ARTICLES
Immunocastration and its effects on carcass and meat traits of male pigs
Imunocastração e seus efeitos nas características de carcaça e carne de suínos machos
Immunocastration and its effects on carcass and meat traits of male pigs
Semina: Ciências Agrárias, vol. 39, no. 6, pp. 2531-2540, 2018
Universidade Estadual de Londrina
Received: 10 August 2017
Accepted: 13 September 2018
Abstract: To compose the experiment, 160 male Topgen pigs - 80 surgically castrated (treatment 1) and 80 immunocastrated (treatment 2) - were randomly selected from a commercial swine farm at the moment of slaughter. Surgical castration was performed when the animals were seven days of age and immunocastration was performed by administering two doses (2 mL each) of immunocastration vaccine (analogue of GnRF linked to a carrier protein, development of anti-GnRF antibodies, 200 mg of a GnRF-protein conjugate/mL) when they were 104 and 132 days of age. Animals from both treatments were maintained in masonry stalls, where they received water and ad libitum diet (the same feed for both groups). The animals were slaughtered at 160 days of age, and the length and width of the testicles of immunocastrated animals were evaluated, along with the degree and number of carcass lesions, carcass traits and meat quality of both treatments. The means of these measurements were calculated and compared by Student´s t-test. For the immunocastrated treatment, Pearson´s correlation coefficients were also calculated for testicle length and width with backfat thickness. Approximately 80% of the immunocastrated animals had testicle widths of 11 cm or less. Immunocastrated animals showed higher degrees of lesions, pH (initial and 8 hours), hue, muscle depth and loin eye area and lower brightness, redness, chroma and backfat thickness than the surgically castrated animals. The correlation between testicle length and width with backfat thickness was inverse. Immunocastration can be an alternative to improve the proportion of lean meat (longissimus thoracis) instead of fat (backfat thickness) leading to better carcass and meat quality, since fat has become undesirable from a nutritional point of view in swine.
Key words: Backfat thickness, Color, Gonadotropin-hormone, Improvac®, Testicle size.
Resumo: Para compor o experimento, 160 suínos machos (Topgen) - 80 castrados cirurgicamente (tratamento 1) e 80 imunocastrados (tratamento 2) - foram selecionados aleatoriamente de uma granja comercial de suínos no momento do abate. A castração cirúrgica foi realizada quando os animais tinham sete dias de idade e a imunocastração realizada através da administração de duas doses (2 mL cada) da vacina de imunocastração (análogo do GnRH ligado a uma proteína carreadora, desenvolvimento de anticorpos anti-GnRH, 200 mg de um conjugado de proteína GnRH/mL) quando os animais tinham 104 e 132 dias de idade. Os animais de ambos os tratamentos foram mantidos em baias de alvenaria, onde receberam água e ração ad libitum (a mesma dieta para ambos os grupos). Os animais foram abatidos com 160 dias de idade e foram avaliados o comprimento e largura dos testículos dos animais imunocastrados, e o grau e número de lesões na carcaça, características de carcaça e qualidade da carne de ambos os tratamentos. As médias para essas avaliações foram calculadas e comparadas com o teste t. Para o tratamento imunocastrado foi também calculado o coeficiente de correlação de Pearson´s do comprimento e largura dos testículos com a espessura de gordura. Aproximadamente 80% dos animais tiveram largura dos testículos igual ou menor que 11 cm. Os animais imunocastrados mostraram maior grau de lesão, pH (inicial e 8 horas), tonalidade, profundidade de músculo e área de olho de lombo e menor luminosidade, intensidade de vermelho, croma e espessura de gordura do que os animais castrados cirurgicamente. A correlação entre comprimento e largura dos testículos com a espessura de gordura foi negativa. A imunocastração pode ser uma alternativa para aumentar a proporção de carne magra (longissimus thoracis) em detrimento de gordura (espessura de gordura), levando a uma carcaça de melhor qualidade desde que a gordura suína se tornou indesejável do ponto de vista nutricional.
Palavras-chave: Cor, Espessura de gordura, Hormônio liberador de gonadotropinas, Vivax®, Tamanho dos testículos.
Introduction
Consumer preferences, behaviour and perception of meat depend not only on the appearance and sensory properties of the meat but also on psychological and marketing aspects (FONT-I-FURNOLS; GUERRERO, 2014). Many factors can affect the quality of meat, including the gender of the animal, which is an important determinant of muscle growth (LAWRIE; LEDWARD, 2006).
Pig production can be impaired by boar taint, which decreases pork quality due to a sensory defect. The sensory defect is caused by two compounds, skatole and androstenone, which are responsible for releasing an unpleasant odour and flavour when the meat or fat of entire male pigs are heated (TUYTTENS et al., 2011; ZAMARATSKAIA; SQUIRES, 2009). For this reason, according to the Inspection Regulations of the Industrial and Sanitary Use of Animal Products, as stated in Article 121 of Decree 30691 of March 29, 1952, in Brazil “It is forbidden to kill non-castrated pigs or animals showing signs of recent castration” (BRASIL, 1952). Because of this, surgical castration of males has been routinely performed to eliminate the possibility of odour in the meat. However, this method is not entirely satisfactory, as it has been associated with endangering pig health and welfare. Therefore, the development of methods that exclude conventional castration is desirable (LUNDSTRÖM; ZAMARATSKAIA, 2006).
Immunocastration is a method that immunizes the male piglet against gonadotropin-releasing hormone (GnRF). GnRF is a neuropeptide that is released from the hypothalamus to stimulate the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), which controls the production of testicular steroids. Immunological blocking of the signal from GnRF decreases the production of LH and testicular steroids (RYDHMER et al., 2010). As a consequence, immunization temporarily suppresses testicular development and function (TUYTTENS et al., 2011), avoiding boar taint, as well as being able to reduce pork eating quality fail rates by approximately 10%, when compared to entire male pigs (MOORE et al., 2017). Immunocastrated pigs, after applying the second dose of the vaccine, become calmer and exhibit significantly fewer aggressive and sexual behaviours (BAUMGARTNER et al., 2010), improving their welfare and carcass quality and reducing the incidence of skin lesions (ŠKRLEP et al., 2014).
As a non-invasive and practically painless method, not only does immunocastration improve animal welfare (DUNSHEA et al., 2005), but it also achieves some productive benefits, such as better growth rate, which is found in entire males before immunocastration, and better feed conversion ratio (FÀBREGA et al., 2010; RYDHMER et al., 2010). In addition to the superior performance, immunocastrated pigs can deposit a higher percentage of muscle and a lower percentage of fat compared to surgically castrated pigs (JANJIC et al., 2017; SANTOS et al., 2012).
However, when using immunocastration, economic factors such as the cost of the immunization vaccine, labour in the application and the possibility of costs in controlling the effectiveness of the vaccine in the slaughter line should be considered (PRUNIER et al., 2006).
The aim of this study was to evaluate carcass traits and pork meat quality of pigs that were submitted to an immunocastration process.
Material and Methods
The work was approved by the Ethics Committee on Animal Use of the State University of Londrina under Case No. 11888.2012.76.
Animals and treatments
To compose the experiment, 160 male Topgen pigs - 80 surgically castrated (treatment 1) and 80 immunocastrated (treatment 2) - were randomly selected from a commercial swine farm at the moment of slaughter. Surgical castration was performed when the animals were seven days of age. The scrotal method was used, in which an incision was made on each testicle, followed by exteriorization and removal. Immunocastration was performed by administering two doses (2 mL each) of an immunocastration vaccine (analogue of GnRF linked to a carrier protein, development of anti-GnRF antibodies, 200 mg of a GnRF-protein conjugate/mL). The first dose was injected at 104 days of age and the second dose at 132 days of age. Animals from both treatments were maintained in masonry stalls at a density of 0.90 m2 per animal, with nipple-type drinkers and troughs for feed, where they received water and ad libitum diet (the same feed for both groups) as recommended by the NRC (1998).
Slaughter
When the animals reached 160 days of age, they were slaughtered in a commercial abattoir under the Federal Inspection Service, in Joaquim Távora, Paraná, Brazil. During pre-slaughter management, the feed was removed 12 hours before shipment. Water was made available until slaughter. The pigs were stunned and exsanguinated according to Humane Slaughter Standards (BRASIL, 2000).
Testicle, carcass and meat analysis
The animals were identified according to treatment. The testicles length and width were measured with a tape measure of immunocastrated animals as required by BRASIL (2007) during their slaughter.
Subsequently, the degree and number of lesions on carcasses were determined for both treatments, wherein the degree of lesion was categorized according to a photographic standard of five categories: (1) not damaged; (2) lightly damaged; (3) slightly damaged; (4) moderately damaged; and (5) severely damaged (MLC, 1985). The number of lesions was quantified at three locations on the carcass: front, dorsal, and rear. These were classified according to the following: (1) lesion found in just one place on the carcass; (2) lesions found in two places on the carcass; (3) lesions found in three places on the carcass.
All carcasses were weighed 45 minutes and 12 hours after the beginning of the slaughter and the hot carcass weight (HCW) and the chilled carcass weight (CCW) were obtained, respectively. The pH of the longissimus dorsi muscle was determined on the left halves of the carcasses at 45 minutes (pH initial) and 8 hours (pH 8 h) after the beginning of the slaughter between the penultimate to the last rib, using a digital potentiometer (Testo 205®).
The left halves of the carcasses were sawn between the penultimate and the last rib, and 30 minutes later, using a portable colorimeter (CR-10, Kônica Minolta) the longissimus dorsi color components were evaluated: L* (luminosity), a* (redness) and b* (yellowness) by the CIELAB system. Chroma (c*) and hue (h*) were calculated using the values of a* and b* (CIELAB, 1978). In the exposed area, the muscle depth and backfat thickness were also measured using a digital caliper. The loin eye area was also estimated by drawing it on greaseproof paper and the obtained image was used to estimate the area in square centimeters, using a standard point counting method (AMSA, 2001).
Statistical analysis
The experimental design was completely randomized. The means of the treatments (surgically castrated and immunocastrated animals) were calculated and compared by Student´s t-test. For the immunocastrated treatment, Pearson´s correlation coefficients of the testicle length and width with backfat thickness were also calculated, both using the SAEG statistical program.
Results and Discussion
Testicle measurements of immunocastrated pigs
The maximum, minimum and average overall lengths of the testicles of immunocastrated animals were 25.0 cm, 11.0 cm and 15.03 cm, respectively, and the widths were 17.0 cm, 8.0 cm, and 10.36 cm, respectively (Table 1).
Maximum - maximum value observed; minimum - minimum value observed; general average - overall average presented.
In Brazil, the guidelines set by Decision Nº. 005/2007/CGI/DIPOA determine the procedures adopted by the Federal Inspection Service (FIS) in pig abattoirs regarding the slaughter of immunocastrated male pigs. One of the procedures adopted is the measurement of testicle width because male pigs with testicular widths greater than 11 cm may present a higher risk of boar taint, so these animals must be subjected to a cooking test before being release to commercial marketing, as recommended by Circular Nº. 069/88/DICAR/DIPOA of June 20, 1988 (BRASIL, 2007). However, a new Circular Nº. 001/2017/CGI-DIPOA/DIPOA/DIPOA-SDA/SDA/MAPA was launched in January 27, 2017 that replaces the previous one, and according to the new circular, studies have shown that the immunocastration vaccine has the expect effect, despite the testicle size being superior to 11 cm, which was stipulated in previous law (BRASIL, 2017). An explanation for the substitution of previous law (2007) by the current one (2017) is due to the superior slaughter weight observed now compared to 2007, also leading to superior testicle size because the immunocastration vaccine does not regress testicle size, it only suppresses development, invalidating the previous legislation.
In the current study, 80% of the immunocastrated animals evaluated had testicle widths lower or equal to 11 cm, which indicated that according to BRASIL (2007) these animals were within the standards required for marketing when they were slaughtered. Therefore, 20% of these animals were not within the recommended standards and showed testicles sizes of more than 11 cm. This does not mean that all 20% had boar taint (undesirable for market). However, in order to check the absence of boar taint, they were subjected to a cooking test by the abattoir before marketing; those that did not present boar taint were sent to market and consumers.
It is likely that the differences found between immunocastrated animals in testicle size is due to variation in immunological response to the vaccine, which, according to Einarsson (2006), is because of individual variance to antibody titres between different animals. In other words, it is possible that a few vaccinated male pigs did not respond equally to immunocastration, continuing with high concentrations of steroids, leading to the 20% of animals not meeting recommended standards (greater than 11 cm). The individual variation shown by the animals can be explained by several factors, mainly genetic, but also by the nutritional status, age and stress at the time of vaccination (TIZARD, 2014; GASPAR; SANTOS, 2016).
Carcass lesion degree
Carcass lesion degree was different between the treatments; however, the number of lesions was not different (P > 0.05). The lesion degree was higher (P ≤ 0.01) for the immunocastrated pigs than for the surgically castrated pigs (Table 2). As show in Figure 1, immunocastrated animals had lower percentages of degrees 1 and 2 (13% and 37% of degrees 1 and 2, respectively) than the surgically castrated animals (29% and 50% of degrees 1 and 2, respectively). However, the opposite trend was observed with degrees 3 and 4, where the immunocastrated pigs achieved approximately 45% and 5%, respectively, whereas the surgically castrated animals had values of 18% and 3%. No severely damaged carcasses (degree 5) were observed.
** Significant at 1% probability (P ≤ 0.01);* significant at 5% probability (P ≤ 0.05); NS - not significant (P > 0.05);1 SEM - standard error of the mean.
Figure 1
Percentage of lesions degree observed in surgically castrated and immunocastrated treatments.
(1) not damaged; (2) lightly damaged; (3) slightly damaged; (4) moderately damaged; (5) severely damaged.
It was expected that the immunocastrated treatment would have higher percentages of lesions on their carcasses than the surgically castrated treatment, since before receiving the second application of the immunocastration vaccine, the pigs are more aggressive than surgically castrated males (ALBRECHT et al., 2012) because they still have an entire male behaviour due to testosterone, leading to a higher number of agonistic interactions and a higher degree of skin lesions (BÜNGER et al., 2015). According to Einarsson (2006), it is only after the second dose of immunocastration vaccine that aggressive and sexual behaviours decrease. Therefore, it is likely that animals from Immunocastrated treatment in the current study behaved as non-castrated males before receiving the second immunization, resulting in injuries that were observed on their skins at slaughter.
Carcass and meat traits
There were no differences (P > 0.05) for hot carcass weight and chilled carcass weight between immunocastrated and surgically castrated animals. However, differences (P ≤ 0.05) were observed between them for pH initial, pH 8 h and all colour components, except for the yellowness (b*) value (Table 2). Longissimus thoracis pH values and hue (h*) were greater, while brightness (L*), redness (a*) and chroma (c*) were lower for immunocastrated animals than surgically castrated animals.
The result showed that hot carcass weight and chilled carcass weight are similar as the values reported by Pauly et al. (2009), who also found no differences between surgically castrated and immunocastrated pigs for these variables. However, the data found in the current study indicates that the meat from surgically castrated animals was clearer (higher L*) than that from immunocastrated animals, this is possibly due to increased extravasations of liquids and pigments, which is a consequence of meat with lower pH values (JONSÄLL et al., 2001). Jeong et al. (2011) also compared surgically castrated and immunocastrated pigs and found clearer meat in the surgically castrated pigs. However, these data are contrary to those observed in previous studies, in which Gispert et al. (2010) and Martinez-Macipe et al. (2016) did not report differences for L*, a* and b* between castrated and immunocastrated pigs.
For muscle depth, backfat thickness and loin eye area, there were differences (P ≤ 0.05) between immunocastrated and surgically castrated animals (Table 2). Muscle depth and loin eye area were higher and backfat thickness was lower for immunocastrated pigs than for surgically castrated pigs. The lower backfat thickness and the greater muscle depth and loin eye area found for immunocastrated animals can be attributed to the presence of steroids prior to immunization, whereas surgical castration eliminates such a possibility. According to Needham and Hoffman (2015), immunocastrated animals grow similarly to entire males until their booster vaccination, leading to a higher potential for anabolic growth than surgically castrated animals. Therefore, the results found in the current study were expected, because it is known that immunocastrated pigs have better feed conversions and higher potential to develop lean meat (LUNDSTRÖM; ZAMARATSKAIA, 2006), while surgical castration increases fat deposition since the male hormones involved in stimulating muscle growth are no longer present (NEEDHAM, 2014).
The reports of this study differed from those found by Martinez-Macipe et al. (2016), who did not observe differences in fat thickness and loin length between immunocastrated and surgically castrated animals. However, our results are in agreement with those reported by Aluwé et al. (2013) who observed higher (P < 0.001) backfat thickness in surgically castrated (17.7 mm) animals than in immunocastrated (14.2 mm) animals.
Correlation
There was moderate inverse correlation (P ≤ 0.01) between testicle length with backfat thickness and a null inverse correlation between testicle widths with backfat thickness. As the testicle length and width increased there was a decrease in backfat thickness (Table 3).
** Significant at 1% probability (P ≤ 0.01);* significant at 5% probability (P ≤ 0.05); NS - not significant (P > 0.05).
The negative correlations between testicle length and width with backfat thickness in immunocastrated pigs were expected, since the increase in the size of testicles is a consequence of testosterone levels (EINARSSON et al., 2011), which leads to a decrease in fat deposition. Therefore, in the current study, at the point when testicle size increased there was a decrease in backfat thickness.
Conclusion
Immunocastration performed with a vaccine can be an alternative to avoid surgical castration and to provide a leaner carcass, due to an increase of longissimus thoracis muscle and a decrease in backfat thickness. This is a relevant result, since fat has lately become undesirable from a nutritional point of view for many consumers. However, immunocastrated pigs lead to carcasses with higher degrees of lesions. Therefore, further research should be conducted to investigate the effect of immunocastration on pig behaviour.
Acknowledgment
The first author gratefully acknowledges the International Program CAPES (Brazilian Federal Agency) for the receipt of the scholarship of sandwich doctorate, developed at UC Davis University, California, USA.
References
ALBRECHT, A. K.; BEILAGE, E. G.; KANITZ, E.; PUPPE, B. ;TRAULSEN, I.; KRIETER, J. Influence of immunisation against GnRF on agonistic and mounting behaviour, serum testosterone concentration and body weight in male pigs compared with boars and barrows. Applied Animal Behaviour Science, Amsterdam, v. 138, n. 1-2, p. 28-35, 2012.
ALUWÉ, M.; LANGENDRIES, K. C. M.; BEKAERT, K. M.; TUYTTENS, F. A. M.; BRABANDER, D. L.; SMET, S.; MILLET, S. Effect of surgical castration, immunocastration and chicory-diet on the meat quality and palatability of boars. Meat Science, Amsterdam, v. 94, n. 3, p. 402-407, 2013.
AMERICAN MEAT SCIENCE ASSOCIATION - AMSA. Meat evaluation handbook. Savoy: AMSA, 2001.
BAUMGARTNER, J.; LAISTER, S.; KOLLER, M.; PFÜTZNER, A.; GRODZYCKI, M.; ANDREWS, S.; SCHMOLL, F. The behaviour of male fattening pigs following either surgical castration or vaccination with a GnRF vaccine. Applied Animal Behaviour Science, Amsterdam, v. 124, n. 1-2, p. 28-34, 2010.
BRASIL. Decreto, nº 30.691, de 29 de março de 1952. Aprova o novo regulamento da inspeção industrial e sanitária de produtos de origem animal. Brasília: Ministério da Agricultura, Pecuária e Abastecimento, 1952. 212 p.
______. Informação Diversa nº 061, de 23 de abril de 2007. Autorização para abate de suínos imunocastrados. Brasília: Ministério da Agricultura, Pecuária e Abastecimento, 2007. 3 p.
______. Instrução Normativa nº 3, de 17 de janeiro de 2000. Regulamento técnico de métodos de insensibilização para o abate humanitário de animais de açougue. Brasília: Ministério da Agricultura, Pecuária e Abastecimento, 2000. 5 p.
______. Memorando-Circular nº 1, de 27 de janeiro de 2017. Condições a serem observadas para o abate de suídeos submetidos a castração imunológica. Brasília: Ministério da Agricultura, Pecuária e Abastecimento, 2017. 2 p.
BÜNGER, B.; SCHRADER, L.; SCHRADE, H.; ZACHARIAS, B. Agonistic behaviour, skin lesions and activity pattern of entire male, female and castrated male finishing pigs. Applied Animal Behaviour Science, Amsterdam, v. 171, n. 1, p. 64-68, 2015.
DUNSHEA, F. R. ; D'SOUZA, D. N.; PETHICK, D. W.; HARPER, G. S.; WARNER, R. D. Effects of dietary factors and other metabolic modifiers on quality and nutritional value of meat. Meat Science, Amsterdam, v. 71, n. 1, p. 8-38, 2005.
EINARSSON, S. Vaccination against GnRH : pros and cons. Acta Veterinaria Scandinavica, Gardermoen, v. 48, n. 1, p. 1-4, 2006.
EINARSSON, S.; BRUNIUS, C.; WALLGREN, M.; LUNDSTRÖM, K.; ANDERSSON, K.; ZAMARATSKAIA, G.; RODRIGUEZ-MARTINEZ, H. Effects of early vaccination with Improvac?? on the development and function of reproductive organs of male pigs. Animal Reproduction Science, Manchester, v. 127, n. 1-2, p. 50-55, 2011.
FÀBREGA, E.; VELARDE, A.; CROS, J.; GISPERT, M.; SUÁREZ, P.; TIBAU, J.; SOLER, J. Effect of vaccination against gonadotrophin-releasing hormone, using Improvac®, on growth performance, body composition, behaviour and acute phase proteins. Livestock Science, Amsterdam, v. 132, n. 1-3, p. 53-59, 2010.
FONT-I-FURNOLS, M.; GUERRERO, L. Consumer preference, behavior and perception about meat and meat products: an overview. Meat Science, Amsterdam, v. 98, n. 3, p. 361-371, 2014.
GASPAR, E. B.; SANTOS, L. R. A vacinação de bovinos e o potencial de proteção dos animais. Campo Grande: EMBRAPA Gado de Corte, 2016. Disponível em: <https://www.embrapa.br/busca-de-noticias/-/noticia/14333015/artigo-a-vacinacao-de-bovinos-e-o-potencial-de-protecao-dos-animais>. Acesso em: 25 ago 2018.
GISPERT, M.; ÀNGELS OLIVER, M.; VELARDE, A.; SUAREZ, P.; PÉREZ, J.; FONT I FURNOLS, M. Carcass and meat quality characteristics of immunocastrated male, surgically castrated male, entire male and female pigs. Meat Science, Amsterdam, v. 85, n. 4, p. 664-670, 2010.
INTERNATIONAL COMISSION ON ILLUMINATION - CIELAB. Recommendations on uniform color spaces, color differences equations, psychometric color terms. 2th ed. Paris: CIE, 1978.
JANJIC, J.; CIRIC, J. I.; ALEKSIC, J.; GLAMOCLIJA, N.; STARCEVIC, M.; RADOVANOVIC, A.; BALTIC, M. Z. The effects of immunocastration on male pig yield parameters and meat quality. Meat Technology, Belgrade, v. 58, n. 1, p. 1-9, 2017.
JEONG, J.-Y.; CHOI, J.-H.; CHOI, Y.-S.; HAN, D.-J.; KIM, H.-Y.; LEE, M.-A.; LEE, D.-H.; KIM, C.-J. The effects of immunocastration on meat quality and sensory properties of pork bellies. Korean Journal for Food Science of Animal Resources, Seul, v. 31, n. 3, p. 372-380, 2011.
JONSÄLL, A.; JOHANSSON, L.; LUNDSTRÖM, K. Sensory quality and cooking loss of ham muscle (M. biceps femoris) from pigs reared indoors and outdoors. Meat Science, Amsterdam, v. 57, n. 3, p. 245-250, 2001.
LAWRIE, R. A.; LEDWARD, D. A. Lawrie's meat science. 7th ed. Abington: Woodhead Publishing Limited, 2006. 464 p.
LUNDSTRÖM, K.; ZAMARATSKAIA, G. Moving towards taint-free pork-alternatives to surgical castration. Acta Veterinaria Scandinavica, Gardermoen, v. 48, n. 1, p. 361-371, 2006.
MARTINEZ-MACIPE, M.; RODRIGUEZ, P.; IZQUIERDO, M.; GISPERT, M.; MANTECA, X.; MAINAU, E.; HERNANDEZ, F. I.; CLARET, A.; GUERRERO, L.; DALMAU, A. Comparison of meat quality parameters in surgical castrated versus vaccinated against gonadotrophin-releasing factor male and female Iberian pigs reared in free-ranging conditions. Meat Science, Amsterdam, v. 111, n. 1, p. 116-121, 2016.
MEAT AND LIVESTOCK COMMISSION - MLC. Concern at ringside damage in pigs. In: Meat and marketing technical notes. Milton Keynes: MLC, 1985.
MOORE, K. L.; MULLAN, B. P.; DUNSHEA, F. R. Boar taint, meat quality and fail rate in entire male pigs and male pigs immunized against gonadotrophin releasing factor as related to body weight and feeding regime. Meat Science, Amsterdam, v. 125, n. 1, p. 95-101, 2017.
NATIONAL RESEARCH COUNCIL - NRC. Nutrient requirement of swine. 10th ed. Washington: National Academy Press, 1998.
NEEDHAM, T. Effects of immunocastration on the nutrient responses, carcass traits and meat quality of growing pigs (Sus scrofa domesticus). 2014. Thesis (Master of Science in Animal Science) - Stellenbosch University, Stellenbosch, Republic of South Africa.
NEEDHAM, T.; HOFFMAN, L. C. Physical meat quality and chemical composition of the Longissimus thoracis of entire and immunocastrated pigs fed varying dietary protein levels with and without ractopamine hydrochloride. Meat Science, Amsterdam, v. 110, n.1, p. 101-108, 2015.
PAULY, C.; SPRING, P. ; O'DOHERTY, J. V.; AMPUERO KRAGTEN, S.; BEE, G. 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, Cambridge, v. 3, n. 7, p. 1057-1066, 2009.
PRUNIER, A.; BONNEAU, M.; VON BORELL, E. H.; CINOTTI, S.; GUNN, M.; FREDRIKSEN, B.; GIERSING, M.; MORTON, D. B.; TUYTTENS, F. A. M.; VELARDE, A. A review of the welfare consequences of surgical castration in piglets and the evaluation of non-surgical methods. Animal Welfare, Wheathampstead, v. 15, n. 1, p. 277-289, 2006.
RYDHMER, L.; LUNDSTRÖM, K.; ANDERSSON, K. Immunocastration reduces aggressive and sexual behaviour in male pigs. Animal, Cambridge, v. 4, n. 6, p. 965-972, 2010.
SANTOS, A. P.; KIEFER, C.; MARTINS, L. P.; FANTINI, C. C. Restrição alimentar para suínos machos castrados e imunocastrados em terminação. Ciência Rural, Santa Maria, v. 42, n. 1, p. 147-153, 2012.
ŠKRLEP, M. ; BATOREK-LUKAČ, N.; PREVOLNIK-POVŠE, M. ; ČANDEK-POTOKAR, M. Teoretical and practical aspects of immunocastration. Stočarstvo, Zagreb, v. 68, n. 2, p. 39-49, 2014.
TIZARD, I. R. Imunologia veterinária. Tradução: MEDINA, L.; LUCHESE, M. 9th ed. Rio de Janeiro: Elsevier, 2014. 568 p.
TUYTTENS, F. A. M.; VANHONACKER, F.; LANGENDRIES, K.; ALUWÉ, M.; MILLET, S.; BEKAERT, K.; VERBEKE, W. Effect of information provisioning on attitude toward surgical castration of male piglets and alternative strategies for avoiding boar taint. Research in Veterinary Science, Oxford, v. 91, n. 1, p. 327-332, 2011.
ZAMARATSKAIA, G.; SQUIRES, E. J. Biochemical, nutritional and genetic effects on boar taint in entire male pigs. Animal, Cambridge, v. 3, n. 11, p. 1508-1521, 2009.
Author notes
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