Tail Docking in Pigs: A Review on its Short- And Long-Term Consequences and Effectiveness in Preventing Tail Biting

Detecting tail biters by monitoring pig screams in weaning pigs

Early identification of tail biting and intervention are necessary to reduce tail lesions and their impact on animal health and welfare. Removal of biters has become an effective intervention strategy, but finding them can be difficult and time-consuming. The aim of this study was to investigate whether tail biting and, in particular, individual biters could be identified by detecting pig screams in audio recordings. The study included 288 undocked weaner pigs housed in six pens in two batches. Once a tail biter (n = 7) was identified by visual inspection in the stable and removed by the farm staff, the previous days of video and audio recordings were analyzed for pig screams (sudden increase in loudness with frequencies above 1 kHz) and tail biting events until no biting before the removal was observed anymore. In total, 2893 screams were detected in four pens where tail biting occurred. Of these screams, 52.9% were caused by tail biting in the observed pen, 25.6% originated from other pens, 8.8% were not assignable, and 12.7% occurred due to other reasons. In case of a tail biting event, screams were assigned individually to biter and victim pigs. Based on the audio analysis, biters were identified between one and nine days prior to their removal from the pen after visual inspection. Screams were detected earlier than the increase in hanging tails and could therefore be favored as an early warning indicator. Analyzing animal vocalization has potential for monitoring and early detection of tail biting events. In combination with individual marks and automatic analysis algorithms, biters could be identified and tail biting efficiently reduced. In this way, biters can be removed earlier to increase animal health and welfare.

Identifying areas of animal welfare concern in different production stages in Danish pig herds using the Danish Animal Welfare Index (DAWIN)

Animal welfare is of increasing public interest, and the pig industry in particular is subject to much attention. The aim of this study was to identify and compare areas of animal welfare concern for commercial pigs in four different production stages: (1) gestating sows and gilts; (2) lactating sows; (3) piglets; and (4) weaner-to-finisher pigs. One welfare assessment protocol was developed for each stage, comprising of between 20 and 29 animal welfare measures including resource-, management- and animal-based ones. Twenty-one Danish farms were visited once between January 2015 and February 2016 in a cross-sectional design. Experts (n = 26; advisors, scientists and animal welfare controllers) assessed the severity of the outcome measures. This was combined with the on-farm prevalence of each measure and the outcome was used to calculate areas of concern, defined as measures where the median of all farms fell below the value defined as 'acceptable welfare.' Between five and seven areas of concern were identified for each production stage. With the exception of carpal lesions in piglets, all areas of concern were resource- and management-based and mainly related to housing, with inadequate available space and the floor type in the resting area being overall concerns across all production stages. This means that animal-based measures were largely unaffected by perceived deficits in resource-based measures. Great variation existed for the majority of measures identified as areas of concern, demonstrating that achieving a high welfare score is possible in the Danish system.

Automatic monitoring and detection of tail-biting behavior in groups of pigs using video-based deep learning methods

Automated monitoring of pigs for timely detection of changes in behavior and the onset of tail biting might enable farmers to take immediate management actions, and thus decrease health and welfare issues on-farm. Our goal was to develop computer vision-based methods to detect tail biting in pigs using a convolutional neural network (CNN) to extract spatial information, combined with secondary networks accounting for temporal information. Two secondary frameworks were utilized, being a long short-term memory (LSTM) network applied to sequences of image features (CNN-LSTM), and a CNN applied to image representations of sequences (CNN-CNN). To achieve our goal, this study aimed to answer the following questions: (a) Can the methods detect tail biting from video recordings of entire pens? (b) Can we utilize principal component analyses (PCA) to reduce the dimensionality of the feature vector and only use relevant principal components (PC)? (c) Is there potential to increase performance in optimizing the threshold for class separation of the predicted probabilities of the outcome? (d) What is the performance of the methods with respect to each other? The study utilized one-hour video recordings of 10 pens with pigs prior to weaning, containing a total of 208 tail-biting events of varying lengths. The pre-trained VGG-16 was used to extract spatial features from the data, which were subsequently pre-processed and divided into train/test sets before input to the LSTM/CNN. The performance of the methods regarding data pre-processing and model building was systematically compared using cross-validation. Final models were run with optimal settings and evaluated on an independent test-set. The proposed methods detected tail biting with a major-mean accuracy (MMA) of 71.3 and 64.7% for the CNN-LSTM and the CNN-CNN network, respectively. Applying PCA and using a limited number of PCs significantly increased the performance of both methods, while optimizing the threshold for class separation did result in a consistent but not significant increase of the performance. Both methods can detect tail biting from video data, but the CNN-LSTM was superior in generalizing when evaluated on new data, i.e., data not used for training the models, compared to the CNN-CNN method.

Individual behavioral correlates of tail biting in pre-finishing piglets

Introduction

Tail biting is a widespread problem in pig production systems and has a negative impact on both animal welfare and farm income. This explorative study aims to validate how tail biting is related to general behaviors at the individual level and explore whether these behaviors are related to a particular type of tail biting: two-stage, sudden-forceful, obsessive, or epidemic.

Methods

This research was conducted in a standard commercial setting where 89 tail-docked pre-finishing piglets divided into 8 groups were observed 4 days per week from 5 to 8 weeks of age. Each piglet was observed for a total of 160 min using continuous focal sampling. Ten individual behaviors were recorded based on the general behaviors expected to be linked to giving tail biting (PCA1), receiving tail biting (PCA2), and tail biting damage (PCA3). These PCAs were assembled and related to tail biting given, tail biting received, and tail biting lesions.

Results

Tail biting did not lead to major damage on the piglets' tail at 8 weeks of age but was observed 420 times, where most of the individuals (72%) were categorized as "biters and victims." When relating PCA1 with tail biting given, piglets that gave more tail biting showed more "active exploration." When relating PCA2 with tail biting received, piglets receiving more tail biting were more "explored while active" and "attacked and explored." When relating PCA2 with tail biting lesions, piglets presenting lesions showed more "agonism." Surprisingly, tail biting lesions were not significantly related to PCA3. The relationship between explorative behaviors and tail biting indicates that the pre-damage stage of two-stage tail biting was the predominant tail biting type, while the damaging stage was likely incipient. The relationship between tail biting and aggression, as well as the minor tail lesions observed suggest that sudden-forceful tail biting was probably present even though it was rarely seen. Obsessive and epidemic tail biting were not observed.

Discussion

This study demonstrates that studying tail biting at the individual level helps to identify the type of tail biting present. This gives directions to farmers for applying appropriate measures to prevent the development of tail biting behavior in piglets.

Global and Brazilian Scenario of Guidelines and Legislation on Welfare in Pig Farming

Simple Summary

As with all production animals, pigs need environments suitable for their species, which results in less stress and suffering and more productivity. Therefore, there are quality standards and good management and production practices that must be followed to ensure their well-being. In this sense, over the last few years, many advances have been made, banning or restricting practices capable of causing suffering to animals in most producing countries. This review seeks to explore current global and Brazilian regulations on good production practices in swine farming.

Abstract

The evolution of scientific knowledge regarding animal sentience, together with the growing concerns of consumers regarding current production models, has brought with it the responsibility of reviewing many practices carried out in industrial swine farming, with the purpose of improving the life quality of animals throughout the entire production cycle. In this sense, many initiatives have been taken by European Union, OIE and other countries to abolish questionable practices from an animal welfare point of view, being signed through legislation or normative instructions, which guide governments and companies on the best practices to be adopted. Among the main changes that have taken place in swine farming are the ban or reduction in the use of cages for sows, restrictions on the age at weaning, ban on painful procedures such as surgical castration, tail and teeth clipping, as routine procedures or without the use of anesthesia/analgesia. In addition, these acts also prescribe practices that must be adopted in order to respect the natural behavior of animals, such as the use of environmental enrichment. This review aims to address the main advances made over the last few years in the protection of swine, as well as Brazilian initiatives in this regard.

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.

Effect of Varying Levels of Dietary Tryptophan on Aggression and Abnormal Behavior in Growing Pigs

Body lesions, resulting from tail-biting and ear-biting, can result in decreased health and welfare in pigs. Tryptophan, an indispensable amino acid, is needed to support protein deposition, and the synthesis of the neurotransmitter serotonin, which is important to mood, sleep-wake and eating patterns and might play a role in aggression and abnormal behavior. Two randomized block design studies were conducted to assess the influence of varying dietary tryptophan levels on aggression and abnormal behavior in 8-week-old pigs. Six diets were formulated which met or exceeded all nutrient requirements yet differed according to the dietary tryptophan content. The first study included control (100% standardized ileal digestible tryptophan), supplemented (175% standardized ileal digestible tryptophan), and supplement-plus (250% standardized ileal digestible tryptophan) experimental diets, while the second study included deficient (80% standardized ileal digestible tryptophan), adequate control (105% standardized ileal digestible tryptophan), and extra-tryptophan (130% standardized ileal digestible tryptophan) experimental diets. Concentrations of plasma tryptophan and large neutral amino acids (tyrosine, isoleucine, leucine, valine, and phenylalanine) were analyzed using ultra-performance liquid chromatography and the tryptophan to large neutral amino acid ratio was calculated. Analysis for time active, lying, and engaging in aggressive interactions was carried out using 10-min scan samples to determine behavioral time budgets of the pigs on different experimental diets. Pigs fed diets with supplemented tryptophan had higher concentrations of both plasma tryptophan and tryptophan to large neutral amino acid ratio compared to the pigs fed the control diet (P < 0.05) in the first study, while no significant differences were detected for plasma tryptophan or the tryptophan to large neutral amino acid ratio in the second study. Diet did not have an effect (P > 0.05) on weight, feed intake or behavior throughout the studies. The results suggest that an increase in dietary tryptophan relative to large neutral amino acids, fed for 29 days, impacts circulating plasma tryptophan and therefore, serotonin concentrations in the pig. Despite an increase in circulating plasma tryptophan in response to an increase in dietary tryptophan in the first study, we failed to see an impact of the dietary treatment on body, tail and ear-biting behavior under the conditions studied.

The Relationship between Carcass Condemnations and Tail Lesion in Swine Considering Different Production Systems and Tail Lengths

Simple Summary

Tail biting is considered a major welfare problem in swine production, associated with relevant financial costs for farmers. The European Union has reaffirmed the prohibition of tail docking practices, with all Member States establishing standards for the protection of pigs as well as measures to reduce the need for tail docking and tail biting prevalence. This research aims to assess the importance of tail lesions (using two different scores) and its influence on carcass condemnations considering different production systems and tail length. According to the results, higher tail lesion scores reflected higher total condemnations rates. An intimate association was encountered between the scarring score and total and local carcass condemnations. Tail length was also significant, with undocked animals presenting higher tail lesions scores. Organic batches reported more total condemnations. This research highlights the importance of tail lesions on carcass condemnations that may also be influenced by docking and type of production. These results suggest that scarred tail tissue should be included in the current tail surveillance program.

Abstract

Tail biting has been recognised as an intractable problem in pig production. This study aims to evaluate tail lesion occurrence in slaughtered pigs and explore the relationship between carcass condemnations and tail lesion considering different production systems and tail lengths and to evaluate the importance of creating a detailed tail score classification that includes scarred lesions. Data on a total of 9189 pigs from 73 batches with different tail lengths (undocked; docked mid-length; fully docked) and from distinct production systems (conventional; conventional antibiotic-free and organic) were collected at a Spanish abattoir. Batches with higher tail lesion scores presented a significantly higher chance of total condemnation and total condemnation due to pyaemia, being even more associated with scarring score. The within-batches probability for local condemnations and local condemnation due to abscesses increased significantly with higher scarring scores. Regarding tail length, docked at mid-length and undocked carcasses presented significantly higher odds to be condemned due to abscess. Organic farms showed a higher probability of total condemnations. This research highlights the importance of tail lesions on carcass condemnations that may also be influenced by docking and type of production. Results suggest that scarring score should be included in the tail surveillance program.

Reduced Stocking Density and Provision of Straw in a Rack Improve Pig Welfare on Commercial Fattening Farms

The aim of this study was to investigate the impact of reduced stocking density in combination with provision of additional enrichment material on pig welfare on-farm. On three growing-finishing farms in Austria, in total 974, 413, and 70 pigs were kept at 1 m²/pig and straw or hay in a rack as additional enrichment material (improved pens, IP; n = 6–38 pens per farm) or in pens complying with the minimum legal requirements of 0.7 m²/pig (control pens, CP; n = 6–37 pens per farm). Behavior as well as skin, tail and ear lesions and pig soiling were assessed at the beginning and in the middle of the fattening period, while performance data were recorded at the end of the fattening period. Data analysis was performed for each farm separately using generalized linear and linear mixed models or Mann-Whitney U-Test. Pigs in IP less frequently manipulated pen mates' ears (Farm 1: Ptreatment*assessment = 0.002; Farm 2: P = 0.002) and body (Farm 1: P = 0.021; Farm 2: P = 0.015) than in CP. Prevalence of skin, tail and ear lesions and soiled pigs did not differ between treatments. In only one farm, average daily weight gain was higher in IP than in CP (Farm 1: P = 0.003). Our findings indicate that increased space allowance and provision of substrate can improve aspects of animal welfare within existing pig fattening systems, without requiring irreversible constructional modifications to the system.

Association Between Tail-Biting and Intestinal Microbiota Composition in Pigs

Tail-biting (TB) in pigs is a serious behavioral disorder. It is an important challenge in swine production as it impacts animal welfare and health and the economics and safety of the pork meat supply chain. To prevent TB, approaches including enrichment material and tail docking are proposed but none are optimal. Nutrition appears to be an important factor in TB behavior, perhaps by modulating the intestinal microbiota (IM). Our aim was to assess the association between TB behavior and IM in pigs through comparisons of IM in groups of biter, bitten and non-biter/non-bitten pigs. Each group composed of 12 pigs was formed at the beginning of the growing/finishing phase based on a target behavior analysis centered on TB behavior for the biter group and a score of damages caused to the tail for the bitten group. Blood and fecal samples were collected from each pig during a TB episode, at time 0, t0, and when the TB episode was considered finished, 4 weeks later, at time 1, t1. Serum cortisol level was determined by ELISA and used as an indicator of stress. The pig's fecal microbiota was analyzed from DNA extracted from freshly collected fecal matter using amplicon sequencing of the V4 hypervariable region of the 16S rRNA gene. Serum cortisol levels were significantly higher in either the biter or bitten pig groups compared to the negative control group (p = 0.02 and p = 0.01, respectively). The microbiota alpha-diversity was not significantly different between all groups, biter, bitten and negative control. Analyses of beta-diversity, however, revealed a significant difference between either the biter or the bitten group in comparison to the non-biter/non-bitten negative control group in terms of structure and composition of the microbiota. Lactobacillus were significantly more abundant in the negative control group compared to the two other groups (p = 0.001). No significant difference was revealed between the biter and bitten groups. Quantitative real-time PCR (qPCR) confirmed that lactobacilli were more abundant in the negative control group. Our study indicates that TB behavior is associated with the IM composition in pigs.

Evidence of Pain, Stress, and Fear of Humans During Tail Docking and the Next Four Weeks in Piglets (Sus scrofa domesticus)

Tail docking is widely performed in pig farms to prevent tail biting. We investigated the consequences of this practice on behavioral indicators of pain and stress, and on the human-piglet relationship during lactation. Within 19 litters, piglets (1–3 days of age) were submitted on day 0 (D0) to docking with a cautery iron (D), sham-docking (S), or no docking (U). Piglets from the D and S groups were observed during the procedure (body movements and vocalizations) and just after, in isolation, during 20 s for body, tail and ear postures as well as ear movements. Piglets from the three treatments were observed in their home pen after docking on D0 and D3 afternoon for body posture, tail posture and movements. Piglets from the D and U groups were observed on D6, D12, D19, and D26 in their home pen for oral behavior, body, and tail posture. Tail damage and tear staining were scored on D5, D11, D18, and D25. A 5-min motionless human test was performed on D14. During the procedure, D piglets screamed more and with a higher intensity (P < 0.05) than S piglets (n = 48–50). Just after docking, D piglets held their ears in a posture perpendicular to the head-tail axis and changed their ear posture more often (P < 0.05). Between D6 and D26, D piglets kept their tail immobile (P < 0.001) and in a horizontal position (P < 0.01) more often than U piglets (n = 45–47). Between D11 and D25, U piglets had higher scores for tail damage and damage freshness than D piglets (0.09 < P < 0.02) whereas tear-stain score was similar. In the human test, D piglets interacted later with an unfamiliar human than U piglets (P = 0.01, n = 18/group). Present data indicate signs of acute pain and stress in piglets due to docking during the procedure itself and adverse consequences throughout lactation thereafter, including on their relationship with humans. On the other hand, the presence of tail lesions shows that undocked piglets are subject to more tail biting, even before weaning.

Effect of pen design on tail biting and tail-directed behaviour of finishing pigs with intact tails

Tail biting is a welfare and economical concern in modern pig production. One common preventive measure used throughout the world is tail docking, which is generally considered one of the most effective methods for limiting tail biting. However, tail docking is a painful mutilation and systematic tail docking is not allowed in the EU. Therefore, the aim was to compare pig behaviour and the prevalence of tail biting in finishing pigs with intact tails housed in two different pen designs under Danish commercial conditions. PEN1 was a traditional Danish pen and PEN2 was inspired by Swedish finisher pen design and had a larger proportion of solid floor area (PEN1: 1/3 and PEN2: 2/3), reduced group size (PEN1: 15 and PEN2: 12), increased space allowance per head (PEN1: 0.7 m2 and PEN2: 0.89 m2) and straw allocated on the floor (PEN2) whereas straw was provided in a straw rack in PEN1. Tail damage observations were carried out daily by the stockperson and every 2 weeks one trained research technician assessed tail damages according to a tail scoring system. Tail lesions were observed in 51% of PEN1 and in 11% of PEN2 (P < 0.001). PEN1 had higher prevalence of tail damages than PEN2 (23% v. 5%, P < 0.001). Behavioural observations were carried out by the use of video recordings. Pigs in PEN2 tended to spend more time on tail-directed behaviour than pigs in PEN1 (P = 0.07), whereas pigs in PEN1 tended to spend more time on ear-directed behaviour (P = 0.08). Pigs in PEN2 spent more time on straw-directed behaviour compared to pigs in PEN1 (P < 0.001). Pen design did not affect time spent on other penmate-directed behaviour. In addition, the level of welfare between the two pen designs was compared using the Welfare Quality® protocol. PEN2 received an overall score of 'excellent' while PEN1 scored 'enhanced'. PEN2 scored higher on all principles besides 'good health', where PEN1 scored better on lameness and wounds. The main measurements accounting for the differences were water supply, huddling, tail biting, social behaviour and fear of humans. In conclusion, the combination of increased space allowance, increased area of solid flooring, straw allocated onto the floor and reduced group size (PEN2) resulted in fewer tail damaged pigs and a better overall welfare assessment, despite a tendency for more tail-directed behaviour.

Effects of tail docking and/or teeth clipping on behavior, lesions, and physiological indicators of sows and their piglets

To evaluate effects of tail docking and/or teeth clipping on sows and their piglets, a total of 24 sows and their 302 piglets at 3 days of age were randomly allocated to one of four treatments: teeth clipping and tail docking (TCTD), teeth clipping (TC), tail docking (TD), or intact teeth and tail (Intact). Behavior of piglets and sows, lesions on the body and tail of piglets and sows' teats were inspected. Heart rates of processed piglets were increased (p < .01) during the procedures. Teeth clipping decreased body surface temperature (p < .01) of piglets during and after the procedures but tail docking did not (p > .01). Processed piglets spent more (p < .05) time lying alone and playing/fighting than sham-processed piglets. Tail docked piglets spent less (p < .01) time standing than tail sham-docked piglets. Intact teeth increased (p < .05) the avoidance behaviors of sows. Teeth clipping decreased (p < .05) the lesion scores on the anterior, middle, and posterior teats. Taken together, piglet teeth clipping had more impact on sows and their piglets than tail docking did in the lactation period based on our findings.

Docking piglet tails: How much does it hurt and for how long?

Tail docking in pigs has the potential for evoking short- as well as long-term physiological and behavioural changes indicative of pain. Nonetheless, the existing scientific literature has thus far provided somewhat inconsistent data on the intensity and the duration of pain based on varying assessment methodologies and different post-procedural observation times. In this report we describe three response stages (immediate, short- and long-term) through the application of vocalisation, behavioural and nociceptive assessments in order to identify changes indicative of potential pain experienced by the piglets. Furthermore, we evaluated the following procedural differences: (1) cautery vs. non-cautery docking; (2) length of tail removal. Sound parameters showed a significantly greater call energy and intensity exhibited by docked vs. sham-docked piglets (P<0.05). Observations of general activity of the animals in a test situation failed to detect a difference among treatments (P>0.05) up to 48h post-tail docking. Similarly, no difference in mechanical nociceptive thresholds indicative of long term pain was observed at 17weeks following neonatal tail docking (P>0.05). The present results highlight the potential for the use of measures of vocalisation to detect peri-procedural changes possibly associated with evoked pain. Nonetheless, activity and nociceptive measures failed to identify post-docking anomalies, suggesting that alternative methodologies need to be implemented to clarify whether tail docking is associated with short- and long-term changes attributable to pain experienced by the piglets.

Determination of stable reference genes for RT-qPCR expression data in mechanistic pain studies on pig dorsal root ganglia and spinal cord

RNA expression levels for genes of interest must be normalised with appropriate reference or "housekeeping" genes that are stably expressed across samples and treatments. This study determined the most stable reference genes from a panel of 6 porcine candidate genes: beta actin (ACTB), beta-2-microglobulin (B2M), eukaryotic elongation factor 1 gamma-like protein (eEF-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), succinate dehydrogenase complex subunit A (SDHA), Ubiquitin C (UBC) in sacral dorsal root ganglia and spinal cord samples collected from 16 tail docked pigs (2/3rds of tail amputated) 1, 4, 8 and 16weeks after tail injury (4 pigs/time point). Total RNA from pooled samples was measured by SYBRgreen real-time quantitative PCR. Cycle threshold values were analysed using geNorm, BestKeeper and NormFinder PCR analysis software. Average expression stability and pairwise variation values were calculated for each candidate reference gene. GeNorm analysis identified the most stable genes for normalisation of gene expression data to be GAPDH>eEF-1>UBC>B2M>ACTB>SDHA for dorsal root ganglia and ACTB>SDHA>UBC>B2M>GAPDH>eEF-1 for spinal cord samples. Expression stability estimates were verified by BestKeeper and NormFinder analysis. Expression stability varied between genes within and between tissues. Validation of most stably expressed reference genes was performed by normalisation of calcitonin gene related polypeptide beta (CALCB). The results show similar patterns of CALCB expression when the best reference genes selected by all three programs were used. GAPDH, eEF-1 and UBC are suitable reference genes for porcine dorsal root ganglia samples, whereas ACTB, SDHA and UBC are more appropriate for spinal cord samples.

Provision of straw by a foraging tower -effect on tail biting in weaners and fattening pigs

BACKGROUND

Straw is one of the most effective rooting materials to reduce tail biting in pigs. A so-called foraging-tower (FT) provides only small quantities of straw compatible with liquid manure systems. The focus of the present study was on the effect of providing straw by FT in order to prevent tail biting in tail docked pigs. Four consecutive batches of 160 pigs, randomly divided into a straw (SG) and a control group (CG) were followed up from weaning to slaughter.

RESULTS

Tail wounds (Score ≥ 2) were detected in 104 out of 12,032 single observations (SG n = 48; CG n = 56) in 9 pens (SG n = 4/32; CG n = 5/32) mainly focused on the fattening period of batch 2 due to a failure in the ventilation system. No significant differences concerning the distribution of Score ≥ 2 in pens of the SG and CG could be identified. Bite marks (Score 1) were documented in 395 observations at animal level (SG n = 197, CG n = 198) in all batches. In the nursery period, the air velocity significantly increased the chance that at least one pig per pen and week showed a tail lesion score ≥1 (p = 0.024). In the fattening period ammonia concentration was positively associated with tail lesions (p = 0.007). The investigation of blood samples revealed infections with Mycoplasma hyopneumoniae in all batches and a circulation of Porcine Reproductive and Respiratory Syndrome Virus (NA-vaccine strain) and Porcine Circovirus Type 2 in two batches each. The average daily straw consumption was 3.5 g/pig (standard deviation (SD) = 1.1) during the rearing period and 31.9 g/pig (SD = 7.7) during the fattening period.

CONCLUSION

Due to the low prevalence of tail biting in all batches the effect of the FT tower could not be evaluated conclusively. The operation of the FT with an average daily straw consumption of 3.5 g/pig (SD = 1.1) during the rearing period and 31.9 g/pig (SD = 7.7) during the fattening period did not affect the weight gain. Exploratory behaviour seems to cause bite marks (score 1), which do not necessarily result in tail biting. The main outbreak of tail biting was probably triggered by a failure of the ventilation system, which resulted in a number of climatic and air quality changes including higher ammonia concentrations and sudden temperature changes.

A survey of straw use and tail biting in Swedish pig farms rearing undocked pigs

Background

Tail biting is a common problem in intensive pig farming, affecting both welfare and production. Although routine tail docking is banned within the EU, it remains a common practice to prevent tail biting. Straw as environmental enrichment has been proposed as an alternative to tail docking, but its effectiveness against tail biting and function in manure handling systems have to be considered. The aim of the study was to survey how pigs with intact tails are raised and how tail biting is handled in Sweden, where tail docking is banned through national legislation. The study emphasises straw usage and its association with tail biting pigs and problems in the manure handling system. The expectation is that this information could be conveyed to the rest of the EU to reduce the need for tail docking.

Results

In a telephone survey of randomly selected Swedish pig farmers (46 nursery and 43 finishing pig units) with at least 50 sows or 300 finishing places, it was found that straw was used by 98% of the farmers. The median daily straw ration provided was 29 g/pig for nursery and 50 g/pig for finishing pigs in systems with partly slatted flooring. The reported prevalence of tail biting was 1.6% at slaughter. The majority of farmers reported that they never had manure handling problems caused by straw (56% of nursery units and 81% of finishing pig units). A proportion of farmers (37%) also provided with additional material apart from straw on some occasions, which may have affected tail biting prevalence and manure handling problems.

Conclusions

Swedish farmers rear undocked pigs without large problems with tail biting. Straw is the main manipulable material used, and additional manipulable material is used to various extents. The low incidence of straw obstructing the manure handling systems implies that it is indeed possible to use straw in partly slatted flooring systems, reducing the need for tail docking. The impact of using additional manipulable material is unknown and requires more investigation to separate the impact of such material from the impact of straw.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-016-0266-8) contains supplementary material, which is available to authorized users.

Comparison of neural histomorphology in tail tips from pigs docked using clippers or cautery iron

Tail docking of pigs is commonly performed to reduce the incidence of unwanted tail-biting behaviour. Two docking methods are commonly used: blunt trauma cutting (i.e. using side clippers), or cutting and concurrent cauterisation using a hot cautery iron. A potential consequence of tail amputation is the development of neuromas at the docking site. Neuromas have been linked to neuropathic pain, which can influence the longer-term welfare of affected individuals. To determine whether method of tail docking influences the extent of neuroma formation, 75 pigs were allocated to one of three treatments at birth: tail docked using clippers; tail docked using cautery iron; tail left intact. Tail docking was performed at 2 days of age and pigs were kept under conventional conditions until slaughter at 21 weeks of age. Tails were removed following slaughter and subjected to histological examination. Nerve histomorphology was scored according to the following scale: 1=discrete well-organised nerve bundles; 2=moderate neural proliferation and disorganisation affecting more than half of the circumference of the tail; 3=marked neural proliferation to form almost continuous disorganised bundles or non-continuous enlarged bundles compressing the surrounding connective tissue. Scores of 2 or 3 indicated neuroma formation. Scores were higher in docked pigs than undocked pigs (P<0.001), but did not differ between pigs docked using clippers and those docked using cautery (P=0.23). The results indicate that tail docking using either clippers or cautery results in neuroma formation, thus having the potential to affect long-term pig welfare.

[Keeping pigs with undocked tails on conventionally producing farms. A feasibility study]

OBJECTIVE

In this feasibility study, weaning and fattening pigs with undocked and docked tails were kept simultaneously on four conventionally producing farms in Lower Saxony, Germany. It was the aim of the study to test management recommendations to avoid and reduce tail biting under practical conditions.

MATERIAL AND METHODS

Before stocking, the farm-specific risk factors for tail biting had been analyzed and, if possible, reduced. Furthermore, on every farm, individual preventive measures, for example, additional pen enrichments and feed additives had been adopted. The farmers had been trained in animal observation, recognition of tail biting prior to outbreaks and measures to be taken when tail biting occurred. The tails of the pigs were examined daily by the farmer and every second week by the first author. Additionally, carcass characteristics were documented and analyzed.

RESULTS

Tail biting was observed in every batch on every farm during the rearing period. Combining data from all the farms, a mean of 53.5% of pigs with undocked tails could enter the fattening period without tail lesions. At the end of fattening, only 24.2% of the undocked slaughter pigs had intact tails. Additionally, in the group with undocked tails, mortality was significantly increased (p = 0.0104) in comparison with the control group and abscesses were detected significantly more frequently in carcasses of undocked pigs (p < 0.0001).

CONCLUSION

As a consequence of these results, a transition period of several years is recommended to give farmers the opportunity to learn step by step how to maintain animals with undocked tails and to prevent animal suffering due to tail biting.

The effect of social isolation, gender and familiarity with the experimental procedure on tests of porcine nociceptive thresholds

OBJECTIVE

To investigate the effects of habituation and isolation on mechanical nociceptive thresholds in pigs at the pelvic limbs and at the tail.

STUDY DESIGN

Prospective randomized multifactorial study.

ANIMALS

Thirty-two healthy castrated male (experiment 1), and 12 castrated male and 12 female (experiment 2) Danish Landrace×Yorkshire pigs, weighing 63.5±0.8 kg and 55.4±0.6 kg (the mean±SD, experiment 1 and 2, respectively).

METHODS

Mechanical nociceptive thresholds were quantified with a von Frey anesthesiometer applied to two distinct anatomical regions (tail and pelvic limbs). Pigs receiving the mechanical challenge in the pelvic limbs were tested inside a cage, whereas pigs exposed to stimuli at the tail region were tested in an open arena. For both experiments, the effect of familiarity to the procedure was evaluated by comparing thresholds of nociception in habituated versus naïve pigs. The presence of a companion animal was also evaluated in pigs receiving stimuli at the pelvic limbs.

RESULTS

Pigs tested inside the cage were affected by the habituation to the procedure as indicated by the increase in willingness and time spent by the animals in the test cage. This effect was reflected in the lower mechanical nociceptive thresholds (medians with 25-75 percentiles) recorded for familiar pigs compared with naïve animals [495 g (302-675) versus 745 g (479-1000), respectively; p=0.026]. Mechanical nociceptive thresholds measured at the tail of the pigs in the open arena were not affected by the familiarity of the animals with the experimental procedure.

CONCLUSIONS AND CLINICAL RELEVANCE

The current results reiterate the value of habituation in research involving animal behaviour. Further characterization of the methodology is needed to allow its application in the evaluation of clinical conditions in pigs.