Int’l - Castration in Pigs, implications of Boar taint in pork

Castration in pigs is not widely practiced in the UK and is prohibited under current Assured British Pigs Farm Assurance Standards. It is however standard practice in other parts of the EU and outside the EU. Issues relating to castration: • The most common technique for castration is surgical castration whereby the scrotum and membranes surrounding the testis are cut, the testis is removed from the scrotal sac and the vessels and structures travelling to the testis are severed by cutting, clamping or tearing. Few other common methods of castration such as elastic rubber bands or burdizzo ‘bloodless’ castrators can be used on the pig due to shape and position of the testes in the male. • There is substantial evidence that castration is painful and highly aversive to pigs and so is a significant welfare concern. The most painful part of castration appears to be the severing of the cords and vessels supplying testis. Fewer behavioural changes are seen in younger piglets after castration (2wks) than in older piglets (7wks) although both classes of piglets show pain related behaviour. An assumption is often made that the procedure is less traumatic to younger piglets although the contrary maybe true. • Studies have shown that the administration of local anaesthetic prior to castration can reduce the stress exhibited by piglets undergoing castration although the injection process itself will not be without discomfort. General anaesthesia with CO2 or halothane before castration will also reduce or ameliorate the pain of the procedure but the inhalation of these gases is known to be aversive to animals. The use of pain killers such as aspirin or butorphanol at the time of castration does not appear to effectively reduce pain. All these methods of anaesthesia or pain control will increase the costs of the procedure and are likely to significantly increase the time required, therefore reducing the chances of implementation. Reasons for castration: • It is widely reported that the meat from some entire male pigs has an unpleasant taint or odour – ‘boar taint’. Studies have been carried out to dispute the reduction in meat quality reportedly found in male pig meat and this has in large part been responsible for the lack of castration in the UK in addition to the costs saved in not carrying out the procedure. Certain countries and cultures however find boar taint a significant stumbling block to the use of uncastrated male pigs for meat production. • In common with other farmed species there may be benefits in terms of management and behaviour from castrating male pigs. Entire male pigs are more likely to fight and show aggressive and sexual behaviour, when kept with female pigs they will display sexual behaviour which may cause injuries and stress. There is evidence that female pigs kept in the presence of entire males will enter puberty earlier and so precipitate the problems of active sexual behaviour. Keeping male and female growing pigs separately can be difficult in some management systems. • Alternatives to painful physical castration could benefit both pig welfare and address the management and meat quality issues raised by uncastrated male pigs. One study has investigated the possibility of using a hormone (GnRH) to suppress the production of male hormones from the testes and so the compounds which cause boar taint and ‘male’ behaviour. A potentially more promising product is in use in Australia and New Zealand, ‘Improvac’ (CSL Animal Health) is a vaccine which stimulates the male pig’s immune system to make antibodies against its own male tissues. The testis therefore does not develop and the compounds causing boar taint are not produced. Because the product is a vaccine it is not present in the pigs at the time of slaughter and should not pose any threat to human health. The manufacturers claim that the product has no genetically modified ingredients; can reduce the incidence of PSE; improve the colour of the meat; increase marbling fat in the meat and therefore succulence and flavour; improve the growth rate of pigs; reduce the injuries and stress associated with aggression and sexual behaviours and improve the manageability of pigs. • ‘Improvac’ is not currently licensed for use in the EU or the UK although this may happen in time provided the product can meet the safety, quality and efficacy levels required by legislation. Consumer trials in Australia seem to show evidence that consumers prefer the pig meat from pigs treated with the product and are happy with the concept of a vaccine replacing physical castration.