering. Although we could connect the different data sources the final sample size was limited, suggesting room for improvement in database connection to conduct secondary data analyses. The farm biosecurity scores ranged from 40 to 90 out of 100, with internal biosecurity scores being lower than external biosecurity scores. Our analysis suggested several interconnections between health, welfare, and performance. The initial correlation analysis showed that the prevalence of lameness and severe tail lesions was associated with the prevalence of enzootic pneumonia-like lesions and pyaemia, and the prevalence of severe body marks was associated with several disease indicators, including peritonitis and milk spots (r > 0.3; P < 0.05). Higher average daily weight gain (ADG) was associated with lower prevalence of pleurisy (r > 0.3; P < 0.05), but no connection was identified between mortality and health indicators. A subsequent cluster analysis enabled identification of patterns which considered concurrently indicators of health, welfare, and performance. Farms from cluster 1 had lower biosecurity scores, lower ADG, and higher prevalence of several disease and welfare indicators. Farms from cluster 2 had higher biosecurity scores than cluster 1, but a higher prevalence of pigs requiring hospitalization and lameness which confirmed the correlation between biosecurity and the prevalence of pigs requiring hospitalization (r > 0.3; P < 0.05). Farms from cluster 3 had higher biosecurity, higher ADG, and lower prevalence for some disease and welfare indicators. The study suggests a smaller impact of biosecurity on issues such as mortality, prevalence of lameness, and pig requiring hospitalization. The correlations and the identified clusters suggested the importance of animal welfare for the pig industry.

Effect of enriched housing on levels of natural (auto-)antibodies in pigs co-infected with porcine reproductive and respiratory syndrome virus (PRRSV) and Actinobacillus pleuropneumoniae

Housing of pigs in barren, stimulus-poor housing conditions may influence their immune status, including antibody responses to (auto-)antigens, and thus affect immune protection, which will influence the onset and outcome of infection. In the present study, we investigated the effects of environmental enrichment versus barren housing on the level of natural (auto-)antibodies (NA(A)b) and their isotypes (IgM and IgG) binding keyhole limpet hemocyanin (KLH), myelin basic protein (MBP), and phosphorycholine conjugated to bovine serum albumin (PC-BSA) in pigs co-infected with porcine reproductive and respiratory syndrome virus (PRRSV) and Actinobacillus pleuropneumoniae (A. pleuropneumoniae). Pigs (n = 56) were housed in either barren or enriched pens from birth to 54 days of age. They were infected with PRRSV on 44 days of age, and with A. pleuropneumoniae 8 days later. Blood samples were taken on 7 different sampling days. Housing significantly affected the overall serum levels of NA(A)b binding KLH, MBP and PC-BSA, and before infection barren housed pigs had significantly higher levels of NA(A)b than enriched housed pigs, except for KLH-IgM and PC-BSA-IgG. Infection only affected the IgM, but not the IgG isotype. Moreover, changes in MBP-IgM and PC-BSA-IgM following infection were different for enriched and barren housed pigs. These results suggest that the effect of infection on NA(A)b is influenced by housing conditions and that NA(A)b, especially IgM may be affected by infection.

Which is the most preventive measure against tail damage in finisher pigs: tail docking, straw provision or lowered stocking density?

One challenge of intensive pig production is tail damage caused by tail biting, and farmers often decrease the prevalence of tail damage through tail docking. However, tail docking is not an optimal preventive measure against tail damage and thus, it would be preferable to replace it. The aim of the current study was to investigate the relative effect of three possible preventive measures against tail damage. The study included 112 pens with 1624 finisher pigs divided between four batches. Pens were randomly assigned to one level of each of three treatments: (1) tail-docked (n=60 pens) v. undocked (n=52 pens), (2) 150 g of straw provided per pig per day on the solid floor (n=56 pens) v. no straw provided (n=56 pens), (3) stocking density of 1.21 m2/pig (11 pig/pen; n=56 pens) v. 0.73 m2/pig (18 pigs/pen; n=56 pens). Tail damage was recorded three times per week throughout the finisher period by scoring the tail of each individual pig. A pen was recorded as a tail damage pen and no longer included in the study if at least one pig in a pen had a bleeding tail wound; thus, only the first incidence of tail damage on pen level was recorded. Data were analysed by a Cox regression for survival analysis assuming proportional hazards. Results are presented as hazards, and a higher hazard means that a pen has a higher risk of tail damage and of it happening earlier in the finisher period. Pens with undocked pigs had a 4.32-fold higher hazard of tail damage compared with pens with docked pigs (P<0.001). Pens with no straw provided had a 2.22-fold higher hazard of tail damage compared with pens with straw provided (P<0.01). No interactions was seen between the treatments, but the effect of tail docking was higher than the effect of straw provision (P<0.001). Stocking density did not have a significant effect on the hazard of tail damage (hazard rate ratios (HRR)=1.67; P=0.064). However, a combination of straw provision and lowered stocking density showed a similar hazard of tail damage as seen with only tail docking (HRR=1.58; P=0.39). In conclusion, tail docking and straw provision were preventive measures against tail damage, and tail docking reduced the risk more than straw provision. A combination of other preventive measures is necessary to reduce the risk of tail damage in undocked pigs to the same level as in docked pigs.

The "Real Welfare" scheme: Identification of risk and protective factors for welfare outcomes in commercial pig farms in the UK

From 2013-2016, animal-based measures were collected as part of the "Real Welfare" protocol adopted by the Red Tractor Pigs Assurance Scheme to assess the welfare in finisher pig herds in the UK. Trained veterinarians from 89 veterinary practices assessed 112,241 pens (hospital pens excluded) from 1928 farms using a multistage sampling protocol, and collected data about pig welfare, management and farm environment. Multivariable analyses were conducted for five main welfare outcomes: lameness, pigs requiring hospitalization, severe tail lesions, severe body marks and enrichment use ratio (number of active pigs interacting with the enrichment/total number of active pigs). Additionally, a multiple correspondence analysis (MCA) was conducted to analyse systematic patterns of variations of environmental characteristics and improve understanding of the connection between welfare outcomes and environment. The prevalence of the four welfare outcomes and the mean enrichment use ratio differed between pen types (P<0.05), with a higher mean prevalence of lame pigs (0.39%) but lower mean prevalence of pigs requiring hospitalization (0.07%), severe tail lesions (0.07%) and severe body marks (0.12%) in outdoor pens. In&outdoor pens had the highest mean prevalence of the measured outcomes (P<0.05). After adjusting for the farm, date and pen type, lameness, pigs requiring hospitalization and severe tail lesions were less prevalent in large pens (P<0.01), pens with substrates (P≤0.05) and pens fed with meal (P≤0.05), while enrichment use ratio was higher with substrates (P<0.001). Moreover, pigs requiring hospitalization and severe body marks were more prevalent in pens with powered ventilation (P<0.05). On the MCA graph, higher prevalences of lameness and pigs requiring hospitalization (>1, 5 and 10%) were located in the same direction as lower enrichment use ratio, liquid feed, trough feeding, floor feeding, restricted feed and in&outdoor pens. Results suggested that higher prevalences were not specifically connected to a particular system, but that all welfare outcomes were connected to several inappropriate features in the environment. This study highlights individual risk factors which can be considered to improve animal welfare, but also indicates the need to consider the environment as a whole because of potential factor combinations and confounds. Understanding of these requires a large scale database, which can be drawn from assessments carried out as part of farm assurance and support evidence-based advice and future formulation of standards for good practice.

A two-level pen for fattening pigs: Effects on behavior, performance, and postslaughter measurements

Concurrent with a tendency toward higher slaughter weights of fattening pigs, minimum requirements for space allowance are increasing. Allowing pigs more space in existing standard pens, however, leads to a decrease in the number of pigs per pen, which jeopardizes the economic viability of the pig farm. A possible solution includes creating a two-level pen by constructing a second level in an existing pen, to enable an increase in space allowance per pig with the same number of pigs. We investigated the effect of such a pen on the behavior, performance, and postslaughter results of fattening pigs during the entire fattening period (30 to 110 kg). A total of 444 pigs were distributed over standard control pens (0.74 m/pig) and two-level pens (0.99 m/pig). Feed was provided only in a trough at the ground level of the pen. The results show that the increased space allowance and choice of levels in two-level pens influenced the pigs' behavior in a positive way, as they performed less manipulation of pen mates ( < 0.0001). Moreover, pigs lay down more ( = 0.0007) and showed less head knocking ( = 0.005) in two-level pens, suggesting that they were calmer. In line with the behavioral results, pigs in two-level pens had fewer lesions on tails ( = 0.006), ears ( = 0.008), and shoulders ( = 0.01). Growth performance was not affected ( > 0.05), but postslaughter measurements revealed fewer livers with white spots in pigs from two-level pens. This result might be related to lower disease pressure in pens with lower stocking densities. In conclusion, a two-level pen seemed to have positive effects on the behavior of pigs (in terms of pen mate manipulation) and the increase in space allowance seemed to make the pigs calmer. The use of the second level by heavier pigs should, however, be further studied to investigate whether this extra space could be fully counted for the minimal space requirements.

CONDITIONING METHODS FOR ANIMALS IN AGRICULTURE: A REVIEW

Abstract This article briefly describes different conditioning techniques used to help understand learning in farm livestock and economically important animals. A basic overview of conditioning is included along with the importance of different conditioning methods, associative and non-associative learning, and how these principles apply to chickens, horses, cows, goats, pigs, and sheep. Additional information on learning theory specific for each animal is also provided.

Frequency of tail lesions and risk factors for tail biting in heavy pig production from weaning to 170 kg live weight

Tail biting lesions have a negative effect on both the welfare of pigs and on the revenue of the pig farm. Due to the multifactorial nature of this abnormal behaviour and its sporadic onset, an epidemiological approach was adopted to identify the management and housing factors influencing the occurrence of tail biting and the frequency of bitten pigs in the weaning and fattening phases up to 170 kg live weight in heavy pig production. Data were collected from a sample of 67 commercial pig farms via an on-farm visit and a questionnaire to the farmer. Data collected included general farm information, hygiene and herd health, prevention, management, climate control, feeding and production traits. In the weaning phase, the occurrence of tail biting was increased by a factor of 16.64 for tipped vs. short-docked tails, by a factor of 68.09 when the observer detected poor air quality, and by a factor of 14.44 when the feeding time was variable. In fattening pigs, a high stocking density increased the risk of tail biting by a factor of 18.00. The frequency of lesions in weaners was greater in pigs with tipped tails (0.29 vs. 0.03%; P = 0.034), whereas in fatteners the frequency of lesions was greater when drinkers were not present in the lying area (0.71 vs. 0.05%; P = 0.009) and when air turnover was not detected in the barn (0.70 vs. 0.07%; P = 0.005). There was also a trend for increased tail biting when the stocking density was high (1.06 vs. 0.33%; P = 0.057). Many of the risk factors that emerged for heavy pigs in the present study could be easily managed to reduce the risk of tail biting and the frequency of tail lesions through the systematic evaluation and control of stocking density, climate, and feed and water management.