Evaluation of growth, carcass traits and reproductive organs of young boars in response to zeranol implantation

A review of the welfare consequences of surgical castration in piglets and the evaluation of non-surgical methods

Male piglets are castrated primarily to prevent the unpleasant odours and flavours of entire male pig meat (boar-taint). Although castration can be legally performed without analgesia in the first seven days of life, available evidence shows that castration at any age is painful and may have a detrimental influence on health. Few anaesthetics or analgesics are licensed for use in piglets. The known methods for general and epidural anaesthesia cannot be run at the farm level for practical and/or legal reasons. Use of the local anaesthetic lidocaine is easy and allows the pain resulting from castration to be alleviated. Local destruction of testicular tissue by intra-testicular injection of chemical compounds (salts and acids) is an alternative to surgical castration but needs further investigation regarding welfare improvement and boar taint reduction. Immunocastration, by which castration is achieved using active immunisation (anti–GnRH immunisation) is an efficient alternative to surgical castration; however, there are no licensed vaccines in the EU and the consequences, in terms of pig welfare as well as its acceptability among EU consumers, need further evaluation.

Profiling of free and conjugated [3H]zeranol metabolites in pig plasma

Extraction and high-performance liquid chromatographic (HPLC) procedures are described that permit the complete analysis of free and conjugated zeranol metabolites in plasma from pigs implanted with [3H]zeranol. Free metabolites (9.0%) are extracted and then analysed by radio-HPLC on a reversed phase C18 column. They are distributed between three compounds that have been identified by gas chromatography-mass spectrometry as taleranol, zeranol and zeralanone. Direct radio-HPLC of the pre-extracted, deproteinated and Sep-Pak C18-purified plasma on a reversed-phase C18 column using tetrabutylammonium as an ion-pairing agent showed four main peaks: one corresponds to a weakly retained unidentified compound(s) (20%) and the other three were identified as the taleranol, zeranol and zeralanone glucuro conjugates. However, the total recovery is only about 25% owing to strong affinity of this polar material for the plasma proteins. Enzymatic deconjugation of the pre-extracted plasma followed by radio-HPLC analysis of the freed metabolites led to a good recovery of the radioactivity (81.8%) and allowed the quantitation of the different metabolites. These preliminary results indicate that zeranol is metabolized in the pig following pathways similar to those in other tested species.