Castration in male pigs: techniques and animal welfare issues

Castration in male pigs is usually performed during the first weeks of life without prior anesthesia. This technique, however, is known to induce acute pain and stress and will therefore not be tolerated any longer by animal welfare organizations. Practical and animal-friendly alternatives to surgical castration are the production of entire male pigs, semen sexing or immunological castration. Fattening boars has the benefits of better feed efficiency, higher lean meat yield and increased animal welfare due to no pain and stress of castration. The most important disadvantage in raising entire male pigs is the incidence of boar taint ranging between 10 and 75%. To identify tainted carcasses an accurate and rapid on-line method for detection of odorous compounds is absolutely necessary. Sperm sexing through flow cytometry is the only commercially available method at the moment but speed of separation is too low for practical application. Active immunization of boars against gonadotropin-releasing-hormone (GnRH) at the end of the fattening period results in a significant reduction of testicular weight and androstenone production while the benefits of daily growth gain, meat quality as well as welfare remain the same as in entire males. In the present review more detailed information is given about the various techniques, especially the practical application of immunocastration on a large scale base.