Tag Archives: Tail lesions

Survey on straw use and tail biting on Swedish pig farms

Wallgren, T. R. Westin and S. Gunnarsson, 2016.  A survey of straw use and tail biting in Swedish pig farms rearing undocked pigs. Acta Veterinaria Scandinavica 58:84.

Abstract

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.

Straw survey in Sweden (3 conference abstracts)

A survey of straw use and tail biting in Swedish undocked pig farms
ICPD 2016, 20-23 June 2016, Wageningen (oral presentation)
T. Wallgren, R. Westin, S. Gunnarsson
Swedish University of Agricultural Sciences, Department of Animal Environment and Health, Skara, Sweden

Abstract

Tail biting is a common problem in todays’ pig production, affecting production and welfare. As tail biting behaviour is more prominent in systems with no or limited access manipulable material, it has been considered related to exploratory behaviours. Tail docking, commonly used as tail biting prevention, is a painful procedure that can decrease pig welfare does not eliminate the tail biting behaviour. Although tail docking is not accepted as a routine procedure according to the EU Directive 2008/120/EC it is still a common practise within the EU, which is why other measures to reduce tail biting behaviour are needed. In Sweden, tail docking is banned and tail biting must be reduced otherwise. Furthermore, Swedish legislation banned fully slatted floors and demands pigs to have access to manipulable material. In order to investigate the prevalence of tail biting in Sweden and the relationship with provision of straw, we performed a telephone survey in nursery (n=46) and finishing pig (n=43) farms. Farmers were interviewed regarding straw usage (e.g. daily ratios) and tail biting (e.g. frequency). All participating farmers gave access to manipulable material and 98% used straw. The median straw ration reported by farmers was 29g/pig/day (min: 8g, max: 85g) in nursery and 50g/pig/day (9g, 225g) in finishing farms when excluding deep litter systems. Farmers reported having observed tail bitten pigs, at any time, in 50% of nursery and 88% of finishing pig farms. Of these, tail bitten pigs were reported to be found ≤2 times/year (78%), 3-6 times/year(17%) or monthly (4%) in nursery and ≤2 times/year (21%), 3-6 times/year (37%), monthly (34%) or weekly (8%) in finishing farms. Finishing farmers reported on average 1.6% tail bitten pigs/batch (0.1-6.5%), which is in line with abattoir data. Spearman rank correlation was used for statistical analysis. Increased straw ration was correlated with decreased reported tail biting frequency in finishing farms (r=-0.39, P=0.03, n=31), and a tendency for this was found in nursery farms (r=-0.33, P=0.08, n=29) when deep litter systems were included. In finishing farms, excluding deep litter systems, an increased tail biting frequency observed by farmers was correlated to the percentage of tail bitten pigs (r=0.64, P=<0.001, n=33), indicating that an increased frequency of tail biting reported may be associated with more pens affected at outbreaks. Even though provided straw rations were quite small (i.e. 30-50 g/pig/day), this amount of straw may provide pigs with enough occupation to limit tail biting outbreaks. We conclude that tail biting can be kept at a low level (ca 2%) in partly slatted flooring systems, without tail docking, by supplying straw.

Raising undocked pigs: straw, tail biting and management
ISAE 201612-15 July 2016 (poster presentation, see below)
Torun Wallgren, Rebecka Westin and Stefan Gunnarsson
Swedish University of Agricultural Sciences, Department of Animal Environment and Health, Skara, Sweden

Abstract

Tail biting in pigs is common in pig production and has been suggested correlated to several behaviours. It is associated with reduced welfare and production losses. A common practice to reduce tail biting within EU is tail docking where part of the tail is removed; a painful procedure that does not eliminate the behaviour. According to the EU Directive 2008/120/EC routine tail docking is banned and other measures to reduce tail biting must replace docking. An alternative is to improve the pig environment by using straw and thus decrease development of tail biting. Straw usage has been difficult to implement since it is argued that straw provision is incompatible with fully slatted floors. In Sweden, tail docking and fully slatted floors are completely banned through national legislation. Furthermore, it is a legal requirement that pigs should have access to manipulable material. The implementation of straw usage in Swedish farms was investigated in a telephone survey to study straw usage and farmers’ opinion on straw impact on tail biting and farm management. A total of 46 nursery and 43 finishing farmers were interviewed, all reporting providing pigs with enrichment material, most commonly straw (98%). Median straw rations provided in systems with partly slatted floor was 29 g/pig/day (8-85 g) in nursery and 50 g (9-225 g) in finishing farms. Straw was the only manipulable material in 50% of nursery and 65% of finishing farms while remaining farms used additional material, most commonly wood shavings (65%). ‘Toys’, e.g. balls and ropes, were used by 13% of nursery and 16% of finishing farmers as a supplement to other manipulable material. Of these, 62% only provided these ‘toys’ occasionally, e.g. at re-grouping or when tail biting had been observed. Problems in the manure handling systems caused by straw had occurred in 32% of the farms, of these 25% had problems at yearly and 7% monthly, or more seldom (58%). Tail biting had been observed in the production at least once by 50% of nursery and 88% of finishing farmers, an average of 1.6% finishing pigs were reported tail bitten per batch (0.1-6.5). Tail biting was observed ≤twice/year (78%) 3-6 times/yr (17%) and monthly (4%) by nursey and ≤2 times/yr (21%), 3-6 times/yr (37%), monthly (34%) and weekly (8%) by finishing farmers. The provided amounts of straw seem to be sufficient to keep tail biting at a low level in undocked pig herds (<2%/batch). The low incidence of straw obstruction in manure handling systems reported also implies that straw usage at this rate 30-50 g/pig/day) is manageable in pig production systems.

Production of undocked pigs, a survey of farmers’ experiences
EAAP Annual Meeting, 29 August – 2 September 2016, Belfast (oral presentation)
T. Wallgren, R. Westin, S. Gunnarsson
Swedish University of Agricultural Sciences, Department of Animal Environment and Health, Skara, Sweden

Abstract

Tail biting is a common cause for reduced welfare and production rates within commercial pig production and is more prominent in barren environments. Using enrichment as straw has been shown to reduce tail biting behavior and thus reduce need for tail docking. Implementation of straw in practice has however partly default since it is argued that straw will cause obstruction in the manure handling systems. Sweden has a long tradition of rearing undocked pigs with access to straw due to national legislation banning docking and fully slatted floors while demanding access to manipulable material for pigs. We surveyed 60 randomly selected Swedish nursery and finishing pig farmers’ usage of straw and their opinions on straw impact on tail biting and manure handling management. All farmers provided manipulable material, 98% straw. In 50% of nursery and 35% of finishing farms the straw was complemented with material such as wood shavings. Straw rations were 29g/pig/day (8-85g) in nursery and 50g (9-225g) in finishing farms. Straw was commonly chopped (76%) to a mean length of 6 cm (1-10) in nursery and 8 cm (1-20) in finishing farms. Straw causing problems in the manure handling system occurred in 32% of the farms who experienced this yearly (25%) or monthly (7%). Most common causes were straw making the slurry sluggish, stacked in pivot or blocking slats. The low incidences of problems indicate current systems are able to cope with presented straw rations. Tail biting had been seen at least one time ever in 50% of nursery and 88% of finishing farms. Frequency of observed tail biting was ≤twice/year (78%) 3-6 times/yr (17%) and monthly (4%) by nursey and ≤ 2 times/yr (21%), 3-6 times/yr (37%), monthly (34%) and weekly (8%) by finishing farmers. An average of 1.6 (0.1-6.5) finishing pigs were reported tail bitten each batch. In partly slatted flooring systems a correlation was found between increased tail biting frequency and percentage of reported tail bitten pigs (r=0.64, P= <0.0001, n=38) (Spearman Rank correlation). The limited tail biting problems indicate that straw usage at this level is enough to prevent major tail biting outbreaks in undocked pigs.

Poster straw survey Sweden

Tail-in-mouth behaviour in weaned piglets

Can tail-in-mouth behaviour in weaned piglets be predicted by behaviour and performance? By Camilla Munsterhjelm, Mari Heinonen, Anna Valros. In: Appl. Anim. Behav. Sci.

Abstract

This study aimed to identify characteristics of pigs performing tail-in-mouth behaviour (TIM; P, n =34), their recipients (R, n =23) and neutral penmates (N, n =31) at two occasions, the first being at weaning (4 weeks of age) before TIM was observed in the pen and the second being at 9 weeks of age when TIM had emerged, but no clinical tail lesions were observed. The groups (n =22) were formed by siblings, two gilts and two castrates. Behaviour was analysed as 24-hour time budgets and continuously sampled during 30minutes of the active part of the day. Category (P, R, N) effects were analysed at individual and (directed) dyad level. P was born significantly smaller than R, but the difference had disappeared at 4 weeks. Growth or sex distribution did not differ between categories. Category differences in performed behaviour were evident at 4 weeks of age, when P showed more overall activity and environmental exploration as compared to R, as well as more bouts of tail-nosing than N. Different aspects of behaviour changed in the different categories between 4 and 9 weeks of age. In P social activity increased significantly and went from no preference at 4 weeks to a significant preference for social actions for R over N at 9 weeks. N was socially passive at 9 weeks while receiving more social behaviour than the other categories. These differences in behaviour suggest that the categories represented different phenotypes of pigs.

Effects of administration of a local anaesthetic and/or an NSAID and of docking length on the behaviour of piglets during 5 h after tail docking

Effects of administration of a local anaesthetic and/or an NSAID and of docking length on the behaviour of piglets during 5 h after tail docking

By M.S. Herskin, P. Di Giminiani, K. Thodberg, 2016. Research in Veterinary Science 108: 60–67.

Highlights

  • Lidocain reduced signs of procedural pain during tail docking in piglets but did not affect behaviour during 5 h after the procedure.
  • Meloxicam had only very marginal effects on behaviour of the piglets during and up to 5 h after tail docking.
  • Tail docking led to behavioural changes throughout the 5 h observation period.
  • Tail docking length affected procedural and post-procedural behaviour of the piglets.

Abstract

In many countries, piglets are tail docked to prevent tail biting. The aim of this study was 1) to evaluate the efficacy of a local anaesthetic and/or NSAID to reduce pain caused by tail docking; and 2) to examine interactions with docking length. This was examined in 295 piglets docked by hot iron cautery 2–4 days after birth and based on behaviour during docking as well as the following 5 h. The study involved three main factors: local anaesthetic (Lidocain), NSAID (Meloxicam) and docking length. Either 100%, 75%, 50% or 25% of the tails were left on the body of the piglets. Irrespective of the tail length, tail docking led to signs of procedural pain, which could be reduced by administration of Lidocain. Preemptive use of Meloxicam did not affect the signs of procedural pain. The results show that tail docking led to behavioural changes throughout the 5 h observation period indicating that effects of this management routine are more persistent than earlier suggested, and suggesting that docking length may influence the post-surgical behaviour of piglets. By use of the present sites of injection and dosages, neither local anaesthetic nor NSAID had marked effects on post-surgical behavioural changes induced by tail docking. Hence, if tail docking is to be performed, more research is needed in order to develop practical methods for on-farm piglet pain relief.

Agent-based modelling in applied ethology: An exploratory case study of behavioural dynamics in tail biting in pigs

Agent-based modelling in applied ethology: An exploratory case study of behavioural dynamics in tail biting in pigs. By Iris J.M.M. Boumans, Gert Jan Hofstede, J. Elizabeth Bolhuis, Imke J.M. de Boer, Eddie A.M. Bokkers. 2016. Applied Animal Behaviour Science

Abstract

Understanding behavioural dynamics in pigs is important to assess pig welfare in current intensive pig production systems. Agent-based modelling (ABM) is an approach to gain insight into behavioural dynamics in pigs, but its use in applied ethology and animal welfare science has been limited so far. We used ABM in a case study on tail biting behaviour in pigs to explore the use of ABM in gaining more insight into emergent injurious pig behaviour and related welfare issues in intensive production systems. We developed an agent-based model in Netlogo 5.1.0 to simulate tail biting behaviour of pigs housed in conventional pens in groups of 10. Pigs in the model started as neutral pigs (not involved in biting incidents), but could change into a biter, victim, or both biter and victim. Tail biting behaviour could emerge when pigs were unable to fulfil their internal motivation to explore. The effects of a redirected exploratory motivation, behavioural changes in victims and preference to bite a lying pig on tail biting patterns were tested in our model. The simulations with the agent-based model showed that coincidence in development of a redirected exploratory motivation can lead to tail biting behaviour in pigs and can explain the strong variations in incidence of tail biting behaviour observed in conventionally housed pigs. Behavioural changes in victims and preference to bite a lying pig seem to be of minor importance in the causation of tail biting patterns. The behavioural time budget of a pig might be an important factor in predisposing pigs to or preventing them from becoming a tail biter or a victim. ABM showed to be useful in analysing behavioural dynamics and welfare issues. An advantage for ABM in applied ethology is the availability of data from empirical studies.

On-farm tail biting prevention in long-tailed pigs – results from a producer questionnaire in Finland

On-farm tail biting prevention in long-tailed pigs – results from a producer questionnaire in Finland. By Valros, A., C. Munsterhjelm, L. Hänninen, T. Kauppinen, M. Heinonen, 2016. Royal Dublin Society: Abstracts book of the 24th International Pig Veterinary Society (IPVS) Congress, Dublin, Republic of Ireland 7-10th June 2016. p. 144.

Abstract

Introduction: Tail biting is a serious welfare problem in pigs, causing substantial economic losses. In the majority of the EU countries, tail docking is used to reduce the incidence of tail biting. However, many of the risk factors for tail biting are related to suboptimal management, and tail biting can be reduced by corrective management decisions. There are few studies on which preventive measures producers themselves value as most important.

Materials and Methods: A questionnaire was distributed via slaughterhouse webpages in 2015. Producers were asked to score the importance of handling different tail-biting risk factors on their own farms, as well as about which manipulable materials they use, and find efficient. In addition, we asked about their opinions on tail biting and tail docking. A total of 70 producers replied, 54 of these replies were regarding fattening pigs, and 16 regarding weaned pigs. The size of the pig units varied between 100 and 6400 pigs, with an average of 1307 pigs. Finland banned tail docking in 2003, so all farms raised long-tailed pigs only.

Results: On average, the producers reported a prevalence of tail biting of 2,3% on their farms, which corresponds well with values reported at Finnish abattoirs. Most producers found tail biting not to be a big problem on their farms and 62% of the farmers found it very unlikely that they would raise tail docked pigs even if it was legal in Finland. The more tail biting reported on the farm, the more problematic the farmers found tail biting, and the more prone they were to say they would probably tail dock if they were allowed to. According to the Finnish producers, the most important factor to prevent tail biting is that there is enough feeding space for the pigs. Altogether, four feeding-related risk factors were included in the top-10 measures to prevent tail biting. Also pig health was considered very important, as well as a good quality of piglets, and controlling air movements in the pen. Straw, newspaper, hay and cardboard were considered the most efficient manipulable materials to prevent tail biting. If tail biting has already started in the pen, the producers ranked identifying and removing the tail biter from the pen as most important, followed by adding bedding-type manipulable materials.

Conclusion: The results are partly in accordance with experimental and epidemiological studies on risk factors for tail biting, but the high focus on feeding-related and health factors is interesting. Finnish farmers appear to handle the tail docking ban well, and do not, on average, find tail biting a very serious problem.

Feeding behaviour and performance in relation to injurious tail biting in boars – a longitudinal study

Feeding behaviour and performance in relation to injurious tail biting in boars – a longitudinal study. By Munsterhjelm, C., J. Nordgreen, M. Heinonen, A. M. Janczak, A. Valros. 2016. Royal Dublin Society: Abstracts book of the 24th International Pig Veterinary Society (IPVS) Congress, Dublin, Republic of Ireland 7-10th June 2016. p. 627.

Abstract

Introduction: Automatically collected feeder data may be used to predict tail biting in finisher pigs.

Materials and Methods: Pen-level feeding behaviour and growth were investigated in relation to injurious tail biting (ITB), defined as visible wounds, from 10 weeks before to 4 weeks after the first ITB case in the pen. The data set included 36 pens of 10-12 intact boars between 43 and 148 kg, with average pen weight at ITB onset between 78 and 137 kg. A tail biting pen (TBPEN) had at least one case of ITB, whereas a control pen (CTR) had none. Individual feeding-related data including consumed feed, bout length and -frequency were collected by a single automatic ad libitum feeder. Time (week) relative to ITB onset was referred to as RELWEEK. The time before (PRE-ITB, RELWEEK -10 to 0, n=13 TBPEN and 23 CTR pens) and after ITB onset (POST-ITB, RELWEEK 0 to 4, n=9 TBPEN and 21 CTR) were analysed separately. Effects of TBPEN (vs CTR), bodyweight and RELWEEK were analysed using a linear mixed model with RELWEEK as repeated and pen as random effect.

Results: PRE-ITB the number of predicted feeder visits was lower in TBPEN as compared to CTR and decreased with age (PRED = -18 to -39% at RELWEEK -10 to 0; TBPEN effect p=0.02), leading to a tendency for a shorter daily time in the feeder (TBPEN effect p=0.06). TBPEN showed a growth dip to a -11% PRED level in RELWEEK -9 (TBPEN x RELWEEK p=0.001). Feeding behaviour changed in TBPEN in RELWEEK -2 to 0. Significant TBPEN x RELWEEK –interactions (p≤0.02) indicated that the relative decrease in the number of feeding bouts accelerated. Together with a progressive shortening of the average feeding bout this led to decreasing relative feed intake and growth (PRED= -10%, -7% and -8% at RELWEEK 0, respectively). POST-ITB TBPEN still spent less time in the feeder than CTR (TBPEN p=0.04), whereas the difference in the number of visits was decreasing (TBPEN x RELWEEK p<0.001). There was a tendency for a higher intake per second (TBPEN p=0.08) and a significantly faster RELWEEK-related increase in intake per visit (TBPEN x RELWEEK p<0.05), as well as increasingly faster growth (PRED= +9% at RELWEEK 4, TBPEN p=0.02) in TBPEN as compared to CTR. The amount of feed consumed did not differ.

Conclusion: Changes in feeding behaviour in TBPEN 10 weeks before ITB suggests presence of some tail-biting related factor. A growth dip 9 weeks before ITB may indicate the involvement of health problems in tail biting. Rapid changes in feeding behaviour suggest that tail biting behaviour begins or escalates 2 weeks before the first tail wounds are detected. TBPEN shows compensatory growth unrelated to feed intake in the month after ITB onset.

Poster Munsterhjelm IPVS

The perception of pain by pigs and implications for farm and veterinary practice

The perception of pain by pigs and implications for farm and veterinary practice. Edwards, S., 2016. Royal Dublin Society: Abstracts book of the 24th International Pig Veterinary Society (IPVS) Congress, Dublin, Republic of Ireland 7-10th June 2016. p. 13-17.

Abstract

“Freedom from pain, injury and disease” is one of the fundamental aspects of good animal welfare. However, in commercial pig production there are a number of situations where animals may experience pain. This may result from procedures carried out deliberately for management purposes, or from spontaneous health disorders. In order to make decisions on the ethical justification of procedures and the provision of pain alleviation by appropriate anaesthesia and analgesia, it is necessary to assess the intensity and duration of pain experienced by the animals. A number of behavioural, physiological and molecular methods now exist for such assessment but, since pain is a subjective experience which the individual may express in different ways, interpreting these measures can be a challenge. Better methods are required for the practical on-farm assessment of pain and the provision of analgesia when this occurs.

Paper available in the proceedings.

Traumatic neuroma development in tail docked piglets is not associated with long-term changes in spinal nociceptive processing

Traumatic neuroma development in tail docked piglets is not associated with long-term changes in spinal nociceptive processing. By Sandercock, D., S. Smith, J. Coe, P. Di Giminiani, S. Edwards, 2016. Royal Dublin Society: Abstracts book of the 24th International Pig Veterinary Society (IPVS) Congress, Dublin, Republic of Ireland 7-10th June 2016. p. 611.

Abstract

Introduction: Concerns exist over the long term consequences for tail stump pain experienced by piglets after docking, especially in relation to traumatic neuroma development in caudal nerves after docking injury. Neuroma formation may cause detrimental sensory changes in the tail due to altered axonal excitability leading to abnormal sensation or pain.

Aims: To characterize pig tail histopathology at time intervals up to 16 weeks after tail docking and to measure expression of key neuropeptides in caudal dorsal root ganglia and spinal cord neurons associated with (i) peripheral nerve regeneration; activating transcription factor-3 (ATF3), (ii) inflammatory pain; Calcitonin gene-related peptide (CGRP) and (iii) the maintenance of chronic pain; N-methyl D-aspartate (NMDA) ionotropic glutamate receptor subtype 2B (GRIN2B) at the same time points after tail docking injury.

Materials and Methods: Thirty-two female piglets (Landrace/Large White x synthetic sireline) were used (16 docked/16 sham-docked). Piglets were tail docked (amputation of approx. 2/3 of the tail) on post-natal day 3 using a gas hot docking iron. Equivalent sham-docked piglets served as intact controls. Pigs were euthanized by barbiturate overdose 1, 4, 8 and 16 weeks after sham/tail docking. Tail stumps (2 cm) were collected post-mortem for histopathological assessment. Caudal dorsal root ganglia (Ca1-Ca4+) and associated spinal cord were collected for gene expression analysis by real-time quantitative PCR of mRNA.

Results: Non-specific epidermal and dermal changes associated with healing were observed after tail docking. Mild inflammation, ulceration and oedema were present at 1 week. Traumatic neuroma development was a consistent feature from 4 weeks after tail docking. Neuroma axonal dispersion in the tail stump was on-going 16 weeks after tail docking. ATF-3 mRNA was significantly upregulated in caudal DRGs up to 8 weeks after tail docking, but did not differ at 16 weeks compared with sham controls. Both CGRP and GRIN2B mRNA expression was significantly upregulated 1 week after tail docking in caudal spinal cord neurons but were not significantly different from sham-docked pigs thereafter.

Conclusion: Histopathological lesions that occur shortly after tail docking (beyond 1 week) are not likely to induce or maintain pain. The effects of tail docking on peripheral nerve axonal proliferation and dispersion are relatively short-lived and, although still present, are attenuated by 16 weeks after tail docking injury. Changes in peripheral and spinal nociceptive processing associated with possible inflammatory and chronic pain appear to resolve by 4 weeks after tail docking injury.

Poster Sandercock IPVS

Temporal changes in mechanical nociceptive thresholds in juvenile pigs subjected to surgical tail amputation: a model of injury induced by tail biting

Temporal changes in mechanical nociceptive thresholds in juvenile pigs subjected to surgical tail amputation: a model of injury induced by tail biting. By Di Giminiani, P., E. Malcolm, M. Leach, M. Herskin, D. Sandercock, S. Edwards, 2016. Royal Dublin Society: Abstracts book of the 24th International Pig Veterinary Society (IPVS) Congress, Dublin, Republic of Ireland 7-10th June 2016. p. 649.

Abstract

Introduction: Tail biting is a global welfare problem in the pig industry leading to significant tail injury and potential carcass rejection. The temporal effects of such injuries and subsequent healing are presently unknown, although limb amputation in humans can lead to abnormal neural activity and decreased nociceptive thresholds. In order to evaluate potential sensitisation following tail damage, we created a model by surgical amputation of tails, and assessed mechanical nociceptive thresholds.

Materials and Methods: Surgical tail resection was performed to assess the influence of age, extent of tail amputated and time since amputation on thresholds of mechanical nociception. To evaluate the effect of age at the time of injury, female pigs underwent surgery at 9 weeks (±3 days ‘weaner’) (n=19) or 17 weeks (±3 days ‘finisher’) (n=43). The effect of time after amputation was evaluated on 24 pigs at 8 weeks, and 38 pigs at 16 weeks after surgery. The effect of the extent of tail amputated was assessed by assigning the pigs to 3 treatments (‘Intact’: sham-amputation; ‘short tail’: 2/3 of tail removed; ‘long tail’: 1/3 of tail removed). A Pressure Application Measurement device was used to record mechanical nociceptive thresholds (tail flick or tail clamp withdrawal responses). Within a single session, three stimuli were applied to a skin area proximal to the site of amputation, 3 days pre-surgery, 1 week and either 8 or 16 weeks post-amputation.

Results: Across the two amputation ages, results indicated that tail amputation induced a significant reduction (P<0.05) in mechanical nociceptive thresholds in short and long tails one week after surgery. The same treatment effect was observed at 16 weeks after amputation performed at 9 weeks of age (P<0.05). For surgeries performed at 17 weeks of age, thresholds tended to be lower in short compared to intact tails (P=0.081) and significantly lower (P<0.05) in long tail pigs 8 weeks after amputation. No significant difference was observed at 16 weeks following surgeries performed at 17 weeks of age.

Conclusion: These results show that surgical amputation of pig tails leads to decreased cutaneous mechanical nociceptive thresholds in the skin area proximal to the site of injury. Results indicated that severe tail injury occurring in the weaner period may be associated with sensitisation up to 16 weeks following the injury. In contrast, injuries occurring in the finishing period appeared to be associated with shorter lasting mechanical sensitisation, resolving within 16 weeks.

Poster Di Giminiani IPVS