Special Issue "Environmental Enrichment of Pigs"

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Pigs".

Deadline for manuscript submissions: closed (28 February 2019).

Special Issue Editor

Dr. Emma Fàbrega i Romans
E-Mail Website
Guest Editor
IRTA, Veïnat de Sies s/n, 17121 Monells, Spain
Interests: behavior; animal welfare; stress; pig; farming

Special Issue Information

Dear Colleagues,

The limitation to fulfil ethological and physiological needs can negatively affect animal welfare and cause the development of abnormal behaviour. Pigs have a strong motivation to perform exploratory and foraging behaviour from a very young age, even if they are provided with enough feed to satisfy their dietary needs. Tail-biting is a redirected behaviour said to be a response to insufficient stimulation and frustration in association with other negative environmental and management factors. Although the exact triggering mechanisms remain unclear, tail-biting has a multifactorial origin, and the scientific evidence has identified a wide range of environmental, dietary, and husbandry risk factors. The lack of adequate enrichment material appears to be an initial risk factor that may trigger stress and has been considered a major cause for the most common type of tail biting, the so-called two-stage tail biting, which starts with gentle manipulation of another pig’s tail and proceeds to more intensive manipulation with the teeth, causing bleeding and damage. Therefore, tail biting becomes not only an important welfare concern, but it also has serious economic consequences for pig producers, because it lowers weight gains and increases susceptibility to secondary infections, antibiotic use, and carcass condemnations. Up to now, tail docking is the most widely preventive measure against tail biting adopted by farmers, although it is considered to cause acute pain, and it does not totally prevent tail biting, since it does not address the underlying causes. The EU legislation of pig welfare does not allow routine tail docking unless other measures such as environmental and management conditions have been tackled. Moreover, EU legislation specifically states that “pigs must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities”. However, provision of adequate enrichment materials is not easy in modern intensive production systems, since a lot of them use either totally or partially slatted floors. There is a certain mismatch between those materials that are meaningful for pigs to fulfil their behavioural needs (i.e., straw-type materials) and those that do not cause any blockage to the slurry systems (i.e., object-type materials). Therefore, an important challenge for researchers is to deliver data and practical solutions on enrichment materials with attributes that satisfy pigs’ needs, that is, being manipulable, investigable, safe, edible, and chewable, but suitable to be implemented in intensive production systems. The aim of this Special Issue is to collate recent research on “enrichment materials for pigs”, tailored to different climatic conditions and pig production systems.

We invite original research papers that address new insights on enrichment materials for pigs or on how to implement those materials on commercial farms. Topics of special interest include: effects of enrichment material on welfare, pig handling responses, and productivity; effectiveness of enrichment materials to avoid tail biting; adequate enrichment materials for all production stages; carry-over effects of enrichment materials provided during the early development stage; a cost-benefit analysis of providing enrichment materials; and overcoming practical barriers to implement enrichment materials. Additional topics may include practical strategies to evaluate the effectiveness of enrichment materials on farms and strategies to communicate and increase farmers’ involvement in the use of enrichment materials as a mean to avoid tail docking.

Dr. Emma Fàbrega i Romans
Guest Editor

Manuscript Submission Information

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Keywords

  • enrichment material
  • pig
  • welfare
  • tail biting
  • tail docking
  • exploratory behaviour

Published Papers (12 papers)

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Editorial

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Open AccessEditorial
How Far Are We from Providing Pigs Appropriate Environmental Enrichment?
Animals 2019, 9(10), 721; https://doi.org/10.3390/ani9100721 - 24 Sep 2019
Abstract
Limitations to the fulfilment of ethological and physiological needs can cause countless negative effects on animal welfare and lead to the development of abnormal behaviours [...] Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)

Research

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Open AccessArticle
Are Tail and Ear Movements Indicators of Emotions in Tail-Docked Pigs in Response to Environmental Enrichment?
Animals 2019, 9(7), 449; https://doi.org/10.3390/ani9070449 - 16 Jul 2019
Abstract
The inclusion of emotional indicators in farm monitoring methods can improve welfare assessments. Studies in controlled conditions have suggested that increased tail movement is an indicator of positive emotions in pigs, while others have proposed that increased ear movements are linked to negative [...] Read more.
The inclusion of emotional indicators in farm monitoring methods can improve welfare assessments. Studies in controlled conditions have suggested that increased tail movement is an indicator of positive emotions in pigs, while others have proposed that increased ear movements are linked to negative emotions. This study aimed to investigate these indicators in pig farm conditions to analyze their validity and the effect of enrichment on welfare. Thirty-six pigs received one of the following enrichment materials: straw in a rack, wooden logs, or chains. Behavioral observations were performed by focal sampling. The results showed that tail movement duration was significantly higher when pigs exhibited “high use” (three or more pigs in a pen interacting with the enrichment) than when they exhibited “low use” (fewer than three) of enrichment (p = 0.04). A positive correlation was found between tail movement frequency and duration (r = 0.88; p = 0.02). The increase in tail movement could be considered an indicator of positive emotions in pigs when measured with other categories of indicators. Regarding ear movements, no significant difference was found. Future studies should further investigate these indicators thoroughly, as the results could be useful for improving the assessment of emotions in pigs. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
Effects of Enrichment Type, Presentation and Social Status on Enrichment Use and Behaviour of Sows with Electronic Sow Feeding
Animals 2019, 9(6), 369; https://doi.org/10.3390/ani9060369 - 18 Jun 2019
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
The Effect of Straw, Rope, and Bite-Rite Treatment in Weaner Pens with a Tail Biting Outbreak
Animals 2019, 9(6), 365; https://doi.org/10.3390/ani9060365 - 17 Jun 2019
Cited by 2
Abstract
Tail biting in pigs is an injurious behaviour that spreads rapidly in a group. We investigated three different treatments to stop ongoing tail biting outbreaks in 65 pens of 6–30 kg undocked pigs (30 pigs per pen; SD = 2): (1) straw (7 [...] Read more.
Tail biting in pigs is an injurious behaviour that spreads rapidly in a group. We investigated three different treatments to stop ongoing tail biting outbreaks in 65 pens of 6–30 kg undocked pigs (30 pigs per pen; SD = 2): (1) straw (7 g/pig/day on the floor), (2) rope, and (3) Bite-Rite (a hanging plastic device with chewable rods). Pigs were tail scored three times weekly, until an outbreak occurred (four pigs with a tail wound; day 0) and subsequently once weekly. After an outbreak had occurred, a subsequent escalation in tail damage was defined if four pigs with a fresh tail wound were identified or if a biter had to be removed. Straw prevented an escalation better (75%) than Bite-Rite (35%; p < 0.05), and rope was intermediate (65%). Upon introduction of treatments (day 0), pigs interacted less with tails than before (day −1; p < 0.05). Behavioural observations showed that pigs engaged more with rope than Bite-Rite (p < 0.05). Bite-Rite pigs (but not straw or rope) increased their interaction with tails between day 0 and day 7 (p < 0.05). Straw was the most effective treatment. However, further investigations may identify materials or allocation strategies which are more effective still. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
The Effects of Environmental Enrichment on the Physiology, Behaviour, Productivity and Meat Quality of Pigs Raised in a Hot Climate
Animals 2019, 9(5), 235; https://doi.org/10.3390/ani9050235 - 13 May 2019
Cited by 1
Abstract
Some positive effects regarding the use of enrichment material on the stimulation of pig exploration and a reduction in redirected behaviour was reported. This study aims to evaluate the effects of four enrichment materials on the behaviour, physiology/health, performance and carcass and meat [...] Read more.
Some positive effects regarding the use of enrichment material on the stimulation of pig exploration and a reduction in redirected behaviour was reported. This study aims to evaluate the effects of four enrichment materials on the behaviour, physiology/health, performance and carcass and meat quality in pigs kept in Spanish production conditions. Ninety-six male pigs (six pigs/pen) ranging from 70 to 170 days old were used. Chains were used for the control group (CH), and wooden logs (W), straw in a rack (S) or paper (P) were also used. The pigs were subjected to two pre-slaughter treatments: 0 or 12 h of fasting. Their behaviour was observed for 12 weeks using scan and focal sampling. Samples of the Neutrophil: Lymphocyte (N:L) ratio and lactate were obtained from the pigs at 66 and 170 days old. Saliva samples for Chromogranin-A (CgA) were obtained at 67, 128, 164 and 170 days old. The weight, skin lesions and feed intake of the pigs were recorded. S triggered more exploratory behaviour than W and CH (P < 0.001). Skin lesions and redirected behaviour were lower for pigs with S (P < 0.01 and P < 0.05, respectively). The pigs offered S presented lower CgA after no fasting than pigs with P or CH (P = 0.055). Lactate was higher in pigs with W and CH treatments, regardless of fasting (P < 0.05). The N:L ratio increased over time (P < 0.05). No other significant effects were found. Overall, straw in a rack was the enrichment material that enhanced pig inherent behaviour. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
The Use of Garlic Oil for Olfactory Enrichment Increases the Use of Ropes in Weaned Pigs
Animals 2019, 9(4), 148; https://doi.org/10.3390/ani9040148 - 05 Apr 2019
Abstract
Pig producers are required to provide environmental enrichment to provide pigs the opportunity to perform investigative and manipulative behaviours (EU directive 2001/93/EC). Preventing enrichment from losing its novelty and decreasing the rate at which animals become habituated is important to maintain use of [...] Read more.
Pig producers are required to provide environmental enrichment to provide pigs the opportunity to perform investigative and manipulative behaviours (EU directive 2001/93/EC). Preventing enrichment from losing its novelty and decreasing the rate at which animals become habituated is important to maintain use of enrichment over time. A comparative study was formulated to identify whether weaner pigs housed in a semi-barren environment displayed a preference for olfactory enrichment compared to non-scented enrichment. Pigs (n = 146) were selected at 28 days old from two different batches (n = 76 and n = 70) and divided into pens. All pigs were given a control and a treatment (garlic scented) rope. Behavioural observations and rope interactions were assessed through direct observation. Throughout the entire study, the length of interaction with the garlic device was significantly higher (p < 0.02), indicating that there was a preference for olfactory enrichment compared to an odourless device. There was no significant occurrence of tail, ear, or flank biting in both batches. Weaner pigs showed a preference towards olfactory enrichment. Although habituation began to occur, this effect was mitigated by re-spraying the ropes, which resulted in increased interactions. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
Rearing Undocked Pigs on Fully Slatted Floors Using Multiple Types and Variations of Enrichment
Animals 2019, 9(4), 139; https://doi.org/10.3390/ani9040139 - 02 Apr 2019
Cited by 1
Abstract
In fully slatted systems, tail biting is difficult to manage when pigs’ tails are not docked because loose enrichment material can obstruct slurry systems. This pilot study sought to determine: a) whether intact-tailed pigs can be reared with a manageable level of tail [...] Read more.
In fully slatted systems, tail biting is difficult to manage when pigs’ tails are not docked because loose enrichment material can obstruct slurry systems. This pilot study sought to determine: a) whether intact-tailed pigs can be reared with a manageable level of tail biting by using multiple slat-compatible enrichment; b) whether a variation of enrichment has an effect; and c) whether pigs show a preference in enrichment use. Ninety-six undocked pigs were given the same enrichment items from one week after birth until weaning. At weaning, four different combinations of 8 enrichment items were utilized based on predefined characteristics. These were randomly assigned to 8 pens (n = 12 pigs/pen). Four pens had the same combination (SAME) from assignment and four pens switched combinations every two weeks (SWITCH). Individual lesion scores, interactions with the enrichment, and harmful behaviours were recorded. The average tail score during the experiment was low (0.93 ± 0.02). Only one pig in a SAME pen had a severely bitten tail (partly amputated). The overall level of interaction with enrichment did not decline over time. Pigs interacted with a rack of loose material most frequently (p < 0.001). The study showed promising results for rearing undocked pigs on fully slatted floors using slat-compatible enrichment. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
Effect of Different Environment Enrichments on Behaviour and Social Interactions in Growing Pigs
Animals 2019, 9(3), 101; https://doi.org/10.3390/ani9030101 - 19 Mar 2019
Cited by 1
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 [...] Read more.
(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. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
Open AccessArticle
Growing Pigs’ Interest in Enrichment Objects with Different Characteristics and Cleanliness
Animals 2019, 9(3), 85; https://doi.org/10.3390/ani9030085 - 08 Mar 2019
Cited by 1
Abstract
Enrichment objects can be a practical way to provide rooting and chewing material to growing pigs, on which they can express species-specific behaviors. The challenge is to provide enrichment objects that will satisfy pigs’ behavioral needs, while being practical and low-cost for the [...] Read more.
Enrichment objects can be a practical way to provide rooting and chewing material to growing pigs, on which they can express species-specific behaviors. The challenge is to provide enrichment objects that will satisfy pigs’ behavioral needs, while being practical and low-cost for the producers. Two trials were conducted to evaluate the effects of object characteristics such as design, location, cleanliness or degree of wear, on pigs’ interest over time. The first trial compared seven objects, varying in their design and location, presented individually for five consecutive days to groups of 12 ± 3 (average ± SD) pigs, weighing 61 ± 9.2 kg. The pigs’ interest in the objects was evaluated based on the frequency, total duration and mean length of manipulation with the objects. All objects were manipulated at different levels depending on their characteristics. On average, the pigs interacted more frequently (p < 0.001) with a chewable object made of three polyurethane balls, spring-mounted and anchored to the floor, and spent more time manipulating a dried wood beam on the floor (p < 0.05), which was destructible and chewable, than suspended ropes, plastics and rubber objects, and a plastic ball on the floor. The second trial used two-choice preference tests to compare objects varying in their degree of cleanliness or wear, presented in pairs to growing pigs weighing 47 ± 7 kg and housed in groups of 14 ± 1. Two identical objects were placed simultaneously in a pen over 5 days, and only one of them was cleaned or replaced daily (treatment) while the duplicate was left untouched (control). The results showed no clear preference between control and treatment objects, indicating that short-term maintenance of the objects might be unnecessary. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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Open AccessArticle
Tail Posture as an Indicator of Tail Biting in Undocked Finishing Pigs
Animals 2019, 9(1), 18; https://doi.org/10.3390/ani9010018 - 08 Jan 2019
Abstract
Tail posture (i.e., hanging or curled) has been suggested to be an indicator of tail biting, and hanging tails predisposed to damage. The aim of this study was to investigate if tail posture was feasible as a tail damage indicator in a commercial [...] Read more.
Tail posture (i.e., hanging or curled) has been suggested to be an indicator of tail biting, and hanging tails predisposed to damage. The aim of this study was to investigate if tail posture was feasible as a tail damage indicator in a commercial setting. The study was carried out on one batch of 459 undocked finishing pigs (30–120 kg in weight). Weekly scoring of tail posture was combined with the scoring of tail lesions. Tail posture was observed at feeding to facilitate the usage of the method in commercial settings. A curly tail was observed in 94% of the observations. Pigs with tails scored with “wound” were 4.15 (p < 0.0001) times more likely to have hanging tails, and pigs scored with “inflamed wounds” were 14.24 (p < 0.0001) times more likely to have hanging tails, compared to pigs with nondamaged tails. Tail posture correctly classified tails with “wound” or “inflamed wound” 67.5% of the time, with 55.2% sensitivity and 79.7% specificity, respectively. The method of observing the tail position at feeding seems useful as a complement to normal inspection for detecting tail biting before tail wounds are visible to the caretaker. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)

Review

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Open AccessReview
Providing Effective Environmental Enrichment to Pigs: How Far Have We Come?
Animals 2019, 9(5), 254; https://doi.org/10.3390/ani9050254 - 21 May 2019
Cited by 5
Abstract
Science has defined the characteristics of effective environmental enrichment for pigs. We provide an overview of progress towards the provision of pig enrichment in the three largest global pork producing regions. In the USA, enrichment has not yet featured on the policy agenda, [...] Read more.
Science has defined the characteristics of effective environmental enrichment for pigs. We provide an overview of progress towards the provision of pig enrichment in the three largest global pork producing regions. In the USA, enrichment has not yet featured on the policy agenda, nor appeared on farms, except when required by certain farm assurance schemes. China has very limited legal animal welfare provisions and public awareness of animal welfare is very low. Food safety concerns severely restrict the use of substrates (as enrichment) on farms. Providing enrichment to pigs is a legal requirement in the EU. In practice, enrichment is not present, or simple (point-source) objects are provided which have no enduring value. Other common issues are the provision of non-effective or hazardous objects, inadequate presentation, location, quantity and size or inadequate maintenance of enrichment. Improvements can be made by applying principles from the field of experimental analysis of behaviour to evaluate the effectiveness of enrichment; providing welfare knowledge transfer, including training and advisory services; highlighting the economic benefits of effective enrichment and focusing on return on investment; increasing pressure from the financial sector; using novel drivers of change, such as public business benchmarking. The poor implementation of scientific knowledge on farms suggests that the pig industry has not fully embraced the benefits of effective enrichment and is still a long way off achieving an enriched pig population. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)

Other

Open AccessCommentary
Efforts to Ban the Routine Tail Docking of Pigs and to Give Pigs Enrichment Materials via EU Law: Where Do We Stand a Quarter of a Century on?
Animals 2019, 9(4), 132; https://doi.org/10.3390/ani9040132 - 29 Mar 2019
Cited by 5
Abstract
In its role as guardian of the Treaties, the European Commission must ensure that Member States enforce EU law within their territories. If adequate enforcement is found to be wanting, the Commission also has the power to take infringement procedures as a corrective [...] Read more.
In its role as guardian of the Treaties, the European Commission must ensure that Member States enforce EU law within their territories. If adequate enforcement is found to be wanting, the Commission also has the power to take infringement procedures as a corrective measure. The case of Directive 120/2008/EC on the protection of pigs is problematic, as only a few Member States are respecting the ban on routine tail docking, whilst not all pigs are given (adequate) enrichment materials. Twenty-five years after the first EU-wide legal ban on routine tail docking came into force, we are faced with an unprecedented situation that may lead to infringement procedures against more than 20 Member States. This paper describes the various steps that led to the development of the EU law designed specifically to safeguard the welfare of pigs. It lists the numerous efforts (research studies, study visits, recommendations, audits, reports, factsheets, action plans, etc.), undertaken by European decision makers to assist Member States in their efforts to better implement and enforce the relevant rules. Finally, the paper further analyses the current state of play and presents a reflection on possible future scenarios. Full article
(This article belongs to the Special Issue Environmental Enrichment of Pigs)
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