Date Published: June 24, 2019
Publisher: Public Library of Science
Author(s): Maria Cristina Yunes, Dayane L. Teixeira, Marina A. G. von Keyserlingk, Maria J. Hötzel, I Anna S Olsson.
Male piglets are commonly castrated to eliminate the risk of boar taint. Surgical castration is the commonly used procedure and is known to induce pain. Gene modification targeted at eliminating boar taint in male pigs has been proposed as a possible alternative to surgical castration. The aims of this study were to explore public acceptability of this biotechnology using a mixed methods approach. Quantitative data to assess acceptability of 570 participants from southern Brazil were analysed with multinomial logistic regression models and Spearman correlations; qualitative responses of the reasons provided in support of their position were coded into themes. Just over half of the participants (56%) considered gene modification of male pigs acceptable. Acceptability was lower among participants who grew up in an agricultural environment (ρ = 0.02), but was not influenced by sex, age, religion, urban or rural living, or level of education. Acceptability of gene modification of male pigs as an alternative to surgical castration was positively related to the perception of benefits (r = -0.56, ρ<0.0001) and negatively related to the participant’s perception of risks (r = -0.35, ρ<0.0001). Acceptability was not related to knowledge of basic concepts of genetic biotechnologies (r = 0.06, ρ<0.14), or to awareness of issues related to pig castration or boar taint (r = 0.03, ρ<0.44), both of which were low among participants. Participants that considered gene modification of pigs acceptable justified their position using arguments that it improved animal welfare. In contrast, those that were not in favour were generally opposed to genetic modification. Unforeseen downstream consequences of using genetic modification in this manner was a major concern raised by over 80% of participants. Our findings suggest that perceived animal welfare may encourage public support of gene editing of food animals. However, potential risks of the technology need to be addressed and conveyed to the public, as many participants requested clarification of such risks as a condition for support.
Meat of male pigs that have not been castrated may present an odour and flavour called boar taint, caused by substances that accumulate in the fat (i.e. androstenone and skatole), that many consumers find repulsive [1–3]. To avoid boar taint, most piglets are surgically castrated soon after birth, a known painful procedure; however, pain control measures during and after the procedure are available [4, 5], but not routinely used . An alternative to surgical castration is immunocastration, which is done through a vaccine that induces the production of antibodies against GnRH that inhibits testicular development and function; thereby, reducing fat androstenone concentrations to levels below the reported threshold for human sensory detection [5, 7]. Another option is the production of entire males with acceptable levels of boar taint, through a combination of early slaughter and specific feeding and environmental measures . This option, however, is restricted to some European countries  and, in Brazil, the slaughter of uncastrated male pigs is prohibited . Many producers also consider alternative measures to surgical castration or the use of pain control costly, impractical or ineffective [6, 10, 11].
This study was approved by the Ethics Committee on Experimentation of the Santa Catarina State University (P. 2.280.893).
Demographic data are shown in Table 1. Participants’ distribution of sex, age (except for those 66 years old and over), and place of residency approximately corresponded to the Brazilian population according to the Brazilian Institute of Geography and Statistics Census  for the three southern states of Brazil. Compared to the general population of the southern region of Brazil, a higher proportion of participants had undergraduate level education and self-identified as not being religious .
Just over half of the participants found the scenario of gene edited male pigs to prevent boar taint acceptable. In general, acceptance was justified by perceived improvements in animal welfare; rejection, in contrast, was related to opposition to genetic modification and perceived loss of naturalness. Equally important, however, was that acceptance was often conditional either directly or indirectly, with participants stating that they desired: 1) assurance that unforeseen harm to humans, animals and the environment would be prevented, and 2) greater clarification of the process and its consequences.
The participants surveyed in this study placed great value on the potential animal welfare benefits arising from gene editing to remove boar taint in pigs, citing this as their primary reason for supporting this practice. However, this support was not unconditional but rather was accompanied by responses that users of these types of technologies must be clear, honest and transparent in their communications regarding the unknown downstream risks associated with the technology. Perceived risks and uncertainty may be more determinant of public attitudes towards gene editing of farm animals, particularly in the case of applications that do not involve improvement in animal welfare.