Animal Welfare Aspects of Preventing Boar Taint

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Acta Veterinaria Scandinavica BioMed Central Oral presentation Open Access Animal Welfare Aspects of Preventing Boar Taint Mette Giersing*, Jan Ladewig and Björn Forkman Address: Royal Veterinary and Agricultural University, Denmark * Corresponding author from Prevention of Boar Taint in Pig Production: The 19th Symposium of the Nordic Committee for Veterinary Scientific Cooperation Gardermoen, Norway. 21–22 November 2005 Published: 7 August 2006 <supplement> <title> <p>Prevention of Boar Taint in Pig Production: The 19th Symposium of the Nordic Committee for Veterinary Scientific Cooperation</p> </title> <note>Meeting abstracts</note> <url>http://www.biomedcentral.com/content/files/pdf/1751-0147-48-S1-full.pdf</url> </supplement> Acta Veterinaria Scandinavica 2006, 48(Suppl 1):S3 doi:10.1186/1751-0147-48-S1-S3 © 2006 Giersing et al.; licensee BioMed Central Ltd. Introduction Surgical castration Since boar taint is connected to testicular hormones and Surgical castration without anaesthesia is painful, as sexual maturity, surgical castration has for centuries been shown by the acute physiological responses (increased the method employed to prevent taint in meat from male Hypothalamic-Pituitary-Adrenal-responses and protein c- pigs, as well as to obtain more docile pigs. However, since fos expression in spinal neurons), as well as by vocalisa- the castration is performed without anaesthesia, it is pain- tion and behaviour during and immediately after the ful for the pig and therefore poses a serious welfare prob- operation. The frequency and duration of high-frequency lem. With growing focus on animal welfare in animal calls points towards the extraction of the testes and the production, surgical castration without anaesthesia and severing of the spermatic cords as

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l calls points towards the extraction of the testes and the production, surgical castration without anaesthesia and severing of the spermatic cords as being the most painful some form of analgesia is now increasingly regarded as in the procedure. Behavioural changes include disturbed unacceptable. massaging/suckling, activity, play and behavioural syn- chronisation. Some behavioural changes may persist for The options, singly or combined, are: more than 24 hours after the operation, e.g. tail-wagging and rump-scratching, behaviours that may be related to - castrating the pigs by methods that do not entail suffer- wound-healing. It appears that the assumption, that pigs ing, either surgically or non-surgically under the age of 7 days experience castration as less pain- ful than older pigs, is not substantiated. The incomplete - raising entire male pigs by methods that limit the devel- neural development of young animals may render them opment of boar taint more, rather than less, sensitive to painful stimuli. - selecting pigs with low levels of taint The effect of surgical castration on immune response var- ies with the type of challenge, with the age at castration, - producing only female pigs for consumption. and is modified by the use of anaesthesia [4]. The different results are, however, open to interpretation in terms of pig This presentation focuses on the animal welfare concerns welfare. of these different ways of preventing or reducing boar taint. Reports that castration compromises the health of the pigs in that the prevalence of pneumonia and other diseases The welfare aspects of castration have recently been was higher in castrates compared to gilts, and castrates reviewed by a working group under European Food Safety compared to boars and gilts, are not

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n was higher in castrates compared to gilts, and castrates reviewed by a working group under European Food Safety compared to boars and gilts, are not confirmed by a Authority [1], by Bonneau & Prunier [2] and by Prunier et review of data from Danish abattoirs. Here the opposite al.[3]. We wish to acknowledge the many involved was found with regard to Mycoplasma hyopneumoniae authors, as these reviews provide a significant basis and infection, with boars having the highest risk, females the the references for this presentation – supplemented by ref- lowest and castrates intermediate [5]. erences that have since come to light. Page 1 of 3 (page number not for citation purposes) Acta Veterinaria Scandinavica 2006, 48(Suppl 1):S3 Possible long-term effects on disease susceptibility need Another method of non-surgical castration is local further investigation – with regard to effects of the castra- destruction of testicular tissue by chemical compounds tion procedure as well as the absence of male steroids. such as formaldehyde, acetic acid, or salt from silver or zinc. No thorough welfare evaluation has been made. Local anaesthesia (commonly lidocaine plus adrenalin in Swelling of the testes or scrotum has been observed which a pH-buffered vehicle) effectively reduces the pain and indicates inflammation and, although not proven, is stress symptoms of castration- most effectively when likely to cause pain. injected both into the testes and in the funicular area of the scrotum [1]. This happens in spite of the additional The use of exogenous steroid hormones or steroid ago- handling involved, as the response to intratesticular injec- nists, to down-regulate the HPG axis, is not a method tion is much lower than to castration without anaesthesia. which would be acceptable

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ular injec- nists, to down-regulate the HPG axis, is not a method tion is much lower than to castration without anaesthesia. which would be acceptable to EU-consumers. Prunier [6] recently confirmed the effect of anaesthesia, but found no further effect of pre-emptive analgesia with Raising entire male pigs flunixine. Producing entire males for meat consumption calls for particular management procedures to minimise boar taint General anaesthesia of piglets, both injection and inhala- and to promote pig welfare. The one main boar taint sub- tion, has been regarded as unrealistic (time, cost and stance, skatole, can to a large extent be controlled by feed- forced veterinary assistance) under practical conditions. It ing and by keeping the pigs clean. The latter may lead to has moreover been associated with high piglet mortality extensive use of slatted floors, which is not conducive to as well as risks in the post-operative period of sedation. pig welfare. An alternative, and more welfare friendly Although CO2 inhalation has been regarded as too averse approach, is to control the climatic environment and pro- to pigs, new research indicates that CO2 anaesthesia, in vide pigs with possibilities for thermoregulation, e.g. the right gas proportions and with the right equipment, showers, instead of leaving them to wallow in their own may be effective and practicable at farm level [7]. The excreta. To reduce skatole development it is moreover rec- whole procedure is very fast: 15 seconds to unconscious- ommended that feed be withheld from entire males from ness, 1–2 minutes to total anaesthesia, 15 seconds for cas- 26 hours before slaughter. This may be a welfare problem, tration and 30–40 seconds for full recovery. Anaesthetic as as modern pigs have large appetites, but

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before slaughter. This may be a welfare problem, tration and 30–40 seconds for full recovery. Anaesthetic as as modern pigs have large appetites, but the harm to the well as analgesic properties of the procedure are under fur- welfare this might cause has not been investigated. ther investigation, as is the significance of the pig's initial aversion responses to the gas in relation to welfare. How- The remainder of this section is devoted to effects of – and ever, more recent results concerning anæsthesia of piglets on – androstenone. prior to castration are discussed in another paper of this volume. Entire males are more aggressive than females and cas- trates – this applies also to play fighting behaviour in Non-surgical castration young pigs. Both aggression/fighting and sexual behav- Methods of non-surgical castration include immunocas- iour/mounting which takes place in groups with male tration, by which male pigs are actively immunised pigs, compromise animal welfare as well as meat and car- against GnRH, thus inhibiting testicular development. cass quality through skin damage and leg injuries. Currently this method is used in Australia and New Zea- Recently, agonistic behaviour at feeding and sexual land. When effective, the behaviour, production and boar (mounting) behaviour was found to be significantly taint level of the immunocastrates are similar to surgically higher in entire male groups and mixed male and female castrated pigs. The procedure must be repeated twice to be groups compared to females alone [9]. In earlier studies effective, which means twice capture, restraint and injec- [1] it has been shown that boars in mixed sex groups had tion of relatively large pigs because, in order to retain the higher fat androstenone levels and were more

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en shown that boars in mixed sex groups had tion of relatively large pigs because, in order to retain the higher fat androstenone levels and were more sexually production advantages of entire males, the pigs are immu- mature than those in single sex groups when slaughtered nocastrated as late as possible (14 and 18 weeks of age). at over 100 kg live weight. Stress or trauma from capture, restraint and injection could probably be minimised by correct handling proce- Dominance and aggression are related to increased levels dures. Lesions in the hypothalamus, the target site of the of androstenone, with dominant animals having the high- vaccine, were initially reported, but a subsequent report est levels. High level of androstenone in a group has an by the same group of scientists concludes that immunisa- enhancing effect on androstenone levels of that group. tion against GnRH does not induce either morphological Salmon [10] found the highest level of aggression, sexual or pathological abnormalities in the brain [8]. The welfare (mounting) behaviour and the highest testes weight in a consequences of this vaccination still need further investi- male-only environment, compared to rooms with both gation. male and female groups, which could confirm that strong Page 2 of 3 (page number not for citation purposes) Acta Veterinaria Scandinavica 2006, 48(Suppl 1):S3 boar pheromone odour has a stimulating effect on other Food Safety Authority 2004 [http://www.efsa.eu.int/science/ahaw/ ahaw_opinions/512_en.html]. Accessed Sept 28 2005 boars. This is perhaps not surprising, considering that 2. Bonneau M, Prunier A: Alternatives to piglet castration. 56th boars in nature live in bachelor groups when reaching sex- Annual Meeting of the EAAP, Uppsala. June 5–8,2005 Session 27 ual

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o piglet castration. 56th boars in nature live in bachelor groups when reaching sex- Annual Meeting of the EAAP, Uppsala. June 5–8,2005 Session 27 ual maturity. Aggressive behaviour as well as sexual (PNPh5.1) . 3. Prunier A, Bonneau M, von Borrell EH, Cinotti S, Gunn M, Fredriksen behaviour has been shown to be associated with increases B, Giersing M, Morton DB, Tuyttens F, Velarde A: A review of the in testosterone and androstenone levels in plasma, welfare consequences of surgical castration in piglets and whereas corresponding increases in fat levels have only evaluation of non-surgical methods. Animal Welfare in press. 4. Merlot E, Prunier : A Long term consequences of castration on been measured after HCG challenge. the inflammatory response in piglets. Meeting of the Working Group on the Utilisation of Meat from Entire Male Pigs, Uppsala, June 8– 9,2005 . Mixing unacquainted pigs will always lead to aggression/ 5. Nielsen JP, Jensen SC, Bækbo P, Jorsal SE, Sørensen V, Houe H: Myc- fighting until a new dominance order has been estab- oplasma hyopneumoniae infection. A review of pathogene- lished. Mixing entire males will therefore not only be sis, diagnosis, risk factors and biological effects as input for economical modelling. CEPROS report no.5. Research Centre for the stressful and injurious, but increase the risk of higher Management of Animal Production and Health, Foulum, Denmark 2000. androstenone levels. 'Birth to slaughter' systems, where 6. Prunier A, Moriez R, Mounier AM: Effects of local anaesthesia and preemptive analgesia on plasma profiles of cortisol and litters of pigs are kept together from birth to slaughter, ACTH in piglets undergoing surgical castration. Meeting of the including transport and preslaughter lairage, not only Working Group

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irth to slaughter, ACTH in piglets undergoing surgical castration. Meeting of the including transport and preslaughter lairage, not only Working Group on the Utilisation of Meat from Entire Male Pigs, Uppsala, minimises skin damage (fighting), but also reduces the June 8–9,2005 . 7. Svendsen O, Strøbech L, Forkman B: CO2/O2 as an anaesthetic level of androstenone in entire males [11]. Whether litter agent during castration of piglets. Meeting of the Working Group rearing and minimal mixing influences the development on the Utilisation of Meat from Entire Male Pigs, Uppsala, June 8–9 2005 . of sexual maturity and mounting behaviour is not yet 8. Oonk HA, Turkstra JA, Schaaper WMM, Meloen RH: Further expe- rience with anti-GnRH vaccines in male pigs. Proc. EAAP Work- clear. It is likely that mixing of strangers and establish- ing Group on Production and Utilisation of Meat from Entire Male Pigs. ment of new hierarchies will provoke testicular activity Milton Keynes, U.K. September 27–29 1995 . 9. Boyle L, Björklund L: Effects of finishing entire males in single and accelerate the initiation of puberty, whereas the initi- or mixed sex groups and split marketing on behaviour, wel- ation of puberty may be inhibited in stable sibling groups fare and performance. 3rd Int. Workshop: Assessment of Animal Welfare at Farm and Group Level (WAFL-05) Sept. 22–24, 2005 Vienna. Abstract . Because of increased aggressiveness and activity levels, it is 10. Salmon L: The effects of gender separation on behaviour and likely that rearing environments and handling facilities performance of entire boars and gilts from 60 kg to 130 kg for entire males should contain more resources (space, live weight. Meeting of the Working Group on the Utilisation of Meat from Entire Male Pigs,

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kg for entire males should contain more resources (space, live weight. Meeting of the Working Group on the Utilisation of Meat from Entire Male Pigs, Uppsala, June 8–9, 2005 . facilities, including devices for thermoregulatory behav- 11. Fredriksen B, Nafstad O, Lium BM, Marka CH, Heier BT, Dahl E, iour) than normally provided for castrates in order to Choinski JU: Entire male pigs in a farrow-to-finish-system. Effects on androstenone and skatole. Livestock Science in press. minimise competition and aggression. If adequate facili- ties are not given, effects of behaviour on skin and leg injuries, as well as the general stress level, may be increased if pigs cannot escape or avoid harassment from particularly active males. Effects of these factors on boar taint are not documented. High levels of received aggres- sion or levels of cortisol have not been associated with either skatole or androstenone levels. Genetic selection It is not known whether selecting or breeding animals for low skatole and androstenone production or for high ska- tole and androstenone metabolism has any consequences for animal welfare, but this seems unlikely. Publish with Bio Med Central and every scientist can read your work free of charge Sperm sorting "BioMed Central will be the most significant development for The current technique for sperm sorting in pigs, in order disseminating the results of biomedical researc h in our lifetime." to produce only female pigs for meat consumption, neces- Sir Paul Nurse, Cancer Research UK sitates intrauterine insemination of the sows, which could Your research papers will be: increase the risk of discomfort, injury and pain and thus available free of charge to the entire biomedical community compromise the welfare of the sows. This may change with the

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ort, injury and pain and thus available free of charge to the entire biomedical community compromise the welfare of the sows. This may change with the development of new techniques. peer reviewed and published immediately upon acceptance cited in PubMed and archived on PubMed Central References yours — you keep the copyright 1. EFSA: Welfare Aspects of the Castration of Piglets. Scientific Submit your manuscript here: BioMedcentral Report of the Scientific Panel for Animal Health and Welfare, European http://www.biomedcentral.com/info/publishing_adv.asp Page 3 of 3 (page number not for citation purposes)