Surgical Castration of Piglets – Challenges and Alternatives – A Review

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Ann. Anim. Sci., Vol. 26 (2026) 201–210 DOI: 10.2478/aoas-2025-0044 SURGICAL CASTRATION OF PIGLETS – CHALLENGES AND ALTERNATIVES – A REVIEW Anna Zalewska♦, Martyna Batorska, Justyna Więcek, Anna Rekiel, Marcin Sońta Department of Animal Breeding and Nutrition, Institute of Animal Sciences, Warsaw University of Life Sciences, Ciszewskiego 8, 02-786 Warsaw, Poland ♦ Corresponding author: anna_zalewska1@sggw.edu.pl Abstract The European Declaration on Alternatives to Surgical Castration of Pigs stipulated that from 2012, surgical castration could only be performed using anesthetics and/or analgesics, and that it would be completely abandoned by 2018. Many Member States disagreed with the conditions set out in the Declaration. The issue of surgical castration arouses serious controversy among consumers due to their con- cerns over animal welfare and rearing conditions. According to the Council Directive 2008/120/EC of 18 December 2008 laying down the minimum standards for the protection of pigs, surgical castration can be performed without anesthesia until the seventh day of a piglet’s life. Castration is considered painful and can have many adverse health and production consequences. Alternatives to surgical castration include immunocastration or the fattening of entire male pigs. However, these methods also evoke many emotions in both consumers and pork producers. The most common concerns relate to the presence of boar taint in pork, and the appearance of aggressive and sexual behavior within herds. Despite ample literature sources from recent decades, it is difficult to definitively determine whether it is possible to completely eliminate the surgical castration of male pigs. While the use of anesthesia and/or analgesics appears to meet the welfare

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it is possible to completely eliminate the surgical castration of male pigs. While the use of anesthesia and/or analgesics appears to meet the welfare requirements for pigs, it also poses practical and economic challenges to producers. Key words: pigs, welfare, castration, immunocastration, boar taint, meat quality In many countries, pork is primarily sourced from be completely discontinued. Failing to reach an agree- fattened gilts and barrows. The fattening of entire male ment on the matter, many Member States chose not to pigs raises concerns due to the potential occurrence of sign and adhere to the conditions set out in the decla- boar taint in meat and aggression within pens. When de- ration (Lin-Schilstra and Ingeenbleek, 2021). Countries ciding which animals to select for fattening, producers that decided to use anesthesia during the surgical castra- cannot completely disregard consumer needs or the legal tion of piglets include Norway and Sweden, while the requirements applicable in different countries (Fàbrega use of analgesics has become the most common practice et al., 2010; Di Pasquale et al., 2020). Intensive animal in France, Belgium, and Germany. In turn, the fattening production, aimed at boosting production profitability, is of entire male pigs is a common practice in Spain and controversial among consumers, who pay increasing at- Portugal, whereas Ukraine, Poland, the Czech Republic, tention to animal welfare and rearing conditions. Today’s Italy, Croatia, Bulgaria, and Romania still predominantly consumers are no longer satisfied with an assurance of use surgical castration without anesthesia. Differences in good-quality meat; they want to be sure that it comes production strategies can be observed not only between from animals raised in good

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ifferences in good-quality meat; they want to be sure that it comes production strategies can be observed not only between from animals raised in good welfare conditions (Suther- countries but also within them. Belgium, Germany, Nor- land et al., 2012; Czech et al., 2022). The surgical cas- way, Romania, and Ukraine also use immunocastration tration of piglets evokes significant emotional responses as an alternative solution; however, it is a rarely chosen due to the stress and pain they experience (Mancini et method in this respect (Aluwé et al., 2020). In Norway, al., 2017). Surgical castration is regulated by the Coun- legal regulations prohibiting surgical castration without cil Directive 2008/120/EC of 18 December 2008 laying pain-relieving measures were implemented as early as in down the minimum standards for the protection of pigs. 2002. In Denmark, similar regulations were introduced In 2010, meetings were held between European repre- in 2009, and in Sweden in 2016. In recent years, Ger- sentatives from the pork production chain, resulting in many and France have followed suit, establishing bans the development of The European Declaration on Alter- on performing the procedure without anesthesia starting natives to Surgical Castration of Pigs. It stipulated that in 2021. This variation in the timing of implementing re- starting from 1 January 2012, surgical castration would spective regulations highlights the different pace at which only be performed using anesthetics and/or analgesics. European countries address this issue (Lin-Schilstra and Furthermore, from 1 January 2018, the procedure was to Ingenbleek, 2021). 202 A. Zalewska et al. Bearing the above in mind, the aim of this review arti- Bonneau and Weiler (2019), indicators of pain include cle is to

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2021). 202 A. Zalewska et al. Bearing the above in mind, the aim of this review arti- Bonneau and Weiler (2019), indicators of pain include cle is to summarize findings from the available literature increased vocalization, resistance, elevated heart rate, on alternatives to surgical castration in male pigs, as well and heightened urine levels of stress hormones. Hay et as to discuss the associated challenges, controversies, al. (2003) evaluated pain responses induced by the cas- and their impact on pig welfare and pork quality. tration procedure over five days post-operation. Piglets were randomly assigned to three groups of seven piglets Surgical castration each: three underwent castration, two underwent sham According to the Council Directive 2008/120/EC of castrations, and two were not subjected to any proce- 18 December 2008, the surgical castration of piglets may dures. The authors observed reduced interest in nursing be performed without anesthesia not later than the seventh (suckling and massaging the udder) among the castrated day of piglet’s life, and only by a veterinarian or a trained piglets for the first 2.5 hours post-procedure. The castrat- and experienced person using appropriate methods and ed piglets moved around the pen much more compared maintaining hygiene. This decision may have stemmed to non-castrated individuals. In addition, the castrates from the long-standing – but now outdated – knowledge exhibited significantly more behaviors that were indica- and belief about a lack of pain perception or reduced tive of pain, such as stiffness and trembling, as well as pain perception in neonates due to their immature nerv- scratching their rump and wagging their tails for at least ous systems (Baysinger et al., 2021). However, certain two days, and

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o their immature nerv- scratching their rump and wagging their tails for at least ous systems (Baysinger et al., 2021). However, certain two days, and maintained a huddled-up posture through- research results have proved increased pain perception out the period. However, no significant differences were in neonates (Mellor and Stafford, 2004; Baysinger et al., found in the levels of stress hormones in the urine of 2021), as vertebrates, including pigs, have neuroanatomi- castrates and entire male piglets, which was, however, cal structures related to pain perception similar to those inconsistent with findings of other authors who have ob- in humans (Baars, 2001; Sneddon et al., 2014; Baysinger served changes in stress-hormone levels in response to et al., 2021). the procedure (Prunier et al., 2005; Marchant-Forde et The surgical castration of entire male pigs without an- al., 2009; Maršálek et al., 2011; Lonardi et al., 2015). esthesia is highly controversial due to its adverse impact on In another experiment, Taylor and Weary (2000) stud- their welfare. The procedure not only triggers acute pain ied pain responses based on vocalization: pigs in one of but may also lead to pain or discomfort that can persist for their groups were castrated, while sham castrations were hours, days, or even weeks afterward (Rault et al., 2011). performed in the other. The castration procedure was The specifics of the procedure may vary across countries. divided into stages: restraint, washing the anogenital re- The procedure begins with restraining the piglet (by sus- gion (stages performed in both groups), incision of the pending it by its legs, placing it in a specialized castration scrotum, and severing/pulling the spermatic cord (the last stand, or holding it manually) to expose the

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s legs, placing it in a specialized castration scrotum, and severing/pulling the spermatic cord (the last stand, or holding it manually) to expose the anogenital re- two stages performed only in the castrated group). The gion (Hay et al., 2003). Subsequently, the scrotum is in- authors did not observe any differences in vocalization cised, with either two vertical cuts or one horizontal cut. during the period when all piglets underwent the same The testicles are then everted from the surrounding tissue, treatments from the initial stages (first and second stage). and the spermatic cord is severed using either a scalpel However, the castrated piglets emitted significantly more or an emasculator. A disinfectant is applied to the wound high-frequency sounds. The pain experienced by piglets and sometimes antibiotics are additionally administered during surgical castration has been documented in the lit- to prevent infection (Fredriksen et al., 2009; American erature, and research is underway to validate methods for Veterinary Medical Association, 2013). Despite repeated assessing pain scales in pigs (Ison et al., 2016; Viscardi questioning of the use of antibiotics in animal production, et al., 2017; Luna et al., 2020; Trindade et al., 2023; da they have been applied during the surgical castration of Silva et al., 2023; Robles et al., 2023). male piglets (Albernaz-Gonçalves et al., 2022). In a survey Despite substantial evidence indicating that the sur- study conducted by Fredriksen et al. (2009), the respond- gical castration worsens the welfare of male pigs, dis- ents from 10 out of the 26 analyzed countries reported us- continuation of this procedure could have serious con- ing antibiotics very often or always to prevent infections. sequences, like the development of

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continuation of this procedure could have serious con- ing antibiotics very often or always to prevent infections. sequences, like the development of boar taint in pork, as Notably, in Italy, the Netherlands, and Estonia, this prac- well as increased aggression and sexual behavior within tice was reported by over 50% of the respondents. One of herds. Additionally, it might expose farmers to higher the risks posed to human health by the use of antibiotics costs associated with implementing alternative methods. is the continuously growing antibiotic resistance, arousing Surgical castration without anesthesia is considered an another controversy among consumers (Barton, 2014). In economical approach, and limiting the prophylactic use addition, the castration procedure may cause certain com- of antibiotics can further reduce its cost, which usually plications such as hemorrhaging, swelling, and infection, ranges from €0.78 to €2.99 (Škrlep and Batorek-Lukač, potentially affecting performance, posing health risks, and 2023). even leading to fatalities of piglets (Hay et al., 2003; Mo- rales et al., 2017). Surgical castration with anesthesia and/or analgesia It is difficult to assess the degree of pain experienced A solution to mitigate pain during surgical castration by piglets during and after the procedure. As noted by may involve the use of anesthesia and/or analgesics. Pre- Surgical castration of piglets – challenges and alternatives 203 ventative measures include general or local anesthesia. ing on the pain relief method used. They also calculated General anesthesia can be administered via inhalation us- the costs: castration without anesthesia – €0.32 per pig- ing CO2/O2 or isoflurane, or intramuscularly using keta- let, castration using azaperone and

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the costs: castration without anesthesia – €0.32 per pig- ing CO2/O2 or isoflurane, or intramuscularly using keta- let, castration using azaperone and meloxicam – €3.14, mine. While CO2/O2 anesthesia is cost-effective, it poses castration with procaine and meloxicam – €3.30. a challenge related to administering an appropriate dose – essential to ensure unconsciousness but not lethal. Iso- Boar taint flurane anesthesia is more costly due to the equipment Boar taint poses a challenge to the pork meat industry, required (Bonneau and Weiler, 2019). What is more, it forcing the use of, among other things, strategies to mask elicits adverse environmental impacts because anesthetic it (Martínez et al., 2016). Its occurrence supports the advis- gases are greenhouse gases that contribute to climate ability of the castration practice. This unpleasant odor and change, and isoflurane, in particular, contains a chlorine flavor in the meat results from the accumulation of certain atom, which is implicated in ozone layer depletion and compounds in the adipose tissue, including primarily an- increases harmful ultraviolet radiation effects (Bara and drostenone, skatole, and indole compounds. The odor is Janczak, 2023). Piglets anesthetized via intramuscular in- described as urinous and fecal, and also resembling the jections using a combination of ketamine and azaperone odor of sweat or naphthalene (Duarte et al., 2021). Andros- experience prolonged recovery periods, during which tenone (5α-androst-16-en-3-one) is a steroid produced in they may suffer from motor coordination issues and low the Leydig cells of the testes, with its synthesis regulated blood pressure. These conditions can lead to hypothermia by the luteinizing hormone (LH), during sexual maturity or even

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with its synthesis regulated blood pressure. These conditions can lead to hypothermia by the luteinizing hormone (LH), during sexual maturity or even crushing by the sow. Another method harnessed and functions as a pheromone, influencing reproductive to alleviate pain during surgical castration is local anes- behaviors and indicating readiness for mating (Squires thesia, administered directly into the testes or spermatic et al., 2020). It is metabolized in the liver and testes and cord (Kluivers-Poodt, 2007). Lidocaine and procaine are then excreted in the urine. However, non-degraded andros- the most commonly used agents, with procaine being less tenone accumulates in the adipose tissue (Duarte et al., effective in some cases and the only approved local anes- 2021), and its odor is described as reminiscent of sweat, thetic for pigs in certain countries (Weiler and Bonneau, dirt, silage, and parsnip (Borrisser-Pairó et al., 2017). Ska- 2019). However, Skade et al. (2021) did not confirm its tole (3-methylindole) is produced in the large intestines of poorer efficacy in their study but observed that procaine pigs of both sexes upon tryptophan degradation by bacteria injections caused greater discomfort in piglets compared and accumulates in the adipose tissue if not degraded. Its to lidocaine injections. The efficacy of local anesthesia production depends on environmental factors, particularly also depends on the technique of administration and the diet and housing conditions, and, to a lesser extent, on ge- interval between injection and the procedure. Analgesic netic factors, and it is responsible for the fecal odor in pork drugs are commonly administered in addition to general (Duarte et al., 2021). Males cannot metabolize and elimi- and local anesthesia Meloxicam

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n pork drugs are commonly administered in addition to general (Duarte et al., 2021). Males cannot metabolize and elimi- and local anesthesia Meloxicam and flunixin are widely nate it through the liver because their sex steroids inhibit used to this end, though their standalone use does not these processes. Other compounds that potentially influ- alleviate pain during castration. Instead, they effec- ence the presence of boar taint by enhancing the effects of tively reduce post-procedure pain (Bonneau and Weiler, skatole and androstenone include aldehydes, short-chain 2019). Hansson et al. (2011) evaluated pain responses fatty acids, phenols (p-cresol, 4-ethylphenol), and 4-phe- in piglets castrated with anesthesia and observed that nyl-3-buten-2-one (Squires et al., 2020). lidocaine, administered directly to the testes, alleviated Heyrman et al. (2021) investigated the frequency and pain behaviors during the procedure, while meloxicam impact of aggressive behaviors among male pigs, includ- reduced responses afterward. Studies by Haga and Ra- ing related skin changes, as well as the influence of sea- nheim (2005), Hansson et al. (2011), and Kluivers-Poodt son of the year and lean meat content on the occurrence et al. (2012) confirmed changes in the physiology and/ of boar taint in meat across 22 farms (16,791 male pigs). or behavior of piglets subjected to surgical castration The average frequency of boar taint was 1.8±0.8% and with anesthesia that indicated the pain-relieving effect. varied between and within farms, which, according to In contrast, Sutherland et al. (2010, 2012), Viscardi and the authors, supported the hypothesis that the appearance Turner (2018) and Coutant et al. (2022 a, b) did not con- of odor depended on various factors. They observed that firm

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hypothesis that the appearance Turner (2018) and Coutant et al. (2022 a, b) did not con- of odor depended on various factors. They observed that firm any improvements in this regard. Opposite findings aggressive behavior may contribute to an increased inci- from these studies may be attributed to differences in the dence of boar taint, and that the odor was more prevalent anesthetics and/or analgesics used, as well as in dosing in the winter than in the summer. They attributed these and administration methods. observations to the shorter daylight hours and the associ- The use of pain-relieving measures during and after ated increased testicular activity in the male pigs. Also, castration is limited due to their efficacy, legal require- they found out that the boar taint was significantly less ments in different countries, and the costs borne by farm- perceptible in the pigs with a higher lean meat content. ers. Courboulay et al. (2010) estimated that local anesthe- Similarly, Thomsen et al. (2015) demonstrated increased sia increased labor requirements by 39–52%. Similarly, androstenone level in the winter compared to the sum- Scollo et al. (2021) reported labor- and time-consump- mer, while such season-dependent differences were not tion increases of 56.5% and 76.8%, respectively, depend- observed in skatole levels. 204 A. Zalewska et al. Attempts have been made to reduce the incidence Meier-Dinkel et al. (2013) and Borrisser-Pairó et al. of boar taint by modifying pigs’ diets based on the as- (2017) investigated consumer sensitivity to boar taint sumption that feeding may play a role in regulating the in meat. They observed significant subjectivity in odor levels of the compounds responsible for the odor–ska- assessment, with evaluations of consumer varying

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They observed significant subjectivity in odor levels of the compounds responsible for the odor–ska- assessment, with evaluations of consumer varying de- tole and indole. Among other factors, diet can influence pending on their sensitivity to odors. Borrisser-Pairó et a reduction in tryptophan availability by modifying the al. (2017) found out that consumers with a high sensi- endogenous microbiome, as well as gastrointestinal tivity to androstenone were more likely to reject meat transit time, and, thereby, the rate of absorption of ska- with boar taint. Their study also examined the impact of tole and indole (Bee et al., 2020). Hansen et al. (2008) meat processing methods (vacuum-cooked versus fried/ investigated the impact of administering high-fiber diets breaded with garlic and parsley) on consumer evaluation. for one or two weeks before slaughter on the occurrence The frying/breading method was found to increase the of boar taint. In their experiment, pigs were fed organ- acceptance of meat from entire male pigs, even among ic feed containing additives: dried chicory roots (10– consumers highly sensitive to androstenone. These pro- 13.3%) in the first group and blue lupine (25%) in the posed methods suggest potential solutions for the meat second group. They showed that the diet supplemented industry, such as implementing a classification system with lupine reduced the levels of skatole in blood and for tainted meat in slaughterhouses and using it in spe- fat, but had a negative impact on growth rate and feed cific products where the unpleasant odor can be masked. conversion. In turn, a reduced concentration of indole Literature works indicate that there are varying thresh- was determined in the pigs fed with chicory. Feeding olds for androstenone and

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tion of indole Literature works indicate that there are varying thresh- was determined in the pigs fed with chicory. Feeding olds for androstenone and skatole contents that are ac- male pigs dried chicory and lupine for two weeks before ceptable to consumers. In the 1990s, these thresholds slaughter reduced the sensory perception of boar taint were reported at 0.5 to 1 µg/g of fat for androstenone in the meat more effectively than the feeding for only and 0.2 to 0.25 µg/g of fat for skatole. However, later seven days. Other studies have also investigated the ef- consumer studies have shown that an androstenone level fect of dried chicory root on reducing boar taint, report- exceeding 1 µg/g of melted fat was still acceptable for ing positive results regarding its ability to lower skatole pork tenderloin (Meier-Dinkel et al., 2013). levels (Hansen et al., 2006; Maribo et al., 2010; Li et When deciding to forgo surgical castration, it is cru- al., 2019). Additionally, various strategies aimed at con- cial to pay particular attention to the methods for control- trolling skatole and indole levels have been explored as ling and detecting boar taint in meat. New investigations well. For instance, Zamaratskaia et al. (2005 c) observed on detection methods (Font-i-Furnols et al., 2020; Bur- a reduced level of skatole in the fat of entire male pigs geon et al., 2021) and on methods for reducing the odor fed raw potato starch. Similarly, Chen et al. (2007), us- (Squires et al., 2020; Duarte et al., 2021) still appear in ing the same additive, noted a decrease in skatole levels literature, highlighting the ongoing relevance of this is- in fat and plasma but no effect on indole levels. Büttner sue. et al. (2020) showed a reduced concentration of skatole in uncastrated male

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of this is- in fat and plasma but no effect on indole levels. Büttner sue. et al. (2020) showed a reduced concentration of skatole in uncastrated male pigs of the Piétrain breed by adding Aggression and sexual behavior in pens 10% native potato starch to their diet one month before The emergence of aggression and sexual behavior slaughter. Zamaratskaia et al. (2006) demonstrated re- within herds can pose a significant problem for swine duced levels of both skatole and indole in the liver of production and has a substantial adverse impact on ani- female pigs fed raw potato starch. In contrast, Aluwé mal welfare. The fattening of entire male pigs may exac- et al. (2009) did not observe a reduction in boar taint erbate the occurrence of aggressive and sexual behaviors after administering diets with varying percentages of due to the accumulation of sex hormones. Uncastrated raw potato starch. Vhile et al. (2012) found decreased individuals are more likely to fight for dominance within skatole concentrations in the large intestine and adipose a group, by biting, chasing, or striking, which may result tissue when using a diet with dried Jerusalem artichoke. in wounds, cuts, and abrasions. In addition to aggression, Similar results indicating reduced skatole levels in fat sexual behaviors are also problematic as uncastrated were achieved by Okrouhlá et al. (2020) when feeding males may experience leg injuries and lameness due to pigs Jerusalem artichoke. Reduced skatole levels in fat mounting behavior (Fredriksen et al., 2008). When com- were also observed when administering flaxseed to fe- paring the aggressive and sexual behaviors of females and male pigs (Kouba et al., 2003). However, skatole and uncastrated males, Rydhmer et al. (2004) observed more indole

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and sexual behaviors of females and male pigs (Kouba et al., 2003). However, skatole and uncastrated males, Rydhmer et al. (2004) observed more indole concentrations were higher in the adipose tissue injuries among entire male pigs, with 15% of all males of pigs fed a diet supplemented with garlic essential oil, and 6% of females exhibiting issues related to lameness with levels increasing as the additive concentration in- or leg injuries. Beside limb injuries, mounting can also creased (Leong et al., 2011). Marro et al. (2024) studied lead to penile injuries. Weiler et al. (2016) examined the effect of plant extracts on skatole levels in blood the penises of entire male pigs from both experimental and fat tissue. They also observed an increased skatole and commercial farms. They noted that 76.6–91.3% of concentration in pigs administered garlic essential oil, entire male pigs from the experimental farms had scars whereas oregano essential oil did not significantly af- and/or fresh wounds on their organ, while this problem fect the skatole concentration in either blood or fat. was observed in 64.0–94.9% of entire male pigs from the Surgical castration of piglets – challenges and alternatives 205 commercial farms. In addition to exhibiting aggression concentrations in the adipose tissue and androstenone in towards other individuals, uncastrated males can pose immunocastrated than entire males. a threat to the workers who handle them (Palmer et al., In addition to the positive impact on reducing boar 2018). Producers can minimize the problem of aggres- taint, immunocastration also minimizes the consequenc- sion by ensuring sufficient space in pens, unlimited ac- es of sexual behavior. Zoels et al. (2020) compared the cess to feed, grouping in pens by sex, early

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ensuring sufficient space in pens, unlimited ac- es of sexual behavior. Zoels et al. (2020) compared the cess to feed, grouping in pens by sex, early socialization frequency of penile injuries in entire male pigs and im- in groups, rare mixing between pens, and also by provid- munocastrated pigs. They showed that 91.7% of the en- ing natural materials that enrich the environment the pigs tire males exhibited signs of injuries, while in the im- are kept in (Borell et al., 2020). munocastrated individuals, this percentage ranged from Considering the impact of surgical castration of entire 16.7% to 41.7%. Similar results were obtained in an male pigs on their welfare, the behavioral and health con- experiment by Reiter et al. (2017), where the number sequences that may arise from aggressive and sexual be- of penile injuries in entire males was 75.8%, compared haviors cannot be overlooked. Foregoing surgical castra- to 48.4% recorded in the immunocastrated individuals. tion, while improving the welfare of piglets, may impair Zamaratskaia et al. (2008) compared the behaviors of the welfare of adult individuals, triggering aggression, entire males and immunocastrates, and showed no sig- attacks, and an increased frequency of injuries (Rydhmer nificant differences in the time spent sleeping, walking, et al., 2006). or eating. However, they observed that the immunocas- trated males exhibited fewer aggressive behaviors (biting Immunocastration the tails or ears of other pigs), social behaviors (pigs in- Immunocastration is one of several known alterna- teracting non-aggressively), and manipulative behaviors tives to surgical castration. It is performed by admin- (nibbling, pushing). Reducing aggressive behaviors not istering Improvac® (Zoetis, Belgium) in two injections only

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stration. It is performed by admin- (nibbling, pushing). Reducing aggressive behaviors not istering Improvac® (Zoetis, Belgium) in two injections only positively affects pig welfare but may also decrease (Wicks et al., 2013). This product was approved for water consumption (Muniz et al., 2021). market use in the EU in May 2009 (Zamaratskaia and Despite the many proven positive effects of immu- Rasmussen, 2015). According to the manufacturer’s nocastration, this method has certain drawbacks. These recommendations, it should be administered subcutane- include the costs associated with purchasing the product, ously using safe devices designed for this purpose. The as well as the labor required for the injections (Bonneau first dose of the product is given to uncastrated males at and Weiler, 2019). De Roest et al. (2009) estimated the the age of eight to nine weeks, and the next dose no ear- cost of immunocastration at €3 to €3.36 per pig, depend- lier than four weeks after the first, but four to six weeks ing on the country. Another issue is the social acceptance before slaughter. of immunocastration; consumers have concerns about Immunocastration induces an immune response the potential presence of residues in meat (Fredriksen et against the endogenous gonadotropin-releasing factor al., 2011; Kress et al., 2019). Their critical stance was (GnRF), which is responsible for regulating testicular confirmed by the results of a study by Heid and Hamm function through the gonadotropic hormones LH and (2012), which analyzed the attitudes of German con- FSH. It is expected to inhibit testicular development, and sumers towards immunocastration and showed that the thus reduce sex hormone production (Bonneau and Weil- respondents were worried about, among other things, er,

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rds immunocastration and showed that the thus reduce sex hormone production (Bonneau and Weil- respondents were worried about, among other things, er, 2019). The full effect of immunocastration is achieved hormone residues in the meat they consumed. Addition- only after the second dose of the product. Although the ally, handling heavy pigs for subsequent injections can first dose does not modify testicular functions, it prepares be challenging, prompting some farmers to consider the the animal for the immune response to GnRF upon ad- method impractical (Brunius et al., 2011). Lin-Schilstra ministration of the second dose (Weiler et al., 2021). and Ingenbleek (2022) conducted a scenario analysis for The reduction in sex hormone production result- implementing immunocastration as a single solution for ing from immunocastration decreases the frequency of piglet castration. In their study, two extreme scenarios boar taint occurrence. An experiment by Fazarinc et al. were constructed in which all the ambiguous issues re- (2023) demonstrated that the concentration of andros- garding immunocastration were viewed either positively tenone exceeded the threshold of 0.5 µg/g in 81.8% of or negatively. The authors concluded that there was a low the commercial, hybrid entire male pigs, while in a group likelihood that immunocastration could be implemented subjected to immunocastration, the percentage was only as the sole alternative to surgical castration in entire male 4.3% of the males. Results confirming reduced levels pigs. of sex hormones in entire male pigs of the WBP (Pol- An important aspect is providing an appropriate ish Large White) breed slaughtered at a body weight of diet for immunocastrated pigs. Nutrition plays a crucial 120 kg were obtained in an experiment by

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h Large White) breed slaughtered at a body weight of diet for immunocastrated pigs. Nutrition plays a crucial 120 kg were obtained in an experiment by Pawlicki et role in growth performance, carcass quality, and overall al. (2022). In the blood serum and testes of immunocas- health. Bee et al. (2020) highlighted the specific dietary trated males, lower levels of androstenone, testosterone, needs of immunocastrates, particularly their amino acid and estradiol were found. Reduced hormone levels were requirements. Decreased levels of sex hormones after the also demonstrated by Brunius et al. (2011), Metz et al. second vaccine dose trigger metabolic changes, which (2002), and Han et al. (2019) who reported lower skatole was confirmed by lysine requirements decrease by up to 206 A. Zalewska et al. 30% in the immunocastrated pigs compared to the entire To address the issue of boar taint in meat from intact male pigs. Muniz et al. (2019) found out that also the im- male pigs, researchers have examined the link between munocastrated pigs required more lysine than the surgi- its occurrence and the sexual maturity of these animals. cally castrated males. This correlation arises from the increasing synthesis of androstenone with sexual development. A similar rela- Fattening entire male pigs tionship has been observed for skatole levels, likely due Besides unwanted consequences such as boar taint to the inhibition of skatole degradation by androstenone and aggression, fattening entire male pigs has also posi- and other sex steroids (Larzul, 2021). A correlation be- tive outcomes. The feed conversion of entire male pigs tween skatole and androstenone levels was also demon- is more efficient and ensures higher lean meat deposi- strated by Zamaratskaia et al. (2004). Babol et al.

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ole and androstenone levels was also demon- is more efficient and ensures higher lean meat deposi- strated by Zamaratskaia et al. (2004). Babol et al. (2004) tion, thereby boosting production profitability (Daxan- examined the impact of maturation on skatole levels in berger et al., 2001; De Roest et al., 2009; Škrlep et al., plasma. They observed low skatole levels at 150–180 2020). days of age, which increased during the 180–190 to 240– Kress et al. (2020), who compared carcass quality 360-day range, depending on the pig breed. In another based on sex (entire male pigs, gilts, barrows), showed study, Zamaratskaia et al. (2005 a) noted a relationship that the carcasses of entire male pigs contained the most between body weight and plasma levels of compounds lean meat and had thinner backfat compared to those of responsible for boar taint. Skatole and testicular steroid the castrated individuals. They also showed that the com- levels in plasma were higher in the pigs weighing 115 kg bined mass of valuable carcass elements in entire male compared to those with lower body weights (90 and 100 pigs was 48.33±0.16 kg/carcass, which was not statisti- kg). Further on, Zamaratskaia et al. (2005 b) found as- cally significantly higher compared to immunocastrates sociations between skatole and androstenone levels and or barrows, but significantly lower than in gilts. factors related to maturation, such as gonadal hormone Aaslyng et al. (2019) reported that the carcasses of levels and reproductive organ size. Slaughtering pigs at entire male pigs showed a higher meat content compared lower body weights can also influence carcass and meat to castrates, but that the meat obtained from entire males quality. Fàbrega et al. (2011) showed that the meat from was less tender and

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rcass and meat to castrates, but that the meat obtained from entire males quality. Fàbrega et al. (2011) showed that the meat from was less tender and had a lower protein content. Oppo- pigs slaughtered at 105 kg exhibited significantly higher site observations were made by Lundström et al. (2009), lightness (L*) and higher drip loss compared to the meat who stated that the carcasses of entire males were char- from pigs slaughtered at 130 kg. Additionally, carcasses acterized by better quality and higher protein content of from the pigs slaughtered at a live weight of 105 kg had the meat than those of the castrates. Aaslyng and Hviid a higher percentage of lean meat. (2020) studied meat quality in the Danish pig population Despite findings indicating a relationship between by randomly selecting entire male pigs, gilts, and bar- sexual maturity and boar taint, there is no universal age rows from various slaughterhouses. They demonstrated or body weight at which boar taint-free meat can consist- that the meat from the pigs of each sex was of high qual- ently be obtained from entire male pigs. ity with a low coefficient of variation for pH and color. In addition, they observed increased drip loss from the Other alternatives meat of entire male pigs and higher shear-force values. In addition to the most commonly used alternatives Another important aspect concerning entire male pigs, to surgical castration of male pigs (immunocastration besides the quality of meat, is in using their meat in pro- and fattening of entire males), other methods are being cessing and as raw material. An experiment by Škrlep investigated that could potentially minimize the conse- et al. (2016), which tested the suitability of meat from quences of abandoning the procedure. However, these entire

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ld potentially minimize the conse- et al. (2016), which tested the suitability of meat from quences of abandoning the procedure. However, these entire male pigs and immunocastrates for dry-cured ham methods should not be regarded as viable solutions to production, showed that hams from the entire males had the problem, as they remain in the research phase. One higher processing losses than those from the immuno- of these is genetic selection aimed at reducing the com- castrated males. This could be related to a higher muscle pounds responsible for boar taint. This is possible due to mass and a lower intramuscular fat (IMF) content, mak- the highly heritable nature of androstenone (0.55–0.88) ing the hams from the entire males drier, less marbled, and skatole (0.23–0.55) (Duarte et al., 2021). As a result, tougher, and more intensely colored. it seems feasible to select individuals in which boar taint Despite the information available in the literature in- is reduced (Tajet et al., 2006; Squires, 2006; Parois et al., dicating the presence of boar taint in the meat from entire 2015). However, this method carries the risk of repro- male pigs, it may be utilized for processing. Wauters et al. ductive losses because androstenone synthesis is linked (2017) suggested that meat affected by boar taint could to other testicular steroids, which can adversely impact be used to produce cold-served meat products. In turn, sexual maturity (Duarte et al., 2021). Mörlein et al. (2019) stated that up to 33% of the meat Another method entails the use of sexed semen, which and fat from carcasses in which the melted fat had ska- would allow for the fattening of gilts only, potentially tole concentrations of up to 0.3 μg/g and androstenone eliminating the problem of boar taint

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would allow for the fattening of gilts only, potentially tole concentrations of up to 0.3 μg/g and androstenone eliminating the problem of boar taint entirely (Čandek- concentrations of up to 3.8 μg/g, could be used in the Potokar and Batorek-Lukač, 2015). Although technolo- production of high-fat sausages. gies for differentiating sperm based on sex chromosomes Surgical castration of piglets – challenges and alternatives 207 do exist, there are issues related to the availability of this Babol J., Zamaratskaia G., Juneja R.K., Lundström K. (2004). The ef- semen for commercial production. Performing deep in- fect of age on distribution of skatole and indole levels in entire male pigs in four breeds: Yorkshire, Landrace, Hampshire and trauterine insemination requires a large number of sperm Duroc. Meat Sci., 67: 351–358. cells (Waberski et al., 2019). Additionally, such sperm Bara M., Janczak A. (2023). Toxicity of anesthetic gases: exposure cells are more susceptible to damage, and their use in in operating rooms and influence on the environment. Prospect. fertilization is characterized by lower efficiency (Gaudy, Pharm. Sci., 21: 1–5. Barton M.D. (2014). Impact of antibiotic use in the swine indus- 2014; Quelhas et al., 2023). This method is particularly try. Curr. Opin. Microbiol., 19: 9–15. costly and requires skilled personnel to execute (Quelhas Baysinger A., Webb S.R., Brown J., Coetzee J.F., Crawford S., et al., 2023). DeDecker A., Karriker L.A., Pairis-Garcia M., Sutherland A.M., Viscardi A.V. (2021). Proposed multidimensional pain outcome methodology to demonstrate analgesic drug efficacy and facili- Conclusions tate future drug approval for piglet castration. Anim. Health Res. Surgical castration causes pain to piglets and nega- Rev., 22:

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facili- Conclusions tate future drug approval for piglet castration. Anim. Health Res. Surgical castration causes pain to piglets and nega- Rev., 22: 163–176. tively impacts their welfare. Consumer pressure has Bee G., Quiniou N., Maribo H., Zamaratskaia G., Lawlor P.G. (2020). forced producers and administrative bodies to take steps Strategies to meet nutritional requirements and reduce boar taint in meat from entire male pigs and immunocastrates. Animals, to introduce alternative methods. The most popular al- 10. ternatives include the use of pain-relieving methods, im- Bonneau M., Weiler U. (2019). Pros and cons of alternatives to piglet munocastration, and the fattening of entire male pigs. castration: Welfare, boar taint, and other meat quality traits. Ani- Each of these methods has certain consequences, such mals, 9. as increased production costs, changes in behavior and Borell E.V., Bonneau M., Holinger M., Prunier A., Stefanski V., Zöls S., Weiler U. (2020). Welfare aspects of raising entire male pigs welfare of individuals, handling difficulties, the presence and immunocastrates. Animals, 10. of boar taint, and negative impacts on the quality of pork. Borrisser-Pairo F., Panella-Riera N., Gil M., Kallas Z., Linares M.B., Therefore, it is essential to choose a method that consid- Egea M., Garrido M.D., Oliver M.A. (2017). Consumers’ sensitiv- ers pig welfare, does not significantly increase produc- ity to androstenone and the evaluation of different cooking meth- ods to mask boar taint. Meat Sci., 123: 198–204. tion costs compared to barrow fattening, and allows con- Brunius C., Zamaratskaia G., Andersson K., Chen G., Norrby M., sumers to consume pork in line with their sensitivity to Madej A., Lundström K. (2011). Early immunocastration of male pig

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son K., Chen G., Norrby M., sumers to consume pork in line with their sensitivity to Madej A., Lundström K. (2011). Early immunocastration of male pig rearing conditions. pigs with Improvac® – Effect on boar taint, hormones and repro- ductive organs. Vaccine, 29: 9514–9520. Burgeon C., Debliquy M., Lahem D., Rodriguez J., Ly A., Fauconnier Acknowledgements M.L. (2021). Past, present, and future trends in boar taint detec- The paper is a part of the PhD thesis of Anna Zalewska. tion. Trends Food Sci. Technol., 112: 283–297. Büttner S., Heidbüchel K., Höinghaus K., Baldinger L., Weissmann F., Disclosures Bussemas R. (2020). Fattening of entire male pigs as an alterna- The authors declare that there is no conflict of inter- tive to piglet castration. Thünen Institut of Organic Farming, 15. Čandek-Potokar M., Batorek-Lukač N. (2015). Alternatives to surgical est. castration of pigs. Bulg. J. Anim. Husb., 52: 41–51. Chen G., Zamaratskaia G., Andersson H.K., Lundström K. (2007). Effects of raw potato starch and live weight on fat and plasma skatole, indole and androstenone levels measured by different References methods in entire male pigs. Food Chem., 101: 439–448. Council Directive 2008/120/EC of 18 December 2008 laying down Aaslyng M.D., Hviid M. (2020). Meat quality in the Danish pig popu- minimum standards for the protection of pigs (codified version). lation anno 2018. Meat Sci., 163. Courboulay V., Hemonic A., Gadonna M., Prunier A. (2010). Castra- Aaslyng M.D., Støier S., Lund B.W., Nielsen D.B. (2019). Slaughter- tion avec anesthésie locale ou traitement anti-inflammatoire: quel ing of entire male pigs seen from the slaughterhouse perspective. impact sur la douleur des porcelets et quelles conséquences sur le IOP Conf. Ser: Earth Environ. Sci.,

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pigs seen from the slaughterhouse perspective. impact sur la douleur des porcelets et quelles conséquences sur le IOP Conf. Ser: Earth Environ. Sci., 333: 1–6. travail en élevage. Journées Rech. Porcine, 42: 27–33. Albernaz-Gonçalves R., Antillón G.O., Hötzel M.J. (2022). Linking Coutant M., Malmkvist J., Kaiser M., Foldager L., Herskin M.S. (2022 animal welfare and antibiotic use in pig farming – a review. Ani- a). Piglets’ acute responses to local anesthetic injection and sur- mals, 12: 216. gical castration: Effects of the injection method and interval be- Aluwé M., Millet S., Nijs G., Tuyttens F.A.M., Verheyden K., De tween injection and castration. Front. Vet. Sci., 9. Brabander H.F., De Brabander D.L., Van Oeckel M.J. (2009). Ab- Coutant M., Malmkvist J., Kaiser M., Foldager L., Herskin M.S. (2022 sence of an effect of dietary fibre or clinoptilolite on boar taint in b). Piglets’ acute responses to procaine-based local anesthetic in- entire male pigs fed practical diets. Meat Sci., 82: 346–352. jection and surgical castration: Effects of two volumes of anes- Aluwé M., Heyrman E., Almeida J.M., Babol J., Battacone G., Čítek thetic. Front. Pain Res., 3. J., Font i Furnols M., Getya A., Karolyi D., Kostyra E., Kress K., Czech A., Kusior G., Zięba G., Łukaszewicz M., Grela E.R. (2022). Kušec G., Mörlein D., Semenova A., Škrlep M., Stoyanchev T., Effect of immunocastration on the steroid hormones content, se- Tomašević I., Tudoreanu L., Van Son M., Żakowska-Biemans S., rum lipid profile, and fatty acid profile in tissues of porkers fed dry Zamaratskaia G., Van den Broeke A., Egea M. (2020). Explor- or wet diet. Anim. Sci. Pap. Rep., 40: 171–184. atory survey on European consumer and stakeholder attitudes to- da Silva G.V., Pivato G.M.,

excerpt 27

). Explor- or wet diet. Anim. Sci. Pap. Rep., 40: 171–184. atory survey on European consumer and stakeholder attitudes to- da Silva G.V., Pivato G.M., Peres B.G., Luna S.P.L., Pairis-Garcia wards alternatives for surgical castration of piglets. Animals, 10. M.D., Trindade P.H.E. (2023). Simplified assessment of castra- American Veterinary Medical Association. (2013). Literature review tion-induced pain in pigs using lower complexity algorithms. Sci. on the welfare implications of swine castration. Available online: Rep., 13. https://www.avma.org/resources-tools/literature-reviews/welfare- Daxenberger A., Hageleit M., Kraetzl W.D., Lange I.G., Claus R., Le implications-swine-castration Bizec B., Meyer H.H. (2001). Suppression of androstenone in Baars B.J. (2001). There are no known differences in brain mechanisms entire male pigs by anabolic preparations. Livest. Prod. Sci., 69: of consciousness between humans and other mammals. Anim. 139–144. Welfare, 10: 31–40. De Roest K., Montanari C., Fowler T., Baltussen W. (2009). Resource 208 A. Zalewska et al. efficiency and economic implications of alternatives to surgical Kluivers-Poodt M., Houx B.B., Robben S.R.M., Koop G., Lam- castration without anaesthesia. Animal, 3: 1522–1531. booij E., Hellebrekers L.J. (2012). Effects of a local anaesthetic Di Pasquale J., Vecchio Y., Martelli G., Sardi L., Adinolfi F., Nannoni and NSAID in castration of piglets, on the acute pain responses, E. (2020). Health risk perception, consumption intention, and growth and mortality. Animal, 6: 1469–1475. willingness to pay for pig products obtained by immunocastra- Kouba M., Enser M., Whittington F.M., Nute G.R., Wood J.D. (2003). tion. Animals, 10. Effect of a high-linolenic acid diet on lipogenic enzyme activi- Duarte D.A.S.,

excerpt 28

M., Whittington F.M., Nute G.R., Wood J.D. (2003). tion. Animals, 10. Effect of a high-linolenic acid diet on lipogenic enzyme activi- Duarte D.A.S., Schroyen M., Mota R.R., Vanderick S., Gengler N. ties, fatty acid composition, and meat quality in the growing pig. J. (2021). Recent genetic advances on boar taint reduction as an Anim. Sci., 81: 1967–1979. alternative to castration: a review. J. Appl. Genet., 62: 137–150. Kress K., Millet S., Labussière É., Weiler U., Stefanski V. (2019). Fàbrega E., Velarde A., Cros J., Gispert M., Suárez P., Tibau J., Soler Sustainability of pork production with immunocastration in Eu- J. (2010). Effect of vaccination against gonadotrophin-releasing rope. Sustainability, 11. hormone, using Improvac®, on growth performance, body com- Kress K., Hartung J., Jasny J., Stefanski V., Weiler U. (2020). Carcass position, behaviour and acute phase proteins. Livest. Sci., 132: characteristics and primal pork cuts of gilts, boars, immunocas- 53–59. trates and barrows using AutoFOM III data of a commercial abat- Fàbrega E., Gispert M., Tibau J., Hortós M., Oliver M.A., Font i Furn- toir. Animals, 10. ols M. (2011). Effect of housing system, slaughter weight and Larzul C. (2021). How to improve meat quality and welfare in entire slaughter strategy on carcass and meat quality, sex organ develop- male pigs by genetics. Animals, 11. ment and androstenone and skatole levels in Duroc finished entire Leong J., Morel P.C., Purchas R.W., Wilkinson B.H. (2011). Effects male pigs. Meat Sci., 89: 434–439. of dietary components including garlic on concentrations of ska- Fazarinc G., Batorek-Lukač N., Škrlep M., Poklukar K., Van den tole and indole in subcutaneous fat of female pigs. Meat Sci., 88: Broeke A., Kress K., Labussiѐre E.,

excerpt 29

torek-Lukač N., Škrlep M., Poklukar K., Van den tole and indole in subcutaneous fat of female pigs. Meat Sci., 88: Broeke A., Kress K., Labussiѐre E., Stefanski V., Vrecl M., 45–50. Čandek-Potokar M. (2023). Male reproductive organ weight: cri- Li X., Jensen B.B., Canibe N. (2019). The mode of action of chicory teria for detection of androstenone-positive carcasses in immuno- roots on skatole production in entire male pigs is neither via reduc- castrated and entire male pigs. Animals, 13. ing the population of skatole-producing bacteria nor via increased Font-i-Furnols M., Martín-Bernal R., Aluwé M., Bonneau M., Haugen butyrate production in the hindgut. Appl. Environ. Microb., 85. J.E., Mörlein D., Panella-Riera N., Škrlep M. (2020). Feasibility Lin-Schilstra L., Ingenbleek P.T. (2021). Examining alternatives to of on/at line methods to determine boar taint and boar taint com- painful piglet castration within the contexts of markets and stake- pounds: An overview. Animals, 10. holders: A comparison of four EU countries. Animals, 11. Fredriksen B., Lium B.M., Marka C.H., Mosveen B., Nafstad O. Lin-Schilstra L., Ingenbleek P.T. (2022). A scenario analysis for imple- (2008). Entire male pigs in farrow-to-finish pens – Effects on ani- menting immunocastration as a single solution for piglet castra- mal welfare. Appl. Anim. Behav. Sci., 110: 258–268. tion. Animals, 12. Fredriksen B., Font i Furnols M.F., Lundström K., Migdal W., Prunier Lonardi C., Scollo A., Normando S., Brscic M., Gottardo F. (2015). A., Tuyttens F.A., Bonneau M. (2009). Practice on castration of Can novel methods be useful for pain assessment of castrated pig- piglets in Europe. Animal, 3: 1480–1487. lets? Animal, 9: 871–877. Fredriksen B., Johnsen A.M.S., Skuterud E. (2011). Consumer

excerpt 30

sment of castrated pig- piglets in Europe. Animal, 3: 1480–1487. lets? Animal, 9: 871–877. Fredriksen B., Johnsen A.M.S., Skuterud E. (2011). Consumer at- Luna S.P.L., de Araújo A.L., da Nóbrega Neto P.I., Brondani J.T., de titudes towards castration of piglets and alternatives to surgical Oliveira F.A., Azerêdo L.M.D.S., Telles F.G., Trindade P.H.E. castration. Res. Vet. Sci., 90: 352–357. (2020). Validation of the UNESP-Botucatu pig composite acute Gaudy J. (2014). Alternatives to surgical castration in pigs: a re- pain scale (UPAPS). PLoS One, 15. view. Indian J. Anim. Prod. Mgmt., 30: 1–6. Lundström K., Matthews K.R., Haugen J.E. (2009). Pig meat quality Haga H.A., Ranheim B. (2005). Castration of piglets: the analgesic ef- from entire males. Animal, 3: 1497–1507. fects of intratesticular and intrafunicular lidocaine injection. Vet. Mancini M.C., Menozzi D., Arfini F. (2017). Immunocastration: Anaesth. Analg., 32: 1–9. Economic implications for the pork supply chain and consumer Han X., Zhou M., Cao X., Du X., Meng F., Bu G., Kong F., Huang perception. An assessment of existing research. Livest. Sci., 203: A., Zeng X. (2019). Mechanistic insight into the role of immuno- 10–20. castration on eliminating skatole in boars. Theriogenology, 131: Marchant-Forde J.N., Lay D.C., McMunn K.A., Cheng H.W., Pajor 32–40. E.A., Marchant-Forde R.M. (2009). Postnatal piglet husbandry Hansen L.L., Mejer H., Thamsborg S.M., Byrne D.V., Roepstorff practices and well-being: the effects of alternative techniques de- A., Karlsson A.H., Hansen-Møller J., Jensen M.T., Tuomola M. livered separately. J. Anim. Sci., 87: 1479–1492. (2006). Influence of chicory roots (Cichorium intybus L.) on boar Maribo H., Magnussen C.C., Jensen B.B. (2010). Effect of 15% dried taint

excerpt 31

1479–1492. (2006). Influence of chicory roots (Cichorium intybus L.) on boar Maribo H., Magnussen C.C., Jensen B.B. (2010). Effect of 15% dried taint in entire male and female pigs. Anim. Sci., 82: 359–368. chicory root in feed for male pigs. Meddelelse, 876. Hansen L.L., Stolzenbach S., Jensen J.A., Henckel P., Hansen-Møller Marro P., Wesoly R., Stefanski V. (2024). Influence of different plant J., Syriopoulos K., Byrne D.V. (2008). Effect of feeding ferment- extracts on CYP-mediated skatole and indole degradation in able fibre-rich feedstuffs on meat quality with emphasis on chemi- pigs. Animals, 14: 888. cal and sensory boar taint in entire male and female pigs. Meat Maršálek P., Svoboda M., Smutná M., Blahová J., Večerek V. (2011). Sci., 80: 1165–1173. Neopterin and biopterin as biomarkers of immune system acti- Hansson M., Lundeheim N., Nyman G., Johansson G. (2011). Effect vation associated with castration in piglets. J. Anim. Sci., 89: of local anaesthesia and/or analgesia on pain responses induced by 1758–1762. piglet castration. Acta Vet. Scand., 53: 1–9. Martínez B., Rubio B., Viera C., Linares M.B., Egea M., Panella-Riera Hay M., Vulin A., Génin S., Sales P., Prunier A. (2003). Assessment N., Garrido M.D. (2016). Evaluation of different strategies to of pain induced by castration in piglets: behavioral and physio- mask boar taint in cooked sausage. Meat Sci., 116: 26–33. logical responses over the subsequent 5 days. Appl. Anim. Behav. Meier-Dinkel L., Sharifi A.R., Tholen E., Frieden L., Bücking M., Sci., 82: 201–218. Wicke M., Mörlein D. (2013). Sensory evaluation of boar loins: Heid A., Hamm U. (2012). Consumer attitudes towards alternatives to Trained assessors’ olfactory acuity affects the perception of boar piglet castration

excerpt 32

id A., Hamm U. (2012). Consumer attitudes towards alternatives to Trained assessors’ olfactory acuity affects the perception of boar piglet castration without pain relief in organic farming: Qualita- taint compounds. Meat Sci., 94: 19–26. tive results from Germany. J. Agr. Environ. Ethics, 25: 687–706. Mellor D.J., Stafford K.J. (2004). Animal welfare implications of Heyrman E., Millet S., Tuyttens F.A.M., Ampe B., Janssens S., Buys neonatal mortality and morbidity in farm animals. Vet. J., 168: N., Wauters J., Vanhaecke L., Aluwé M. (2021). On-farm preva- 118–133. lence of and potential risk factors for boar taint. Animal, 15. Metz C., Hohl K., Waidelich S., Drochner W., Claus R. (2002). Ac- Ison S.H., Clutton R.E., Di Giminiani P., Rutherford K.M. (2016). A tive immunization of boars against GnRH at an early age: con- review of pain assessment in pigs. Front. Vet. Sci., 3. sequences for testicular function, boar taint accumulation and N- Kluivers-Poodt M. (2007). Castration under anaesthesia and/or anal- retention. Livest. Prod. Sci., 74: 147–157. gesia in commercial pig production. Anim. Sci. Group, 85: 1–2. Morales J., Dereu A., Manso A., de Frutos L., Piñeiro C., Manzanilla Surgical castration of piglets – challenges and alternatives 209 E.G., Wuyts N. (2017). Surgical castration with pain relief affects M.D., Linares M.B., Peñaranda I., Aluwé M., Font-i-Furnols M. the health and productive performance of pigs in the suckling pe- (2020). The use of pork from entire male and immunocastrated riod. Porcine Health Manage., 3: 1–6. pigs for meat products – An overview with recommendations. An- Mörlein J., Meier-Dinkel L., Gertheiss J., Schnäckel W., Mörlein D. imals, 10. (2019). Sustainable use of tainted boar meat: Blending is a strat- Sneddon

excerpt 33

lein J., Meier-Dinkel L., Gertheiss J., Schnäckel W., Mörlein D. imals, 10. (2019). Sustainable use of tainted boar meat: Blending is a strat- Sneddon L.U., Elwood R.W., Adamo S.A., Leach M.C. (2014). Defin- egy for processed products. Meat Sci., 152: 65–72. ing and assessing animal pain. Anim. Behav., 97: 201–212. Muniz H.D.C.M., da Rocha L.T., Kunzler J.S., Ceron M.S., Fraga Squires E.J. (2006). Possibilities for selection against boar taint. Acta B.N., Bottan J., de Quadros A.R.B., de Oliveira V. (2019). Evalu- Vet. Scand., 48. ation of factorial methods to estimate lysine requirements for bar- Squires E.J., Bone C., Cameron J. (2020). Pork production with entire rows and immunocastrated pigs. Livest. Sci., 227: 68–74. males: Directions for control of boar taint. Animals, 10. Muniz H.D.C.M., Klein D.R., dos Santos M.D.S., Schneider L.I., Ce- Sutherland M.A., Davis B.L., Brooks T.A., McGlone J.J. (2010). Phys- ron M.S., de Quadros A.R.B., Eliseu C., de Oliveira V. (2021). iology and behavior of pigs before and after castration: effects of Water intake and wastage during the growing–finishing period two topical anesthetics. Animal, 4: 2071–2079. of immunocastrated and surgically castrated pigs. Anim. Prod. Sutherland M.A., Davis B.L., Brooks T.A., Coetzee J.F. (2012). The Sci., 61: 1385–1392. physiological and behavioral response of pigs castrated with and Okrouhlá M., Čítek J., Švejstil R., Zadinová K., Pokorná K., Urbanová without anesthesia or analgesia. J. Anim. Sci., 90: 2211–2221. D., Stupka R. (2020). The effect of dietary Helianthus tuberosus Tajet H., Andresen Ø., Meuwissen T.H.E. (2006). Estimation of ge- L. on the populations of pig faecal bacteria and the prevalence of netic parameters of boar taint; skatole and androstenone and

excerpt 34

06). Estimation of ge- L. on the populations of pig faecal bacteria and the prevalence of netic parameters of boar taint; skatole and androstenone and their skatole. Animals, 10: 693. correlations with sexual maturation. Acta Vet. Scand., 48. Palmer C., Pedersen H.G., Sandøe P. (2018). Beyond castration and Taylor A.A., Weary D.M. (2000). Vocal responses of piglets to castra- culling: Should we use non-surgical, pharmacological methods to tion: identifying procedural sources of pain. Appl. Anim. Behav. control the sexual behavior and reproduction of animals?. J. Agr. Sci., 70: 17–26. Environ. Ethics, 31: 197–218. Thomsen R., Edwards S.A., Jensen B.B., Rousing T., Sorensen J.T. Parois S.P., Prunier A., Mercat M.J., Merlot E., Larzul C. (2015). (2015). Weight and season affects androstenone and skatole oc- Genetic relationships between measures of sexual development, currence in entire male pigs in organic pig production. Animal, boar taint, health, and aggressiveness in pigs. J. Anim. Sci., 93: 9: 1577–1586. 3749–3758. Trindade P.H.E., Lopez-Soriano M., Merenda V.R., Tomacheuski Pawlicki P., Galuszka A., Pardyak L., Tuz R., Płachno B.J., Malo- R.M., Pairis-Garcia M.D. (2023). Effects of assessment method polska M., Dubniewicz K., Yang P., Kotula-Balak M., Tarasiuk (real-time versus video-recorded) on a validated pain-altered be- K. (2022). Leydig cells in immunocastrated Polish Landrace pig havior scale used in castrated piglets. Sci. Rep., 13. testis: differentiation status and steroid enzyme expression sta- Vhile S.G., Kjos N.P., Sørum H., Øverland M. (2012). Feeding Jerusa- tus. Int. J. Mol. Sci., 23. lem artichoke reduced skatole level and changed intestinal micro- Prunier A., Mounier A.M., Hay M. (2005). Effects of castration, tooth biota in the gut of

excerpt 35

rtichoke reduced skatole level and changed intestinal micro- Prunier A., Mounier A.M., Hay M. (2005). Effects of castration, tooth biota in the gut of entire male pigs. Animal, 6: 807–814. resection, or tail docking on plasma metabolites and stress hor- Viscardi A.V., Turner P.V. (2018). Use of meloxicam or ketoprofen mones in young pigs. J. Anim. Sci., 83: 216–222. for piglet pain control following surgical castration. Front. Vet. Quelhas J., Pinto-Pinho P., Lopes G., Rocha A., Pinto-Leite R., Fardi- Sci., 5. lha M., Colaço B. (2023). Sustainable animal production: explor- Viscardi A.V., Hunniford M., Lawlis P., Leach M., Turner P.V. (2017). ing the benefits of sperm sexing technologies in addressing critical Development of a piglet grimace scale to evaluate piglet pain us- industry challenges. Front. Vet. Sci., 10. ing facial expressions following castration and tail docking: a pilot Rault J.L., Lay D.C., Marchant J.N. (2011). Castration induced pain in study. Front. Vet. Sci., 4. pigs and other livestock. Appl. Anim. Behav. Sci., 135: 214–225. Waberski D., Riesenbeck A., Schulze M., Weitze K.F., Johnson L. Reiter S., Zöls S., Ritzmann M., Stefanski V., Weiler U. (2017). Penile (2019). Application of preserved boar semen for artificial insemi- injuries in immunocastrated and entire male pigs of one fattening nation: Past, present and future challenges. Theriogenology, 137: farm. Animals, 7. 2–7. Robles I., Luna S.P.L., Trindade P.H.E., Lopez-Soriano M., Merenda Wauters J., Verplanken K., Vercruysse V., Ampe B., Aluwé M., Van- V.R., Viscardi A.V., Tamminga E., Pairis-Garcia M.D. (2023). haecke L. (2017). Sensory evaluation of boar meat products by Validation of the Unesp-Botucatu pig composite acute pain scale trained experts. Food Chem., 237: 516–524.

excerpt 36

Sensory evaluation of boar meat products by Validation of the Unesp-Botucatu pig composite acute pain scale trained experts. Food Chem., 237: 516–524. (UPAPS) in piglets undergoing castration. PloS one, 18. Weiler U., Bonneau M. (2019). Why it is so difficult to end surgical Rydhmer L., Zamaratskaia G., Andersson H.K., Algers B., Lundström castration of boars in Europe: Pros and cons of alternatives to pig- K. (2004). Problems with aggressive and sexual behaviour when let castration. IOP Conf. Ser.: Environ. Earth Sci., 333. rearing entire male pigs. Proc. 55th Annual Meeting of the Euro- Weiler U., Isernhagen M., Stefanski V., Ritzmann M., Kress K., Hein pean Association for Animal Production, Bled, Slovenia, 4. C., Zöls S. (2016). Penile injuries in wild and domestic pigs. Ani- Rydhmer L., Zamaratskaia G., Andersson H.K., Algers B., Guil- mals, 6. lemet R., Lundström K. (2006). Aggressive and sexual behaviour Weiler U., Font-i-Furnols M., Tomasevič I., Bonneau M. (2021). Al- of growing and finishing pigs reared in groups, without castra- ternatives to piglet castration: from issues to solutions. Animals, tion. Acta Agric. Scand. Section A, 56: 109–119. 11. Scollo A., Galli M.C., Contiero B., De Benedictis G.M., Orlandi B., Wicks N., Crouch S., Pearl C.A. (2013). Effects of Improvac and Bo- Gottardo F. (2021). Analgesia and/or anaesthesia during piglet priva on the testicular function of boars ten weeks after immuniza- castration – part II: practicability of farm protocols, resource ef- tion. Anim. Reprod. Sci., 142: 149–159. ficiency and economic implications. Ital. J. Anim. Sci., 20: 472– Zamaratskaia G., Rasmussen M.K. (2015). Immunocastration of male 478. pigs – situation today. Procedia Food Sci., 5: 324–327. Skade L., Kristensen C.S., Nielsen

excerpt 37

ia G., Rasmussen M.K. (2015). Immunocastration of male 478. pigs – situation today. Procedia Food Sci., 5: 324–327. Skade L., Kristensen C.S., Nielsen M.B.F., Diness L.H. (2021). Effect Zamaratskaia G., Babol J., Andersson H., Lundström K. (2004). of two methods and two anaesthetics for local anaesthesia of pig- Plasma skatole and androstenone levels in entire male pigs and lets during castration. Acta Vet. Scand., 63. relationship between boar taint compounds, sex steroids and thy- Škrlep M., Batorek Lukač N. (2023). Advantages and drawbacks of roxine at various ages. Livest. Prod. Sci., 87: 91–98. rearing entire male and immunocastrated pigs. Proc. 14th Interna- Zamaratskaia G., Babol J., Andersson H.K., Andersson K., Lundström tional Symposium Modern Trends in Livestock Production. K. (2005 a). Effect of live weight and dietary supplement of raw Škrlep M., Čandek-Potokar M., Lukač N.B., Povše M.P., Pugliese C., potato starch on the levels of skatole, androstenone, testosterone Labussičre E., Flores M. (2016). Comparison of entire male and and oestrone sulphate in entire male pigs. Livest. Prod. Sci., 93: immunocastrated pigs for dry-cured ham production under two 235–243. salting regimes. Meat Sci., 111: 27–37. Zamaratskaia G., Rydhmer L., Chen G., Madej A., Andersson H.K., Škrlep M., Tomašević I., Mörlein D., Novaković S., Egea M., Garrido Lundström K. (2005 b). Boar taint is related to endocrine and 210 A. Zalewska et al. anatomical changes at puberty but not to aggressive behaviour in Andersson K., Lundström K. (2008). Long-term effect of vaccina- entire male pigs. Reprod. Domest. Anim., 40: 500–506. tion against gonadotropin-releasing hormone, using Improvac™, Zamaratskaia G., Squires E.J., Babol J., Andersson H.K., Andersson on

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nim., 40: 500–506. tion against gonadotropin-releasing hormone, using Improvac™, Zamaratskaia G., Squires E.J., Babol J., Andersson H.K., Andersson on hormonal profile and behaviour of male pigs. Anim. Reprod. K., Lundström K. (2005 c). Relationship between the activities of Sci., 108: 37–48. cytochromes P4502E1 and P4502A6 and skatole content in fat in Zoels S., Reiter S., Ritzmann M., Weiß C., Numberger J., Schütz A., entire male pigs fed with and without raw potato starch. Livest. Lindner P., Weiler U. (2020). Influences of immunocastration on Prod. Sci., 95: 83–88. endocrine parameters, growth performance and carcass quality, as Zamaratskaia G., Chen G., Lundström K. (2006). Effects of sex, well as on boar taint and penile injuries. Animals, 10. weight, diet and hCG administration on levels of skatole and in- dole in the liver and hepatic activities of cytochromes P4502E1 and P4502A6 in pigs. Meat Sci., 72: 331–338. Received: 19 VIII 2024 Zamaratskaia G., Rydhmer L., Andersson H.K., Chen G., Lowagie S., Accepted: 2 IV 2025