IMMUNOCASTRATION IN PIGS

Abstract

There is a strong initiative in the European Union to stop physical castration of piglets as practiced today and alternatives have been proposed. Among them immune castration; it consists of two vaccinations against gonadotropin releasing hormone (GnRH) and uses the natural immune system of pig for the achievement of castration-like effect. It seems an acceptable alternative to physical castration because it offers a solution for boar taint problem avoiding pain and also aggressive behaviour that is seen when rearing entire males (EM). Moreover, physiological effects of immunocastration are not expressed until seven days after revaccination (V2), usually performed 4-6 weeks preceding slaughter, which allows benefiting from feed efficiency and lean tissue growth of EM through most of the growing-finishing period. However, after V2 a substantial increase in average daily feed intake is observed in immunocastrated pigs (IC) resulting in a progressive decrease in feed efficiency and an increase in body fatness of IC in comparison to EM. Although the vaccine producer recommends an interval of 4 weeks between V2 and slaughter, recent studies indicated that a shorter or longer delay could be considered. Regarding the effectiveness of immunisation, it should be noted that some animals do not react to it, thus there is a need of a fast, simple but effective method for boar taint detection on the slaughter line. The paper gives an overview of immunocastration effects on boar taint, body composition, meat quality, with an emphasis on feeding strategies, advantages and disadvantages of this alternative.

Full text

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015
IMMUNOCASTRATION IN PIGS
M. Čandek-Potokar1,2, N. Batorek Lukač1, E. Labussière3
1 Agricultural Institute of Slovenia, Hacquetovaulica 17, SI-1000 Ljubljana, Slovenia
2 University of Maribor, Faculty of Agriculture and Life Sciences, Pivola 10, SI-2311 Hoče, Slovenia
3 INRA, UMR 1348 Pegase, F-35590 Saint-Gilles, France andAgrocampus-Ouest, UMR 1348 Pegase,
F-35000 Rennes, France
Corresponding author: meta.candek-potokar@kis.si
Invited paper
Abstract: There is a strong initiative in the European Union to stop
physical castration of piglets as practiced today and alternatives have been
proposed. Among them immune castration; it consists of two vaccinations against
gonadotropin releasing hormone (GnRH) and uses the natural immune system of
pig for the achievement of castration-like effect. It seems an acceptable alternative
to physical castration because it offers a solution for boar taint problem avoiding
pain and also aggressive behaviour that is seen when rearing entire males (EM).
Moreover, physiological effects of immunocastration are not expressed until seven
days after revaccination (V2), usually performed 4-6 weeks preceding slaughter,
which allows benefiting from feed efficiency and lean tissue growth of EM through
most of the growing-finishing period. However, after V2 a substantial increase in
average daily feed intake is observed in immunocastrated pigs (IC) resulting in a
progressive decrease in feed efficiency and an increase in body fatness of IC in
comparison to EM. Although the vaccine producer recommends an interval of 4
weeks between V2 and slaughter, recent studies indicated that a shorter or longer
delay could be considered. Regarding the effectiveness of immunisation, it should
be noted that some animals do not react to it, thus there is a need of a fast, simple
but effective method for boar taint detection on the slaughter line. The paper gives
an overview of immunocastration effects on boar taint, body composition, meat
quality, with an emphasis on feeding strategies, advantages and disadvantages of
this alternative.
Key words: pig, immunocastration, performance, boar taint
Introduction
Castration of male piglets is a routine practice in pig husbandry with main
aim to avoid boar taint; it involves surgical procedure in which testes with
epididymides are physically removed from scrotal sack; and in EU countries it is
allowed to be performed without anaesthesia or analgesia during the first 7 days of

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
325
life (Council Directive, 2008). Castrated pigs are also calmer and fatter and express
less sexual behaviour in group housing (EFSA, 2004). Although generally used,
this procedure of castration has been criticized as being painful for the piglets
(McGlone et al., 1993; Prunier et al., 2006). It may be considered even
unnecessary in modern pig production, especially if pigs are raised for meat
consumption, where raising entire males (EM) would be more efficient (Bonneau,
1998;Trefan et al., 2013). Thus, for welfare and economic reasons a strong
initiative (http://boars2018.com) has been developed in the European Union
tovoluntary stop surgical castration as practiced nowadays until 2018 and thus a
need has emerged for new, alternative solutions for boar taint prevention. Intensive
research of alternatives to surgical castration, diagnostic methods for boar taint
detection, harmonization of analytical methods of substances responsible for boar
taint, and attitudes of stakeholders is being supported by the European Commission
(http://ec.europa.eu/food/animal/welfare/farm/initiativesen.htm; According to
current indications the most promising alternatives are immunocastration, surgical
castration with pain relief, rearing of EM, genetic selection on the reduced boar
taint and semen sorting technique with subsequent rearing of female offspring. The
latter two methods are sustainable and animal welfare friendly but long-term
alternatives, whereas the first three alternatives are suitable for immediate
introduction into practice. It seems that for fresh meat consumption rearing of
EMis the most interesting alternative, whereas immunocastration,a method that
will be discussed in the present review, remains a good alternative in the case of
fattening to a higher age and weight.
Immunocastration
Immunocastration uses natural immune system of the pig to produce
specific antibodies that bind and neutralise the gonadotropin releasing hormone
(GnRH) and by that, blocks the hypothalamic-pituitary-gonadal. It effectively
inhibits testis growth and sexual steroids synthesis (Hilbe et al., 2006; Fang et al.,
2010; Einarsson et al., 2011) and can be successfully used as an alternative to
physical castration of pigs (Dunshea et al., 2001). According to the manufacturer’s
instructions, the vaccine should be administered in two doses at least four weeks
apart. Although no withdrawal period is needed, it is recommended that the second
vaccination (V2) is performed four to six weeks before slaughter, in order to ensure
clearance of boar taint substances from adipose tissue. However, recent studies
demonstrated that a shorter (Lealiifano et al., 2011; Kubale et al., 2013) or longer
delay could be considered (Claus et al., 2008; Einarssonet al., 2009). At
commercial slaughter weights, levels of androstenone and skatole are below
sensory threshold already two weeks after V2 (Lealiifano et al., 2011; Kubale et

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
326
al., 2013) whereas the effect of immunocastration persists for at least 10 weeks
after V2 (Claus et al., 2008; Zamaratskaia et al., 2008; Einarsson et al., 2009).
This timing is important from the perspective of pig production. The shorter the
delay, the more benefit from the boar-like performance can be expected, whereas
fluctuations in the demand or other specific market needs could lead to a prolonged
delay and pig producers need to be sure that there is no risk of boar taint.
The effects of immunocastration on boar taint compounds
and reproductive organs
The results of recent meta-analysis (Batorek et al., 2012a) show that the
magnitude of the response in efficient immunocastration is by far the largest for
reproductive organs and boar taint substances. This has been shown in all studies,
despite the high heterogeneity between studies due to different vaccination
protocols used. In agreement with Brunius et al. (2011), the effects on reproductive
organs are larger for early vaccination than for late vaccination. The largest
reduction is observed for seminal vesicle weight (Bonneau, 2010; Batorek et al.,
2012a; Čandek-Potokar et al., 2014). This is related to their anatomical structure
of liquid-containing vesicles, which can be quickly resorbed, whereas the other
accessory glands and testes take more time to regress due to firmer structure. This
result supports the suggestion of Bonneau (2010) to use seminal vesicles as a
diagnostic tool to assess the success of immunocastration at slaughter. Consistent
with the regression of the reproductive tract, a loss of functional activity is
observed at a histological level (Falvo et al., 1986; Grizzle et al., 1987, Awoniyi et
al., 1988; Kubale et al., 2013). Immunocastration reduces the mean diameter of the
seminiferous tubules, the number of spermatogonia and spermatocytes, induces the
atrophy of the Leydig cells and reduces the weight of glandular tissues and
secretory products of accessory sexual glands (Kubale et al., 2013). However, the
intensity of changes occurring at a histological level is dependent on the time of
immunization (Einarsson et al., 2011; Kubale et al., 2013). The impairment of
testis functionality results in the prevention of the accumulation of boar taint
compounds in adipose tissue (Batorek et al., 2012a) ofimmunocastrated pigs (IC).
However, as shown in the above mentioned meta-analysis, slight differences
between IC and surgically castrated pigs (SC) for both substances remain and
could perhaps be due to the effectiveness of immunisation. Namely, it should be
noted that some animals do not react to the vaccine (so-called "non-responders")
due to poor immunological response or technically improper vaccination (Jaros et
al., 2005; Škrlep et al., 2012). The number of non-responders is relatively low (1-
3%) and is expected to be similar to the incidence of cryptorchidism. However, this

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
327
implies a need for simple but effective method for their detection at the slaughter
line.
The effects of immunocastration and different feeding
strategies on growth performance
Physiologically IC are similar to EM before V2, with no difference in
growth performance (Millet et al., 2011; Batorek et al., 2012a). However as
observed in meta-analysis (Batorek et al., 2012a), feed intake tends to be higher in
IC than in EM, which might be related to an early response to the vaccination in
some pigs, shown to have reduced luteinizing hormone (LH) and testosterone
levels already after the first vaccination (V1; Turkstra et al., 2002). The majority of
IC produces a sufficient quantity of antibodies to neutralize all secreted GnRH
shortly after V2. Consequently LH and steroid secretions are suppressed and the
metabolism adapts itself in approximately seven days after V2 (Claus et al., 2007).
The largest effect observed is a drastic increase in feed intake comparatively to EM
(for approximately 450 g/day; Millet et al., 2011; Batorek et al., 2012a; Dunshea
et al., 2013). This effect was related to the sharp reduction in the production of
androgens and oestrogens, known to decrease feed intake (Claus and Weiler,
1987), and to reduced socio-sexual behaviour in IC compared to EM (Cronin et al.,
2003). Likewise, feed intake of IC after V2 is slightly higher compared toSC (for
approximately 105 g/day; Batorek et al., 2012a; Millet et al., 2011; Dunshea et al.,
2013). A possible explanation resides in hormonal changes following V2 as well.
The absence of testicular steroids and the presence of relatively low amounts of
leptin in IC after V2 compared with SC (Batorek et al., 2012b) might cause high
feed intake in IC, because both oestrogens and leptin are known to reduce appetite
(Claus and Weiler, 1994; Barb et al., 1998). Together with the presence of higher
insulin-like growth factor I in ad libitum feed IC compared to SC (Claus et al.,
2007; Batorek et al., 2012b), which contributes to improved feed efficiency, the
increased feed intake stimulatesgrowth. Indeed, it was shown that the average daily
gain (ADG) of IC in the period following V2 is approximately 145 and 117 g/day
higher compared to SC and EM, respectively (Millet et al., 2011; Batorek et al.,
2012a; Dunshea et al., 2013). Eventually feed efficiency in IC following V2 is
improved compared to SC (for approximately 0.10 points; Millet et al., 2011;
Dunshea et al., 2013) but reduced compared to EM (for approximately 0.35 points;
Millet et al., 2011; Dunshea et al., 2013). It has also been shown that maintenance
metabolisable energy requirements of IC are intermediate between SC and EM
(Labussiere et al., 2013). Considering the whole fattening period (V1-slaughter) IC
are much more efficient than SC because physiologically they are EM before V2
and also some time after, however they are less efficient and slightly fatter than

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
328
EM because they are slaughtered after the transient period is finished, but they
exhibit moderately faster growth compared with both SC and EM (Batorek et al.,
2012a). These facts initiated the idea to study the effects of restricted feed
allowance of IC after V2 with the aim to improve feed efficiency and to avoid
increased fatness of the carcass of IC. In that regard, our results (Batorek et al.,
2012b) show that despite a slower growth of feed-restricted IC, feed efficiency is
improved and performance traits are similar to those in ad libitum fed EM. On the
contrary, Quiniou et al. (2012) suggest that feed restriction of IC pigs after V2 has
no practical interest, because restricting feed allowance to group-housed IC results
in slower growth with no improvement of feed efficiency. The discrepancy in the
results of the mentioned studies can perhaps be dueto different experimental
conditions in particular the housing system (individual vs. group). However, both
studies suggested that restrictive feeding of IC could increase aggressiveness as
higher incidence (comparable to EM)of lesions during fattening (Quiniou et al.,
2012) or prior to slaughter (Batorek et al., 2012b) was observed. This may perhaps
be due to chronic stress and higher excitability caused by feed restriction (D’Eathet
al., 2009) and, for that reason, might be questioned from a welfare point of view.
Reduced dietary energy content in feed by inclusion of fibre-rich ingredients
without limitation of feed allowance might be applied as an alternative.
The effects of immunocastration and different feeding
strategies on carcass composition and meat quality
The results of meta-analyses agree that IC have lower dressing percentage
than SC (for approximately 2.0%; Batorek et al., 2012a; Dunshea et al., 2013) and,
although not always significantly, also than EM (for approximately 0.3%; Batorek
et al., 2012a; Dunshea et al., 2013). Lower dressing percentage in IC has been
attributed to the presence of reproductive tract (Boler et al., 2012; Boler et al.,
2014), higher gut fill due to increased average feed intake (Dunshea et al., 2001;
Gispert et al., 2010; Boler et al., 2014), increased weight of abdominal fat (Škrlep
et al., 2010a; Škrlep et al., 2010b) and also to the heavier internal organs, namely
liver and kidneys (Pauly et al., 2008; Pauly et al., 2009; Boler et al., 2014).
Because physiologically immunocastration becomes effective in the last weeks
before slaughter, when the transient period after V2 is finished, IC take advantage
of boar like growth performance for most of growing-fattening period. Hence they
produce leaner carcasses compared to SC (lean content is increased for
approximately 1.0%; Pauly et al., 2009; Millet et al., 2011; Batorek et al., 2012a)
due to increased muscling and decreased fatness. According to Dunshea et al.
(2013) backfat thickness is approximately 2.64 mm lower in IC compared to SC,
but approximately 1.53 mm higher than in EM at slaughter. Latter can be attributed

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to high feed intake following V2 that enhances fat deposition and consequently
lowers lean content of the carcass in IC compared to EM (for approximately 1.5%;
Pauly et al., 2009; Millet et al., 2011; Batorek et al., 2012a). However, fat
deposition in IC largely depends on the timing of immunization - the length of
period between immunization and slaughter (Lealiifano et al., 2011) and possibly
feeding strategy applied. However, feed restriction in IC had either no significant
effect on fat deposition and carcass leanness (dos Santos et al., 2012; Quiniou et
al., 2012) or only reduced leaf fat weight (Batorek et al., 2012b). The lack of effect
of restricted feed allowance on carcass leanness in the above mentioned studies
might be related to a shorter duration of the applied restriction. In general, the
weight of the main carcass cuts of IC and EM seems similar, with exception of
heavier belly weight (Batorek et al., 2012a), which is consistent with the higher fat
content of the carcass. Whereas the heavier ham and shoulder weights and the
lighterbelly weight in IC compared with SC reported in meta-analysis (Batorek et
al., 2012a) can be ascribed to the fact that muscles of the fore and hind limbs
develop earlier in life than muscles of posture (e.g. loin, belly muscles) and may be
less affected by the reduced anabolic potential after immunocastration as discussed
by Pauly et al. (2009). The synthesis of published data on meat quality shows that
IC do not differ from SC (Batorek et al.,2012a; Pauly et al., 2012), whereas IC
present some advantages over EM, namely higher intramuscular fat content and
lower shear force (Batorek et al., 2012a; Pauly et al., 2012). Later might be
attributed to increased growth rate in the weeks prior to slaughter, resulting in
enhanced protein turn-over in vivo and increased proteolysis post-mortem
(Therkildsen et al., 2004; Lametsch et al., 2006). Although compensatory growth
has been proposed to have a positive effect on pork tenderness (Kristensen et al.,
2002), neither sensory tenderness nor juiciness were affected by castration method
or sex (Pauly et al., 2012; Trefan et al., 2013). Our meta-analysis also indicated
that IC might have some disadvantages in meat quality compared with EM
(Batorek et al., 2012a), including a higher drip loss, which is consistent with a
tendency for lower ultimate pH and higher CIE L (lightness) value. However this
was not confirmed by Pauly et al. (2009) and Trefan et al. (2013), with exception
of lighter meat colour (Trefan et al., 2013).
Conclusions
Physiologically the immunocastration becomes effective in a week
following V2, therefore in case of late revaccination during the month preceding
slaughter, growth characteristics of IC are similar to those of EM and better
production performance (i.e. growth rate, feed intake, feed efficiency and carcass
leanness) of IC compared with SC is observed. In regard to meat quality, IC are

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October 7 – 9, 2015.
330
more similar to SC than EM. Although the vaccine producer recommends that a
four-week interval between V2 and slaughter, recent studies indicated that a shorter
or longer delay could be considered. Regarding the effectiveness of immunization,
it should be noted that some animals do not react to it, and thus, there is a need of a
simple but effective method for their detection on the slaughter line.
Acknowledgment
The authors acknowledge the financial support of Slovenian Research
Agency (project L4-5521, program P4-0133 and PhD grant of Nina Batorek
Lukač).
Imunokastracija prasadi
M. Čandek-Potokar, N. Batorek Lukač, E. Labussière
Rezime
Postoji jaka inicijativa u Evropskoj uniji da se zaustavi fizička kastracija
prasadi kako se praktikuje danas i predložene su alternative. Među njima je
imunokastracija: sastoji se od dve vakcinacije protiv gonadotropin oslobađajućeg
hormona (GnRH) i koristi prirodni imuni sistem svinje za postizanje efekta
kastracije. Čini se prihvatljiva alternativa fizičkoj kastraciji jer nudi rešenje za
problem nepoželjnog polnog mirisa nerasta i izbega bol i agresivnog ponašanja
koje se vidi kada se gaje nekastrirani mužjaci (EM). Pored toga, fiziološki efekti
imunokastracije nisu izraženi do sedam dana nakon revakcinacije (V2), obično se
izvodi 4-6 nedelje pre klanja, što omogućava efikasnost u korišćenju hrane i rast
mišićnog tkiva kod EM tokom najvećeg dela perioda porasta-završni period.
Međutim, nakon V2 značajan porast prosečnog dnevnog unosa hrane je primećen
kod imunokastriranih svinja (IC) što rezultira progresivnim smanjenjem efikasnosti
hrane i povećanjem masnog tkiva u telu u odnosu na EM. Iako proizvođač vakcina
preporučuje interval od 4 nedelje između V2 i klanja, novije studije pokazuju da bi
kraće ili duže odlaganje/produženje ovog perioda moglo da se uzme u obzir. Što se
tiče efikasnosti imunizacije, treba napomenuti da neki životinje ne reaguju na nju,
tako da postoji potreba za brzim, jednostavnim ali efikasnim metodom za detekciju
polnog mirisa nerasta na liniji klanja. Rad daje pregled uticaja imunokastracije
svinja na polni miris nerasta, telesni sastav, kvalitet mesa, sa naglaskom na
strategije hranjenja, prednosti i nedostatke ove alternative.

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References
AWONIYI C.A., CHANDRASHEKAR V., ARTHUR R.D., SCHANBACHER
B.D., AMADOR A.G., FALVO R.E. (1988): Pituitary and Leydig cell function in
boars actively immunized against gonadotropin-releasing hormone. Journal of
Reproduction and Fertility, 84, 295-302.
BARB C.R., YAN X., AZIAN M.J., KRAELING R.R., RAMPACEK G.B.,
RAMSEY T.G. (1998): Recombinant porcine leptin reduces feed intake and
stimulates growth hormone secretion in swine. Domestic Animal Endocrinology,
15, 77-86.
BATOREK N., ČANDEK-POTOKAR M., BONNEAU M., VAN MILGEN J.
(2012a): Meta-analysis of the effect of immunocastration on production
performance, reproductive organs and boar taint compounds in pigs. Animal, 6, 8,
1330-1338.
BATOREK N., ŠKRLEP M., PRUNIER A., LOUVEAU I., NOBLET J.,
BONNEAU M., ČANDEK-POTOKAR M. (2012b): Effect of feed restriction on
hormones, performance, carcass traits, and meat quality in immunocastrated pigs.
Journal of Animal Science, 90, 4593-4603.
BOLER D.D., KILLEFER J., MEEUWSE D.M., KING V.L., MCKEITH F.K.,
DILGER A.C. (2012): Effects of slaughter time post-second injection on carcass
cutting yields and bacon characteristics of immunologically castrated male pigs.
Journal of Animal Science, 90, 334-344.
BOLER D.D., PULS C.L., CLARK D.L., ELLIS M., SCHROEDER A.L.,
MATZAT P.D., KILLEFER J., MCKEITH F.K., DILGER A.C. (2014): Effects of
immunological castration (Improvest®) on changes in dressing percentage and
carcass characteristics of finishing pigs. Journal of Animal Science, 91, 359–368.
BONNEAU M. (1998): Use of entire males for pig meat in the European Union.
Meat Science, 49, 257-272.
BONNEAU M. (2010): Accessory sex glands as a tool to measure the efficacy of
immunocastration in male pigs. Animal, 4, 930-932.
BRUNIUS C., ZAMARATSKAIA G., ANDERSSON K., CHEN G., NORRBY
M., MADEJ A., LUNDSTRÖM K. (2011). Early immunocastration of male pigs
with Improvac® – Effect on boar taint, hormones and reproductive organs. Vaccine,
29, 9514-9520.
ČANDEK-POTOKAR M., PREVOLNIK M., ŠKRLEP M. (2014): Testes weight
is not reliable tool for discriminating immunocastrates from entire males. V:
POPOVIĆ, Zoran (ur.). Proceedings of the International Symposium on Animal
Science 2014, 23-25th September 2014, Belgrade, Serbia. Belgrade Faculty of
Agriculture, 2014, str. 43-49.

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
332
CLAUS R., WEILER U. (1987): Umwelteinflüsse auf das
geschlechtsspezifischeWachstumsvermögen. ÜzT, 15, 301-316.
CLAUS R., WEILER U. (1994): Relationships between IGF-I, cortisol, and
osteocalcin in peripheral plasma of growing pigs. Experimental and Clinical
Endocrinology & Diabetes, 104, 344-349.
CLAUS R., LACORN M., DANOWSKI K., PEARCE M.C., BAUER A. (2007):
Short-term endocrine and metabolic reactions before and after second
immunization against GnRH in boars. Vaccine, 25, 4689-4696.
CLAUS R., ROTTNER S., RUECKERT C. (2008): Individual return to Leydig
cell function after GnRH-immunization of boars. Vaccine, 26, 4571-4578.
COUNCIL DIRECTIVE (2008): Council Directive 2008/120/EC of 18 December
2008 laying down minimum standards for the protection of pigs.
CRONIN G.M., DUNSHEA F.R., BUTLER K.L., MCCAULEY I., BARNETT
J.L., HEMSWORTH P.H. (2003): The effects of immuno- and surgical-castration
on the behaviour and consequently growth of group-housed, male finisher pigs.
Applied Animal Behaviour Science, 81, 111-126.
D’EATH R.B., TOLKAMP B.J., KYRIAZAKIS I., LAWRENCE A.B. (2009):
‘Freedom from hunger’ and preventing obesity: the animal welfare implications of
reducing food quantity or quality. Animal Behaviour, 77, 275-288.
DOS SANTOS A.P., KIEFER C., MARTINS L.P., FANTINI C.C. (2012): Feeding
restriction to finishing barrows and immunocastrated swine. Ciencia Rural, 42,
147-153.
DUNSHEA F.R., COLANTONI C., HOWARD K., MCCAULEY I., JACKSON
P., LONG K.A., LOPATICKI S., NUGENT E.A., SIMONS J.A., WALKER J.,
HENNESSY D.P. (2001): Vaccination of boars with a GnRH vaccine (Improvac)
eliminates boar taint and increases growth performance. Journal of Animal
Science, 79, 2524–2535.
DUNSHEA F.R., ALLISON J.R.D., BERTRAM M., BOLER D.D., BROSSARD
L., CAMPBELL R., CRANE J.P., HENNESSY D.P., HUBER L., DE LANGE C.,
FERGUSON N., MATZAT P., MCKEITH F., MORAES P.J.U., MULLAN B.P.,
NOBLET J., QUINIOU N., TOKACH M. (2013): The effect of immunization
against GnRF on nutrient requirements of male pigs: A review. Animal, 7, 1769-
1778.
EFSA (2004): Welfare Aspects of the Castration of Piglets. Scientific Report of the
Scientific Panel for Animal Health and Welfare, European Food Safety Authority
2004. EFSA Journal, 91, 1-19.
EINARSSON S., ANDERSSON K., WALLGREN M., LUNDSTRÖM K.,
RODRIGUEZ-MARTINEZ H. (2009): Short- and long-term effects of
immunization against gonadotropin-releasing hormone, using ImprovacTM, on

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
333
sexual maturity, reproductive organs and sperm morphology in male pigs.
Theriogenology, 71, 302-310.
EINARSSON S., BRUNIUS C., WALLGREN M., LUNDSTRÖM K.,
ANDERSSON K., ZAMARATSKAIA G., RODRIGUEZ-MARTINEZ H. (2011):
Effects of early vaccination with Improvac® on the development and function of
reproductive organs of male pigs. Animal Reproduction Science, 127, 50-55.
FALVO R.E., CHANDRASHEKAR V., ARTHUR R.D., KUENSTLER A.R.,
HASSON T., AWONIYI C., SCHANBACHER B.D. (1986): Effect of active
immunization against LHRH or LH in boars – reproductive consequences and
performance traits. Journal of Animal Science, 63, 986–994.
FANG F., LI H., LIU Y., ZHANG Y., TAO Y., LI Y., CAO H., WANG S.,
WANG L., ZHANG X. (2010):Active immunization with recombinant GnRH
fusion protein in boars reduces both testicular development and mRNA expression
levels of GnRH receptor in pituitary. Animal Reproduction Science, 119, 275-281.
GISPERT M., ÀNGELS OLIVER M., VELARDE A., SUAREZ P., PEREZ J.,
FONT I FURNOLS M. (2010): Carcass and meat quality characteristics of
immunocastrated male, surgically castrated male, entire male and female pigs.
Meat Science, 85, 664–670.
GRIZZLE T.B., ESBENSHADE K.L., JOHNSON B.H. (1987): Active
immunization of boars against gonadotropin releasing hormone. I. Effects on
reproductive parameters. Theriogenology, 27, 571-580.
HILBE M., JAROS P., EHRENSPERGER F., ZLINSZKY K., JANETT F.,
HÄSSING M., THUN R. (2006): Histomorphological and immunohistochemical
findings in testes, bulbourethral glands and brain of immunologically castrated
piglets. SchweizerArchivfürTierheilkunde, 148, 599-608.
JAROS P., BÜRGI E., STÄRK K.D.C., CLAUS R., HENNESSY D., THUN R.
(2005): Effect of immunization against GnRH on androstenone concentration,
growth performance and carcass quality in intact male pigs. Livestock Production
Science, 92, 31-38.
KRISTENSEN L., THERKILDSEN M., RIIS B.M., SORENSEN M.T.,
OKSBJERG N., PURSLOW P., ERTBJERG P. (2002): Dietary induced changes
of muscle growth rate in pigs: Effects on in vivo and post-mortem muscle
proteolysis and meat quality. Journal of Animal Science, 80, 2862–2871.
KUBALE V., BATOREK N., ŠKRLEP M., PRUNIER A., BONNEAU M.,
FAZARINC G., ČANDEK-POTOKAR M. (2013): Steroid hormones, boar taint
compounds, and reproductive organs in pigs according to the delay between
immunocastration and slaughter. Theriogenology, 79, 69-80.
LABUSSIÈRE E., DUBOIS S., VAN MILGEN J., NOBLET J. (2013):
Partitioning of heat production in growing pigs as a tool to improve the
determination of efficiency of energy utilization. Frontiers in Physiology, 4, 146.

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
334
LAMETSCH R., KRISTENSEN L., LARSEN M.R., THERKILDSEN M.,
OKSBJERG N., ERTBJERG P. (2006): Changes in the muscle proteome after
compensatory growth in pigs. Journal of Animal Science, 84, 918-924.
LEALIIFANO A.K., PLUSKE J.R., NICHOLLS R.R., DUNSHEA F.R.,
CAMPBELL R.G., HENNESSY D.P., MILLER D.W., HANSEN C.F., MULLAN
B.P. (2011): Reducing the length of time between harvest and the secondary
gonadotropin-releasing factor immunization improves growth performance and
clears boar taint compounds in male finishing pigs. Journal of Animal Science, 89,
2782-2792.
MCGLONE J.J., NICHOLSON R.I., HELLMAN J.M., HERZOG D.N. (1993):
The development of pain in young pigs associated with castration and attempts to
prevent castration-induced behavioural changes. Journal of Animal Science, 71,
1441-1446.
MILLET S., GIELKENS K., DE BRABANDER D., JANSSENS G.P.J. (2011):
Considerations on the performance of immunocastrated male pigs. Animal, 5,
1119-1123.
PAULY C., SPRING P., O’DOHERTY J.V., AMPUERO KRAGTEN S., BEE G.
(2008): Performances, meat quality and boar taint of castrates and entire male pigs
fed a standard and a raw potato starch-enriched diet. Animal, 2; 1707-1715.
PAULY C., SPRING P., O’DOHERTY J.V., AMPUERO KRAGTEN S., BEE G.
(2009): Growth performance, carcass characteristics and meat quality of group-
penned surgically castrated, immunocastrated (Improvac®) and entire male pigs
and individually penned entire male pigs. Animal, 3, 1057–1066.
PRUNIER A., BONNEAU M., VON BORELL E.H., CINOTTI S., GUNN M.,
FREDRIKSEN B., GIERSHING M., MORTON D.B., TUYTTENS F.A.M.,
VELARDE A. (2006): A review of welfare consequences of surgical castration in
piglets and the evaluation of non-surgical methods. Animal Welfare, 15, 277-289.
QUINIOU N., MONZIOLS M., COLIN F., GOUES T., COURBOULAY V.
(2012): Effect of feed restriction on the performance and behaviour of pigs
immunologically castrated with Improvac®. Animal, 6, 1420-1426.
ŠKRLEP M., BATOREK N., BONNEAU M., FAZARINC G., ŠEGULA B.,
ČANDEK-POTOKAR M. (2012): Elevated fat skatole levels in immunocastrated,
surgically castrated and entire male pigs with acute dysentery. Veterinary Journal,
194, 3, 417-419.
ŠKRLEP M., ŠEGULA B., ZAJEC M., KASTELIC M., KOŠOROK S.,
FAZARINC G., ČANDEK-POTOKAR M.(2010a): Effect of immunocastration
(Improvac®) in fattening pigs I: growth performance, reproductive organs and
malodorous compounds. Slovenian Veterinary Research, 47, 2, 57-64.
ŠKRLEP M., ŠEGULA B., PREVOLNIK M., KIRBIŠ A., FAZARINC G.,
ČANDEK-POTOKAR M. (2010b): Effect of immunocastration (Improvac®) in

Proceedings of the 4th International Congress
New Perspectives and Challenges of Sustainable Livestock Production
October 7 – 9, 2015.
335
fattening pigs II: Carcass traits and meat quality. Slovenian Veterinary Research,
47, 2, 65-72.
THERKILDSEN M., VESTERGAARD M., BUSK H., JENSEN M.T., RIIS B.,
KARLSSON A.H., KRISTENSEN L., ERTBJERG P., OKSBJERG N. (2004):
Compensatory growth in slaughter pigs - in vitro muscle protein turnover at
slaughter, circulating IGF-1, performance and carcass quality. Livestock
Production Science, 88, 63-75.
TREFAN L., DOESCHL-WILSON A., ROOKE J.A., TERLOUW C., BÜNGER
L. (2013): Meta-analysis of effects of gender in combination with carcass weight
and breed on pork quality. Journal of Animal Science, 91, 3, 1480-1492.
TURKSTRA J.A., VAN DIEPEN J.T.M., JONGBLOED A.W., OONK H.B., VAN
DE WIEL D.F.M., MELOEN R.H. (2002): Performance of male pigs immunized
against GnRH is related to the time of onset of biological response. Journal of
Animal Science, 80, 2953–2959.
ZAMARATSKAIA G., ANDERSSON H.K., CHEN G., ANDERSSON K.,
MADEJ A., LUNDSTRÖM K. (2008): Effect of a Gonadotropin-releasing
Hormone Vaccine (ImprovacTM) on Steroid Hormones, Boar Taint Compounds and
Performance in Entire Male Pigs. Reproduction in Domestic Animals, 43, 351–
359.