Two restraining devices in connection to surgical castration with or without local anesthesia: effects on piglet stress

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Hokkanen et al. Porcine Health Management (2025) 11:21 Porcine Health Management https://doi.org/10.1186/s40813-025-00428-7 RESEARCH Open Access Two restraining devices in connection to surgical castration with or without local anesthesia: effects on piglet stress Ann-Helena Hokkanen1,2*, Mathilde Coutant3, Mari Heinonen1,2, Marianna Norring1,2, Magdy Adam1,2, Claudio Oliviero1,2, Tiina Bergqvist1,2 and Anna Valros1,2 Abstract Background Surgical castration causes severe pain to young piglets. In addition, piglets experience intense stress from handling and restraining during the procedure. Furthermore, piglets must be restrained twice when receiving local anesthesia before castration, and the injections are painful. Unfortunately, strategies to reduce piglets’ stress during handling, local anesthetic injections, and painful procedures are limited and poorly understood. Thus, we randomized 179 male piglets aged 3 to 4 days to be restrained with either a commonly used commercial tubular bench with a dorsal restraining posture or a custom-made castration rack with a vertical restraining posture. Piglets received local anesthetic or sham injections (mimicking local anesthesia but without skin penetration) 10 min before castration. We then compared the effect of these devices on the piglets’ behavioral reactions, vocalizations, and body temperatures at the following four times: when restrained for the first time, when given local anesthetic injections or receiving sham injections, during the second time restrained, and during castration. Results Piglets were given higher mean reaction scores when restrained in the tubular bench than the castration rack. Piglets showed differing vocalization patterns in the two devices, with more grunts and screams in the castration rack

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bench than the castration rack. Piglets showed differing vocalization patterns in the two devices, with more grunts and screams in the castration rack and more squeals in the tubular bench. Moreover, local anesthetic injections resulted in higher mean reaction scores and longer vocalizations than sham injections during the injections/sham injections but reduced these measures during castration. After castration, the skin temperature was higher in sham-injected piglets than in piglets castrated with local anesthesia, irrespective of the restraining device used. Conclusions Local anesthesia reduced piglets’ reaction scores and vocalizations during castration. However, receiving local anesthesia was painful. Based on piglet behavior, restraining in a tubular bench was more aversive than in the castration rack. However, the devices affected the proportions of the different vocalization types during local anesthetic injections and castration in a manner we cannot fully explain. As the restraining method affects piglets’ behavior, it may influence pain assessment during local anesthetic injections and evaluation of local anesthesia efficacy during castration. Thus, less stressful methods to handle piglets are needed. *Correspondence: Ann-Helena Hokkanen ann-helena.hokkanen@helsinki.fi Full list of author information is available at the end of the article © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material

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author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit ​h​t​t​p​​:​/​/​​c​r​e​a​​t​i​​v​e​c​​o​m​m​​o​n​s​.​​o​r​​g​/​l​i​c​e​n​s​e​s​/​b​y​/​4​.​0​/. The Creative Commons Public Domain Dedication waiver (​h​t​t​p​​:​/​/​​c​r​e​a​​t​i​​v​e​c​​o​m​m​​o​n​s​.​​o​r​​g​/​p​​u​b​l​​i​c​d​o​​m​a​​i​n​/​z​e​r​o​/​1​.​0​/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Hokkanen et al. Porcine Health Management (2025) 11:21 Page 2 of 14 Keywords Piglets, Handling, Castration bench, Procaine with epinephrine, Castration, Pain, Behavioral reactions, Animal welfare, Sus scrofa, Management Background restrained by an additional person or a restraining device During surgical castration, piglets < 7 days of age are con- when local anesthesia is administered to allow the use fined by holding or attaching them to a bench. Two paral- of both hands for the procedure itself. According to the lel incisions to the skin over the testicles are performed authors’ observations, piglets are calmer when restrained with a

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e itself. According to the lel incisions to the skin over the testicles are performed authors’ observations, piglets are calmer when restrained with a scalpel, both testicles are extracted from the scro- in the lap than when using a restraining device, but this, tum, and the spermatic cords are severed [1]. Despite the of course, increases labor costs. A tubular restraining brevity of the procedure, it causes considerable stress device is commonly used, where the piglets are restrained [2–4], extensive tissue damage [5, 6], and severe pain in a dorsal position. Based on the authors’ experience, both during [7, 8] and after the surgery [9, 10]. When pig- this method causes a very strong reaction in piglets. In lets are castrated without any pain alleviation, they will addition to this being a sign of potentially intense stress scream, try to escape the procedure, and swing their legs in the piglets, behavioral reactions due to handling stress vigorously [11]. Pain experienced early in life may have may compromise the evaluation of pain needed to assess many long-lasting adverse effects on pig welfare [12, 13] the efficacy of local anesthesia and other pain-mitigating and should, therefore, be reduced to minimum. strategies applied at castration. Moreover, the tubular Although the need for alternatives to surgical castra- restraining device is difficult to clean between litters and tion is widely acknowledged, implementing these meth- time-consuming to use. There is thus a need to develop ods takes time. Accordingly, effective pain alleviation and evaluate alternative restraining methods for pig- during castration is needed [14, 15]. Currently, in Fin- lets. One possible alternative to the tubular restraining land, qualified persons are allowed to castrate male

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is needed [14, 15]. Currently, in Fin- lets. One possible alternative to the tubular restraining land, qualified persons are allowed to castrate male pig- device is a custom-made castration rack, where the pig- lets < 7 days of age with an open surgical method without lets are restrained in a vertical position and hung from tearing the tissues. Before castration, piglets must receive their groins with their heads down while held in place by a non-steroidal anti-inflammatory drug (NSAID). Since the handler’s body. The practical benefit of this device is January 2024, people who have completed training and that it poses fewer hygiene challenges and is perceived as passed the qualification test are allowed to apply local easier and faster to use than a tubular restraining device. anesthesia to the piglets before castration. By 2027, the However, in both devices, the piglets are restrained in use of local anesthesia before castration will be manda- unnatural postures. tory [16]. However, while using pain alleviation with an The primary objective of this study was to compare NSAID and a local anesthetic will reduce piglets’ reac- the effect of two different restraining devices, a com- tions to castration, they seldom eliminate pain entirely mercially available tubular castration bench (TUBE) and during or after castration [3, 4, 10, 17, 18]. a custom-made castration rack (HANGING), on piglets’ In addition to castration pain, piglets experience stress during handling, administration of local anesthe- intense stress from handling and restraining during the sia, and surgical castration. The secondary aim was to procedure [19]. Furthermore, piglets must be restrained assess whether the restraining device affects the clarity of twice when they receive local anesthesia

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re [19]. Furthermore, piglets must be restrained assess whether the restraining device affects the clarity of twice when they receive local anesthesia before castra- behavioral differences between piglets during the admin- tion. First, the piglets are handled for NSAID administra- istration of local anesthesia versus sham injections and tion and injecting local anesthesia. Then, a waiting period between piglets castrated with or without local anesthe- of 5 to 30 min is needed for the local anesthetic agent to sia. To that extent, we evaluated the animals’ behavioral take effect [20]. The piglets are then handled again for reactions, vocalizations, and skin temperature. More- castration. over, we studied the time required to restrain piglets, to Piglet behavioral reactions and vocalizations have administer local anesthesia, and to castrate the piglets in been previously studied in connection to stress and pain these devices. caused by local anesthetic injections and castration [2, 3, 11, 19, 21, 22]. Moreover, skin temperature changes can Methods indicate stress and pain [11, 23–25]. However, to our The University of Helsinki Viikki Campus Research Eth- knowledge, there are no studies on how piglets should ics Committee (17/2023) approved the study protocol. be held during the administration of local anesthesia to Written consent from the animal owners was obtained. minimize stress. Only one study has explored how piglets perceive different restraining devices during castration Animals and housing itself [22]. One person can perform castration without We conducted the study in the farrowing unit of a com- a restraining device. However, the piglet needs to be mercial piglet-producing farm in Southern Finland. The Hokkanen et al. Porcine Health Management (2025) 11:21

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device. However, the piglet needs to be mercial piglet-producing farm in Southern Finland. The Hokkanen et al. Porcine Health Management (2025) 11:21 Page 3 of 14 experiment day was a farm’s routine castration day in Study design October 2023. In total, we included 179 male crossbred Timeline piglets (Yorkshire & Finnish Landrace x Tempo) from 23 The study timeline is presented in Fig. 1. An experienced litters. farm employee (later referred to as the handler) per- The average parity of the sows was 3.4 (range 1–5), formed piglet handling and castration. Initially, the han- including one litter from a primiparous sow. The sows dler carefully collected all the piglets and placed them were fed daily 4 kg of a mixed ration (a farm-made feed in the piglet nest. Subsequently, she lifted one piglet at mixture with energy 8.8 MJ, crude protein 150.7 g/ a time from the nest and injected a suspension of 45 mg kg, and crude fiber 57.9 g/kg). Water was available ad toltrazuril (coccidiostat) and 200 mg gleptoferron (iron) libitum. (Forceris™, 1.5 mL, Ceva Animal Health A/S, Libourne, All piglets were born during the same week and housed France) intramuscularly and returned the female pig- in similar conditions in two different farrowing rooms, lets to the sow. She turned male piglets towards one of each housing 45 sows in pens (3 m x 2.5 m) with partly the researchers, who measured skin temperature and slatted flooring. Sows were loose housed but confined marked the piglet in numerical order with a text marker. in crates during the first days after farrowing. The crates Then, the handler put the male piglets back in the nest. were opened after piglet castration. The room tempera- From the nest, the handler picked piglets one by one ture in the farrowing unit was 21.5 °C.

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t. were opened after piglet castration. The room tempera- From the nest, the handler picked piglets one by one ture in the farrowing unit was 21.5 °C. The piglet nest unaware of the predetermined treatment order used to had a solid concrete floor bedded with sawdust and a ensure all treatments were performed within each litter floor temperature of 38 °C. On the day of the study, the and to achieve a similar number of piglets within each age of the piglets was 3 days in 22 litters and 4 days in treatment. one litter. Piglets were not ear tagged or marked, not tail When all male piglets from the given litter were in the docked, and their teeth were left intact. As the study was nest, the handler lifted the first male piglet (in numeri- performed in connection with the normal farm routines, cal order) and fixed it into the restraining device (either we were unable to weigh the piglets. However, we divided TUBE or HANGING according to the predetermined the piglets into two size groups (normal and small) after order, described in more detail below under the heading visually estimating their size, thus simulating how it procedures). Then, the handler fixed the piglet in place would be done in practice on a pig farm. We included and while a veterinarian approached the piglet and secured it randomly allocated to the different groups only piglets in in place in the device using his hands (TUBE) or his body sound general condition with completely descended tes- (HANGING). At this stage, the two observers scored the ticles and free of overt anatomical malformations. reaction of the piglet (timepoint RESTRAIN 1). Then, the Fig. 1 Timeline of the study investigating restraining devices and the use of local anesthesia in piglet castration. An injection containing iron and coc-

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1 Timeline of the study investigating restraining devices and the use of local anesthesia in piglet castration. An injection containing iron and coc- cidiostat and an injection of meloxicam were administered to all study piglets. The piglets were restrained at two time points (RESTRAIN 1 and RESTRAIN 2) using either a tubular castration bench (TUBE) or a castration rack (HANGING). The piglets received either local anesthesia (LA) or sham injections (NO LA) at the timepoint LOCAL. Finally, surgical castration was performed at the timepoint CASTRATION. Between all procedures, the piglets stayed in their nests Hokkanen et al. Porcine Health Management (2025) 11:21 Page 4 of 14 veterinarian administered either local anesthesia (LA) piglet. We then performed the same procedures for the or sham injections (NO LA), and the observers scored other piglets of the litter in numerical order. the reaction to LA or NO LA (timepoint LOCAL). Sub- sequently, the handler took the piglet out of the device, Procedures injected the NSAID meloxicam (Metacam® 5 mg/mL, Handling and restraining devices: We randomized the injection solution for cattle and swine, Boehringer Ingel- piglets to be handled with either a commercially available heim Pharma GmbH & Co. KG, Ingelheim am Rhein, tubular castration bench (TUBE, Fig. 2a) or a custom- Germany; target dose approximately 0.4 mg/kg body made castration rack (HANGING, Fig. 2b). In TUBE, weight intramuscularly according to farm routine prac- piglets were restrained in a dorsal position in a narrow tice), turned the piglets towards the researcher for skin tubular part, with their hind legs pushed cranially by a temperature measurement, and then returned the piglet metal bar. In HANGING, the piglets were restrained in a to the nest. We handled all

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anially by a temperature measurement, and then returned the piglet metal bar. In HANGING, the piglets were restrained in a to the nest. We handled all male piglets in the litter the vertical position as they were hung from their groins with same way, and video and audio recorded all procedures their heads down while held in place by the handler’s using an iPhone 11 pro, video HD (1080 pixels) 30 frames body. per second. After all male piglets in the litter had been handled, Local anesthesia (LA) We randomized half of the TUBE- there was a 10-minute interval between LA administra- handled piglets and half of the HANGING-handled piglets tion for the first piglet and starting castration, during to receive either LA or NO LA. We used a solution con- which time we performed the same procedures described taining 40 mg/mL procaine hydrochloride and 0.036 mg/ above for the next litter. mL epinephrine tartrate (Procamidor Comp® Vet., 40 mg/ After the 10-minute waiting period, the handler took mL, Richter Pharma AG, Wels, Austria), administered the first piglet (in numerical order starting at number the product using an automatic self-filling syringe (HSW one, i.e., the piglet that received LA first) from the nest, ECO-MATIC®, Henke-Sass, Wolf GmbH, Tuttlingen, turned it to the researcher for skin temperature measure- Germany) with a 27 G needle (0.4 × 13 mm) and replaced ment, and then put the piglet in the restraining device needles between each litter. For normal-sized piglets, a according to its assigned treatment (TUBE or HANG- total of 1.5 mL of the anesthetic solution (equivalent to ING). The observers scored the reaction of the piglet 60 mg of procaine) was administered across three sepa- (timepoint RESTRAIN 2). Then, the handler surgically rate injection sites,

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action of the piglet 60 mg of procaine) was administered across three sepa- (timepoint RESTRAIN 2). Then, the handler surgically rate injection sites, with each site receiving 0.5 mL. For castrated the piglet, and the observers scored the reac- small piglets, the dosage was reduced to 0.9 mL in total tion of the piglet to castration (timepoint CASTRA- (equivalent to 36 mg of procaine), divided into three injec- TION). Then, the handler took the piglet from the device, tions of 0.3 mL each. The same veterinarian performed turned it towards the researcher for skin temperature all local anesthetic injections. First, he fixed the testicles measurement, and carefully put it back in the pen with caudally between the thumb and middle finger, applying the sow. At this point, the study ended for this individual a steady but low pressure during the fixation (see Fig. 3). Fig. 2 Piglet restraining devices used in the study. Piglets were restrained either with a tubular castration bench (Fig. 2a) or with a castration rack (Fig. 2b). In Fig. 2a, the piglet is being given a sham injection, while in Fig. 2b, the piglet receives subcutaneous local anesthesia Hokkanen et al. Porcine Health Management (2025) 11:21 Page 5 of 14 Fig. 3 The three-step method of injecting the local anesthetic agent for castration. After securing the testicles with his fingers, the veterinarian inserted the needle subcutaneously on the right testicle, injected the anesthetic agent continuously while withdrawing the needle, released the testicle, and repeated the procedure for the left testis. Lastly, he inserted the needle to its full length (13 mm) between the two testicles, aiming at the area around the spermatic cords, and injected the third dose of the local anesthetic Then, he inserted the needle just

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he two testicles, aiming at the area around the spermatic cords, and injected the third dose of the local anesthetic Then, he inserted the needle just beneath the skin of the following four time points: when the piglet was restrained scrotum (Cutis scroti) of the right testicle and injected for the first time (RESTRAIN 1), during local anesthetic the anesthetic agent subcutaneously by continuously dis- injections or sham injections (LOCAL), during the sec- pensing the drug while withdrawing the needle and then ond time the piglet was confined (RESTRAIN 2), and releasing the testicle. The veterinarian repeated the same during castration (CASTRATION). Three observers are procedure under the scrotal skin of the left testis. He then recommended for such subjective scorings [26]. How- inserted the needle to its full length (13 mm) between ever, due to space restrictions at the farm, two observ- the two testicles, targeting the area around the spermatic ers were present during piglet handling and performed cords, and injected the third dose of the local anesthetic direct observations. The third observer assessed the agent (Fig. 3). Subsequently, the handler removed the pig- piglets’ reactions from videos recorded with an iPhone let from the restraining device and placed it into the nest. placed approximately 20–30 cm from the piglets’ heads. All observers could see with which device the piglet was Sham injections (NO LA) The handler secured the pig- handled and, for many of the animals, also whether the lets in the restraining devices as described above. The piglet was receiving LA or NO LA. However, the three veterinarian then fixed the testicles with his fingers and observers were blinded regarding whether the piglet was touched the testicles with an automatic

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rinarian then fixed the testicles with his fingers and observers were blinded regarding whether the piglet was touched the testicles with an automatic syringe (with a castrated with or without local anesthesia. capped needle on) at the same three locations as described in Fig. 3 to simulate LA administration but without any Vocalizations tissue damage. The handler then removed the piglet from We recorded vocalizations from the video recordings the restraining device and placed it into the nest. described above and analyzed the vocalizations during the administration of LA and NO LA (LOCAL) and dur- Castration After securing the piglet in the restraining ing castration (CASTRATION). In the tubular restrain- device, the handler used a scalpel blade to cut an incision ing device, both periods started when the handler locked (approximately 1 cm) through the scrotal skin and sper- the hind bar that fixed the piglet to the device and ended matic fasciae. She then gently pressed the right testicle when she touched the same bar to open it and take the between her index finger and thumb until it was entirely piglet out of the device after injections or castration. In outside the scrotum. She carefully lifted the testicle verti- the HANGING restraining device, the periods started cally and cut the spermatic cord a few millimeters below when the handler put the piglet’s hind limbs on the the testicle using the scalpel. She then made the second device and let go of the legs (i.e., when the piglet was held incision and repeated the procedure on the left testicle. in place with the handler’s body) and ended when she Between each piglet, she disinfected the blade in a povi- touched the pig to take it out of the device. done-iodine solution and a new blade was used after each We

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piglet, she disinfected the blade in a povi- touched the pig to take it out of the device. done-iodine solution and a new blade was used after each We analyzed the vocalizations with Raven Pro 1.6 bio- litter. acoustics analysis software (Cornell Lab of Ornithology, Ithaca, New York, USA). We manually selected each Data collection vocalization in the audio files to obtain its duration and Behavioral reactions categorized it as a grunt, scream, or squeal according to Three observers independently scored piglets’ behavioral previously reported method [19]. A grunt was character- reactions (including piglet movements, such as kicking ized as a vocalization with a low tone, a scream as a vocal- and struggling, and vocalizations) on a scale from 0 (no ization with high, long and loud tone (often as long as an reaction) to 10 (the worst reaction imaginable) at the expiration of the piglet), and a squeal was a vocalization Hokkanen et al. Porcine Health Management (2025) 11:21 Page 6 of 14 with high tone (could be with different notes) [19]. We in her hands and ended when the piglet’s legs were posi- then calculated the mean call durations of all calls and tioned correctly in the device, and she could let go. The separately for each call type during LOCAL and CAS- procedural duration (LOCAL or CASTRATION) started TRATION in seconds. As the durations of different pro- when the handler locked the hind bar to its final position cedures (administering local anesthesia, administering (TUBE) or let go of the piglet’s legs (HANGING) and sham injections, and castration) were different, we calcu- ended when she touched the piglet for the first time to lated the duration (seconds) of vocalizations per second take it out of the device. of the procedure during LOCAL and CASTRATION

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for the first time to lated the duration (seconds) of vocalizations per second take it out of the device. of the procedure during LOCAL and CASTRATION by dividing the sum of call durations by the duration of the Statistical analysis procedure (obtained from the video recordings). We used IBM SPSS Statistics version 29.0 (IBM Inc. Chi- cago, IL) to analyze the data. Skin temperature We used an interclass correlation analysis with a two- We used a hand-held infrared thermometer (model PCE- way mixed effect model assuming consistency to assess IR 100; PCE Produktions und Entwicklungsgesellschaft the consistency of reaction scoring between the observ- mbH, Meschede, Germany) to measure changes in skin ers. The overall inter-observer reliability was excellent temperature [25]. We measured skin temperature near during all four observation periods (Interclass correla- the internal organs, ventrally at the base of the ster- tion [df = 343–357]: 0.92–0.95, 95% confidence interval: num near the xiphoid process (Fig. 4) after RESTRAIN 0.90–94 [lower bound] − 0.93–0.96 [upper bound]). Thus, 1 + LOCAL and RESTRAIN 2 + CASTRATION. Skin we used the mean score of the observations in the sta- temperature was also measured before these procedures tistical analysis (mean reaction score). Continuous vari- to allow us to control individual differences (see also ables were assessed for normality visually and using the timeline, Fig. 1). Shapiro-Wilk test. Mean reaction scores and duration of vocalizations Time needed to restrain piglets and duration of procedures during the four different time points (RESTRAIN 1, We analyzed video recordings to determine the time LOCAL, RESTRAIN 2, CASTRATION), and skin tem- required for restraining the piglets (restraining duration) perature

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eo recordings to determine the time LOCAL, RESTRAIN 2, CASTRATION), and skin tem- required for restraining the piglets (restraining duration) perature after the procedures (LOCAL and CASTRA- and performing the procedures (administration of local TION) were all normally distributed. Accordingly, we anesthesia, sham injections, and castration) (procedural studied the effects of the restraining device and local duration) in the TUBE or HANGING device. For the anesthesia on piglets’ mean reaction scores and vocaliza- TUBE, the restraining duration started from the moment tions during each of the different time points, and skin the handler turned the piglet onto its back (still in the temperature after the procedures, using separate mixed hands of the handler) and ended when the handler locked models. The models included restraining device (TUBE the hind bar of the device in the final position. For the or HANGING), treatment (local anesthesia [LA] or HANGING device, the restraining duration started from sham injections [NO LA]), piglet size (small or normal, the moment the handler turned the piglet’s head down based on visual estimation), and the interaction between Fig. 4 Location of the skin temperature measurement. Skin temperature was measured ventrally at the base of the sternum near the xiphoid process with a hand-held infrared thermometer Hokkanen et al. Porcine Health Management (2025) 11:21 Page 7 of 14 Table 1 Number of study piglets (n = 179) according to their size We estimated the sample size based on previous and treatment group research [3]. Due to technical and human errors, some Treatment group Piglet size Total data were missing (n = 172–179 for behavioral reactions normal small and vocalizations, and n = 162–176 for skin temperature Local

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p Piglet size Total data were missing (n = 172–179 for behavioral reactions normal small and vocalizations, and n = 162–176 for skin temperature Local anesthesia in tubular device 30 19 49 measurements), resulting in different sample sizes in dif- Sham injections in tubular device 24 20 44 ferent comparisons. P-values < 0.05 were considered sta- Local anesthesia in castration rack 28 15 43 tistically significant and p-values < 0.1 as tendencies. Sham injections in castration rack 31 12 43 Results restraining device and treatment as fixed factors, with The 179 piglets were randomized into different treatment sow included as a random factor. However, sow as a groups (LA in TUBE, NO LA in TUBE, LA in HANG- random factor was redundant in the model for grunts ING, and NO LA in HANGING), as shown in Table 1. during castration. For temperature after LOCAL and Table 1 also shows the number of piglets per treatment CASTRATION, skin temperature before the procedure according to their size (normal or small). was included as a covariate. The results are presented as estimated means (EM) and standard errors (SE). In lin- Behavioral reaction scores ear mixed-effects models, deviations from assumption of Both the restraining device and the LA vs. NO LA treat- normality and variance homogeneity were assessed with ment influenced the mean reaction scores of the pig- Kolmogorov-Smirnov test and visually by examining the lets. As expected, only the device affected the mean residual plots. reactions during the time points, including handling We studied the time needed to restrain piglets and the only (RESTRAIN 1 and RESTRAIN 2, see Fig. 5a and duration of different procedures (administration of local c). The reaction of the piglets was scored to be higher anesthesia/sham injections

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g. 5a and duration of different procedures (administration of local c). The reaction of the piglets was scored to be higher anesthesia/sham injections and castration) in the differ- in the TUBE than in the HANGING treatment at both ent treatment groups with pairwise comparisons per- time points. During LOCAL, the reaction of the piglets formed with t-tests. The results are presented as mean was scored to be higher both in the TUBE as compared and standard deviations (SD). to the HANGING device and in the piglets given LA as Fig. 5 Estimated marginal mean and standard error for mean reaction scores for piglets restrained with different devices and treated with or without local anesthesia. The piglets were restrained either with a tubular device (TUBE) or a castration rack (HANGING). The piglets received either local anesthesia (LA) or sham injections (NO LA) before castration. Three observers scored piglets’ reaction at four time points: (a) RESTRAIN 1 (only restraining, n = 172); (b) LOCAL (restraining and administration of local anesthesia/sham injections, n = 177); (c) RESTRAIN 2 (only restraining, n = 178) and (d) CASTRATION (restraining and surgical castration, n = 179) Hokkanen et al. Porcine Health Management (2025) 11:21 Page 8 of 14 compared to NO LA (Fig. 5b). During CASTRATION, than normal-sized piglets (for full model results, see Sup- the restraining device did not influence the reaction plementary Tables 2a-e and 3a-e). score, but piglets in the NO LA group were scored to The proportions of different types of vocalizations react stronger than those in the LA group (Fig. 5d). The (mean durations per second) of piglets in the different interaction between restraining devices and LA vs. NO treatment groups during LOCAL and CASTRATION are LA was not

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second) of piglets in the different interaction between restraining devices and LA vs. NO treatment groups during LOCAL and CASTRATION are LA was not significant in any of the models. Small pig- shown in Fig. 8a and b, respectively. A relatively higher lets got lower mean reaction scores during all time points proportion of vocalizations were screams during CAS- compared to normal size piglets (for full model results, TRATION in the piglets that had not received local anes- see Supplementary Tables 1a-e). thesia (Fig. 8b). Proportions of grunts and screams were higher in the group restrained in the HANGING device Vocalizations as compared to the TUBE device, while squeals occurred Differences in piglets’ vocalizations between the two at a higher proportion in the TUBE than in the HANG- devices studied and between LA and NO LA are shown ING handled piglets. in Fig. 6a-d during LOCAL and in Fig. 7a-d during CAS- TRATION. Overall, piglets that received LA vocalized Skin temperature longer during the administration of local anesthesia Overall, the skin temperature of the piglets was, on aver- (Fig. 6a) and less during castration than piglets in NO age, 38.9 °C (SD 0.42 °C) before LOCAL and 38.6 °C LA (Fig. 7a). Moreover, the vocal responses of the pig- (0.48 °C) before CASTRATION, and 38.9 °C (0.36 °C) vs. lets during the administration of the local anesthetic 38.6 °C (0.49 °C) after LOCAL and after CASTRATION (Fig. 6b and d) and castration (Fig. 7b-d) were affected respectively. The skin temperature did not differ between by the restraining device used. The interaction between the treatment groups after LOCAL, even though it was restraining devices and LA vs. NO LA was not signifi- numerically higher in the TUBE and LA groups than in cant in any of the models.

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en though it was restraining devices and LA vs. NO LA was not signifi- numerically higher in the TUBE and LA groups than in cant in any of the models. There was no difference in the other treatment groups (Fig. 9a). After CASTRATION, total duration of vocalizations during either LOCAL or the skin temperature tended to be higher in NO LA CASTRATION between small and normal-sized piglets. piglets than in LA piglets (p = 0.05), irrespective of the However, small piglets grunted longer and screamed less restraining device used (Fig. 9b). The interaction between Fig. 6 Estimated marginal mean and standard error for the duration (seconds) of piglets’ vocalizations per second during the administration of local anesthesia (LA) or sham injections (NO LA). Different vocalizations of piglets are presented as total vocalizations (a, n = 178), grunts (b, n = 178), screams (c, n = 178), and squeals (d, n = 178). Piglets had been treated with local anesthesia (LA) or sham injections (NO LA), and they were restrained either with a tubular bench (TUBE) or a castration rack (HANGING) Hokkanen et al. Porcine Health Management (2025) 11:21 Page 9 of 14 Fig. 7 Estimated marginal mean and standard error for duration (seconds) of piglets’ vocalizations per second during castration. Different vocalizations of piglets are presented as total vocalizations (a, n = 179), grunts (b, n = 179), screams (c, n = 179), and squeals (d, n = 179). Piglets had been treated with local anesthesia (LA) or sham injections (NO LA) and they were restrained either with a tubular bench (TUBE) or a castration rack (HANGING) Fig. 8 Proportions of different piglet vocalizations of all vocalizations recorded during the procedures. Results are shown for each treatment group sepa- rately: the piglets were either

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et vocalizations of all vocalizations recorded during the procedures. Results are shown for each treatment group sepa- rately: the piglets were either restrained in a tubular device (TUBE) or a hanging castration rack (HANGING), and treated with local anesthesia (LA) or with sham injections (NO LA) during administration of local anesthesia or sham injections (LOCAL) (a) and during castration (CASTRATION) (b) the restraining device and LA vs. NO LA was not signifi- Durations required for each procedure cant in either of the models. The piglet size category did The restraining duration was shorter with HANG- not influence skin temperature, but temperature before ING than TUBE (3.5 ± 2.0 versus 6.3 ± 3.2 s, p = 0.001). correlated positively with the temperature after both Moreover, administering LA took 14.9 ± 6.1 s, NO LA LOCAL and CASTRATION (for full model results, see 9.3 ± 1.6 s, and castration 14.2 ± 4.7 s. Administering LA Supplementary Tables 4a and b). lasted 11.7 ± 5 s in TUBE and 12.6 ± 5.4 s in HANGING (p = 0.928). Castration required 14.3 ± 4.5 s in TUBE and 14.1 ± 4.9 s in HANGING (p = 0.843). Castration after Hokkanen et al. Porcine Health Management (2025) 11:21 Page 10 of 14 Fig. 9 Estimated marginal mean and standard error for skin temperature of piglets measured with an infra-red thermometer near the xiphoid process. Results are shown after the first restraining and administration of local anesthesia (LA) or sham injections (NO LA) (a, n = 162) and after the second restrain- ing and castration with local anesthesia (LA) or sham injections (NO LA) (b, n = 176). The piglets were restrained with either a tubular bench (TUBE) or a castration rack (HANGING) LA took less time (13.3 ± 3.1 s) compared to after NO LA the sham injections (NO LA).

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ith either a tubular bench (TUBE) or a castration rack (HANGING) LA took less time (13.3 ± 3.1 s) compared to after NO LA the sham injections (NO LA). Moreover, NO LA piglets (15.2 ± 5.8 s) (p < 0.001). had higher reaction scores during castration than LA piglets. Our findings are consistent with the literature, as Discussion several authors concluded that local anesthesia induces We found that the restraining device affected the piglets’ stress, discomfort, and pain [3, 4, 27], and piglets treated behavioral reaction scores during handling and piglets’ with local anesthesia prior to castration resisted less dur- vocalizations both during local anesthetic administration ing the procedure than their counterparts castrated with- and castration. Piglets received higher reaction scores out local anesthesia [2, 11, 28]. when restrained with TUBE than with HANGING. Thus, Interpreting the results becomes more complex when they possibly perceived TUBE as more aversive than vocalizations are considered; piglets tended to vocalize HANGING. The validity of our reaction scoring method longer when castrated in HANGING than in TUBE. This is supported by the piglets’ stronger behavioral reaction contradicts our finding that piglets had higher behavioral scores during local anesthetic administration (LA) than scores when restrained in TUBE. Indeed, piglets also Hokkanen et al. Porcine Health Management (2025) 11:21 Page 11 of 14 vocalized longer when receiving LA than NO LA and different proportions of vocalizations during painful pro- when castrated after NO LA than LA. These findings are cedures. During LOCAL, the proportion of screams was consistent with other studies [3, 4, 29, 30]. For example, greater among LA piglets than among NO LA piglets in Coutant et al. [3] found

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f screams was consistent with other studies [3, 4, 29, 30]. For example, greater among LA piglets than among NO LA piglets in Coutant et al. [3] found that the local anesthetic injec- TUBE but not in HANGING. In contrast, the propor- tions resulted in higher values of vocal parameters than tion of grunts remained similar in both devices, while those of sham-handled piglets, indicating a significant the proportion of squeals was slightly greater among stress response [31]. Moreover, Lou et al. [30] observed NO LA than among LA piglets in TUBE but again not in that piglets castrated under 24 h of age produced more HANGING. In contrast, the vocalization pattern shifted vocalizations of a higher frequency than sham-castrated noticeably during castration; the proportion of grunts piglets, and these high-frequency vocalizations tended to was much lower, and the proportions of screams and be longer in duration during castration than during sham squeals were much greater among NO LA than LA. The castration. In contrast to our findings, Weary and col- proportion of screams was especially high when piglets leagues [21] found no effect of the handling method on were restrained in the vertical position during castra- the rate of high calls produced by the piglets in connec- tion. Thus, grunting could be more a sign of overall dis- tion to castration. Piglets suspended by their rear legs in comfort (and maybe also a piglet’s effort to contact the the handler’s hands had low calls at a slower rate than pig- mother sow) and is replaced by squealing and screaming, lets restrained in a bench in a dorsal position. Moreover, calls previously found to be used by piglets experiencing piglets restrained dorsally on the bench produced low severe pain and distress [11, 21, 22, 32], during

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ously found to be used by piglets experiencing piglets restrained dorsally on the bench produced low severe pain and distress [11, 21, 22, 32], during castration. calls at a lower rate than those restrained in a V-trough We wanted to study piglets’ reactions and vocalizations [21]. Thus, evaluating different restraining methods by in a real-life setting in a commercial piggery with as few their aversiveness needs further research. It is possible deviations from normal procedures as possible. Natu- that longer vocalizations produced while castrated with rally, this approach limited our ability to record more HANGING when compared with TUBE may result from advanced vocal parameters. There are limitations in using different body postures during restraining; piglets could durations and categories of vocalizations to measure pain probably vocalize longer while hanging upside down than and stress in young piglets. Indeed, previous studies have when restrained in the dorsal position with the hind legs shown that more advanced vocal parameters, such as pushed cranially. Additionally, it is also possible that the frequency, energy, or amplitude, seem to be more sensi- two different restraining postures were perceived as dif- tive and accurate in reporting pain and stress than other ferentially aversive. Being restrained dorsally in a narrow general measures, such as average call duration or pro- TUBE and having legs fixated on the bench may provoke portion of call time used in the current study [19]. Thus, more resistance behavior as an attempt to escape and future work could focus on these more complex indica- adjust body postures. However, being hung upside down tors of pain and distress. Moreover, future studies are could induce more fear of falling, thus resulting in

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postures. However, being hung upside down tors of pain and distress. Moreover, future studies are could induce more fear of falling, thus resulting in fewer needed to understand how the physical situation restricts resistance movements but more and longer high-tone piglets’ ability to express their emotions and experiences vocalizations, such as screams, which are often associ- with different types of vocalizations. Finally, our results ated with fear, panic, and pain [22]. indicate that the size of the piglet affects their vocaliza- The restraining device, administration of local anes- tions and should be considered with more care in future thetic, and castration all affected the durations and studies. proportions of different vocalizations in piglets. Dur- We chose to use vocalization variables standardized ing LOCAL, the total duration of all vocalizations was for time (i.e., duration per second), as the different time significantly longer in LA than in NO LA. Furthermore, points during the experiment differed in duration within although the restraining device did not influence the and between treatments. Thus, the outcome reflects the duration of all vocalizations during LOCAL, the pig- intensity of the negative effect of the procedures on the lets grunted longer when restrained with HANGING piglets. However, from a welfare perspective, it may be and squealed longer in TUBE. During castration, the even more relevant to assess the magnitude of the impact, total duration of all vocalizations was longer among NO i.e., the combination of intensity and duration [33]. For LA piglets than those castrated with LA. Moreover, the this, we could have used the total duration of vocaliza- restraining device influenced the duration of all vocaliza- tions (without standardizing

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the this, we could have used the total duration of vocaliza- restraining device influenced the duration of all vocaliza- tions (without standardizing for timepoint duration) as tions during castration, as piglets tended to vocalize for the outcome variables. To test for this, we analyzed the a longer time in HANGING than in TUBE. Specifically, results with both types of variables, while we decided the piglets’ grunts and screams were longer in HANG- only to report the intensity results here for simplicity. The ING than in TUBE, and piglets squealed longer in TUBE. results were very similar when using intensity and when Interestingly, the restraining device and the severity or using magnitude variables. As we believe the intensity type of pain experienced by piglets appear to affect the Hokkanen et al. Porcine Health Management (2025) 11:21 Page 12 of 14 results are easier to compare with other studies using the develop easy-to-use methods that minimize stress for same approach [e.g., 19], we opted only to report these. the piglets while also facilitating procedures and ensur- We expected the skin temperature would increase ing safety for the operator. Moreover, as strong reactions while resisting procedures by trying to escape, kicking, to handling could potentially hinder caregivers’ ability to and vocalizing. Moreover, as our measuring point is near accurately assess the methods used to provide local anes- the internal organs and the activation of the sympathetic thesia before castration and the efficacy of local anesthe- nervous system causes vasoconstriction and redirection sia during castration, less stressful handling methods are of blood flow to the internal organs [23], an increase in needed both in scientific research and in practice. Thus, temperature is

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andling methods are of blood flow to the internal organs [23], an increase in needed both in scientific research and in practice. Thus, temperature is expected. Indeed, the mean skin tempera- future studies are warranted on how piglets react to han- tures were higher after castration with NO LA than with dling, restraining, administration of local anesthesia, and LA. This aligns with our findings that the mean behav- castration while being held in the assistant’s lap. ioral reaction scores were greater among piglets in the The optimal technique to administer local anesthesia NO LA compared with the LA treatment group during in young piglets for castration remains unknown [1, 3, CASTRATION. We chose this method for measuring 34]. In particular, intratesticular injections, while com- skin temperature to add a non-invasive, rapid, and objec- mon, cause pain and possible tissue damage [3, 4]. To tive measurement indicative of piglets’ stress and resis- address this, we employed a modified technique designed tance movements to our study design. We acknowledge to deliver the local anesthetic as close as possible to the that our approach of using changes in skin temperature as incision sites but under the skin and deeper to the area an indicator of stress and pain differs from the approach where the spermatic cords will be cut. However, consis- in previous research. Specifically, prior research consid- tent with previous findings, LA still resulted in significant ered a decrease in skin surface temperature, measured behavioral reactions compared with NO LA [3, 4]. Thus, in the groin area following castration, as an indicator of the efficacy of local anesthesia before piglet castration in sympathetic nervous system activation and, thus, dis- improving welfare remains a

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ator of the efficacy of local anesthesia before piglet castration in sympathetic nervous system activation and, thus, dis- improving welfare remains a subject of ongoing debate. tress and pain [25]. Future research should be conducted The benefits of pain reduction during castration must be to explore how the skin temperature measured near the weighed against the stress and pain associated with its xiphoid process and other sites of the body correlates administration. Further research is needed to optimize with the actual body temperature among young piglets anesthetic protocols, refine handling techniques, and experiencing stress and pain while restrained in differ- develop alternative methods that minimize both the pro- ent postures. This would build on suggestions of previ- cedural and post-procedural pain experienced by piglets. ous studies examining castration-related pain in piglets One of our aims was to assess whether the restrain- [11] and reviews on the use of infra-red skin temperature ing device hinders the effective evaluation of the local measurement for monitoring porcine health and assess- anesthesia protocol during castration, as it is essential ing pain [1, 24]. that the operator can make a reliable assessment of the In addition to evaluating piglets’ behavioral reactions, efficacy of the local anesthesia used. Our results suggest vocalizations, and skin temperature, our results revealed that the type of restraining device used may indeed hin- that these restraining devices also differed in handling der this assessment. For instance, piglets restrained in duration. More time was needed to restrain the piglets the tubular device received almost similar mean behav- in TUBE than HANGING. However, the time needed to ioral scores both when first

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rain the piglets the tubular device received almost similar mean behav- in TUBE than HANGING. However, the time needed to ioral scores both when first restrained and during castra- administer LA was similar between the devices. There tion under local anesthesia. Notably, the mean difference were also no differences between the two handling in behavioral scores between piglets castrated with or methods in the duration of the castration procedure. It without local anesthesia was 3 points on a 0 to 10 scale, is worth noting that our operator has long experience in which is just one point more than the difference in scores castrating, but both devices were new to her as she usu- observed between the two restraining devices during the ally performs the procedure by holding piglets between initial restraint. This indicates that strong reaction to her thighs. However, our results show that castrating pig- handling can make it challenging, if not impossible, to lets with LA took less time than performing the proce- reliably assess the efficacy of local anesthesia. dure after NO LA, consistent with findings from previous research [2]. Considering the time needed to handle and Conclusion restrain piglets is essential, as shorter handling times are The choice of restraining method significantly affects pig- preferred for reasons of animal welfare and time manage- lets’ reactions and vocalizations, potentially preventing ment. Moreover, as using local anesthesia approximately an accurate assessment of local anesthesia efficacy. How- doubles the overall time needed to castrate individual ever, neither device was optimal as both induced strong piglets, the handling method should allow quick injec- reactions among the piglets. It is difficult to compare the tions. Therefore, our

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nduced strong piglets, the handling method should allow quick injec- reactions among the piglets. It is difficult to compare the tions. Therefore, our results emphasize the need to devices based on our results, especially as they seem to Hokkanen et al. Porcine Health Management (2025) 11:21 Page 13 of 14 3 Department of Animal and Veterinary Sciences, Aarhus University, Tjele, affect the types of vocalizations in a manner we cannot Denmark fully explain. Moreover, while the administration of pro- caine with epinephrine effectively alleviates pain in pig- Received: 31 October 2024 / Accepted: 19 February 2025 lets aged 3 to 4 days, it also requires additional handling and needle injections, inducing stress and pain, which is evident through stronger reactions and longer and more intense vocalizations. Besides increasing the welfare bur- References 1. Sheil M, Polkinghorne A. Optimal methods of documenting analgesic effi- den of the procedure for the piglets, the strong reactions cacy in neonatal piglets undergoing castration. Animals. 2020. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​ to handling can complicate or even prevent the assess- /​​1​0​.​​3​3​9​0​​/​a​​n​i​1​0​0​9​1​4​5​0. ment of pain and distress caused by the local anesthetic 2. Skade L, Kristensen CS, Friis Nielsen MB, et al. Effect of two methods and two anaesthetics for local anaesthesia of piglets during castration. Acta Vet Scand. injections and the effect of local anesthesia during castra- 2021. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​s​​1​3​0​2​8​-​0​2​0​-​0​0​5​6​6​-​8. tion. Therefore, our research

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hesia during castra- 2021. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​s​​1​3​0​2​8​-​0​2​0​-​0​0​5​6​6​-​8. tion. Therefore, our research underscores the importance 3. Coutant M, Malmkvist J, Kaiser M, et al. Piglets’ acute responses to local anes- of identifying the best methods for restraining young pig- thetic injection and surgical castration: effects of the injection method and interval between injection and castration. Front Vet Sci. 2022. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​ lets for local anesthesia administration and castration. 1​0​.​​3​3​8​9​​/​f​​v​e​t​s​.​2​0​2​2​.​1​0​0​9​8​5​8. 4. Coutant M, Malmkvist J, Kaiser M, et al. Piglets’ acute responses to procaine- Supplementary Information based local anesthetic injection and surgical castration: effects of two The online version contains supplementary material available at ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​ volumes of anesthetic. Front Pain Res. 2022. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​3​3​8​9​​/​f​​p​a​i​n​.​2​0​2​ g​/​​1​0​.​​1​1​8​6​​/​s​​4​0​8​1​3​-​0​2​5​-​0​0​4​2​8​-​7. 2​.​9​4​3​1​3​8. 5. Morales J, Dereu A, Manso A, et al. Surgical castration with pain relief affects the health and productive performance of pigs in the suckling period. Supplementary Material 1 Porcine Health Manag. 2017.

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on with pain relief affects the health and productive performance of pigs in the suckling period. Supplementary Material 1 Porcine Health Manag. 2017. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​s​​4​0​8​1​3​-​0​1​7​-​0​0​6​6​-​1. 6. Viscardi AV, Turner PV. Use of meloxicam or ketoprofen for piglet pain control following surgical castration. Front Vet Sci. 2018. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​3​3​8​9​​/​f​​v​e​t​s​ Acknowledgements .​2​0​1​8​.​0​0​2​9​9. We thank the owners and the farm personnel for participating in the study. 7. Yun J, Ollila A, Valros A, et al. Behavioural alterations in piglets after surgical We especially thank Nea Kettunen for her assistance and expertise throughout castration: effects of analgesia and anaesthesia. Res Vet Sci. 2019. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​ the long study day. We also thank Vilja Hukkinen for her assistance with video o​​r​g​/​​1​0​.​​1​0​1​6​​/​j​​.​r​v​s​c​.​2​0​1​9​.​0​5​.​0​0​9. recordings. 8. Robles I, Luna SPL, Trindade PHE, et al. Validation of the Unesp-Botucatu pig composite acute pain scale (UPAPS) in piglets undergoing castration. PLoS Author contributions ONE. 2023. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​3​7​1​​/​j​​o​u​r​​n​a​l​​.​p​o​n​​e​.​​0​2​8​4​2​1​8. A-H.H., M.C., M.H., M.A., C.O., T.B., and A.V. designed the study. A-H.H., M.H., M.A., 9. Hay M, Vulin A, Génin S, et al.

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.​p​o​n​​e​.​​0​2​8​4​2​1​8. A-H.H., M.C., M.H., M.A., C.O., T.B., and A.V. designed the study. A-H.H., M.H., M.A., 9. Hay M, Vulin A, Génin S, et al. Assessment of pain induced by castration in C.O., and A.V. collected the data. M.N. and T.B. assisted in preparing the data piglets: behavioral and physiological responses over the subsequent 5 days. for statistical analysis. M.C. was responsible for the analysis of vocalizations and Appl Anim Behav Sci. 2003. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​0​1​6​​/​S​​0​1​6​8​-​1​5​9​1​(​0​3​)​0​0​0​5​9​-​5. was involved in interpretation of the results. A-H.H. and A.V. performed the 10. Coutant M, Malmkvist J, Tallet C, et al. Administration of procaine-based local statistical processing of the data, interpreted the results, and prepared the first anaesthetic prior to surgical castration influences post-operative behaviours version of the manuscript. All the authors participated in writing and editing of piglets. Appl Anim Behav Sci. 2022. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​0​1​6​​/​j​​.​a​p​​p​l​a​​n​i​m​.​​2​0​​2​ the final manuscript and accepted it. 2​.​1​0​5​8​1​3. 11. Hansson M, Lundeheim N, Nyman G, et al. Effect of local anaesthesia and/ Funding or analgesia on pain responses induced by piglet castration. Acta Vet Scand. The Juliana von Wendt Foundation and Suomen Sianjalostuksen Säätiö 2011.

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or analgesia on pain responses induced by piglet castration. Acta Vet Scand. The Juliana von Wendt Foundation and Suomen Sianjalostuksen Säätiö 2011. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​1​​7​5​1​-​0​1​4​7​-​5​3​-​3​4. funded this research. A-H.H. thanks the Finnish Foundation of Veterinary 12. Williams MD, Lascelles BDX. Early neonatal Pain—A review of clinical and Research for a personal grant. experimental implications on painful conditions later in life. Front Pediatr. 2020. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​3​3​8​9​​/​f​​p​e​d​.​2​0​2​0​.​0​0​0​3​0. Data availability 13. Adcock SJ. Early life painful procedures: Long-Term consequences and impli- The datasets generated and/or analyzed during the current study are not cations for farm animal welfare. Front Anim Sci. 2021. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​3​3​8​9​​ publicly available due to being under further analysis but are available from /​f​​a​n​i​m​.​2​0​2​1​.​7​5​9​5​2​2. the corresponding author upon reasonable request. 14. Briyne ND, Berg C, Blaha T, et al. Pig castration: will the EU manage to ban pig castration by 2018? Porcine Health Manag. 2016. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​s​​4​0​ Declarations 8​1​3​-​0​1​6​-​0​0​4​6​-​x. 15. Heinonen M, Kastraatioselvitys. 2021.

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6. ​h​t​t​p​​s​:​/​​/​d​o​i​​.​o​​r​g​/​​1​0​.​​1​1​8​6​​/​s​​4​0​ Declarations 8​1​3​-​0​1​6​-​0​0​4​6​-​x. 15. Heinonen M, Kastraatioselvitys. 2021. ​h​t​t​p​​s​:​/​​/​v​a​l​​t​i​​o​n​e​​u​v​o​​s​t​o​.​​f​i​​/​d​o​​c​u​m​​e​n​t​s​​/​1​​4​ Ethics approval and consent to participate 1​0​​8​3​7​​/​1​8​5​​8​0​​2​7​/​​S​e​l​​v​i​t​y​​s​_​​S​i​k​​o​j​e​​n​_​k​a​​s​t​​r​a​a​​t​i​o​​_​2​0​2​​1​.​​p​d​f​​%​2​0​​/​f​a​d​​e​c​​6​f​1​​-​c​4​​a​2​-​5​​8​6​​ The study protocol was considered ethically acceptable by the University of b​-​1​​4​4​9​​-​8​f​b​​5​7​​8​c​6​​2​4​7​​b​/​S​e​​l​v​​i​t​y​​s​_​S​​i​k​o​j​​e​n​​_​k​a​s​t​r​a​a​t​i​o​_​2​0​2​1​.​p​d​f​?​t​=​1​6​4​3​8​8​6​5​7​8​6​ Helsinki Viikki Campus Research Ethics Committee (17/2023) and the written 1​3. Accessed 6 2024. owner consent was obtained. 16. Finlex 693. /2023. Laki eläinten hyvinvoinnista (Legislation in Finnish). 2023. ​h​t​ t​p​​s​:​/​​/​f​i​n​​l​e​​x​.​f​​i​/​f​​i​/​l​a​​k​i​​/​a​l​​k​u​p​​/​2​0​2​​3​/​​2​0​2​3​0​6​9​3. Accessed 6 2024. Consent for publication 17. Abendschön N, Senf S, Deffner P, et al. Local anesthesia in piglets undergo- Not

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