Vocal responses of piglets to castration: identifying procedural sources of pain

The aims of this study were to identify which aspects of castration are pai nful to piglets, and to determine if less painful methods are available. Pr evious work has shown that piglets produce more high frequency calls (>1 kH z) when castrated than when handled identically but not castrated, or when castrated using a local anesthetic. In Experiment 1, we used 90 piglets to assess the vocal responses to different components of the castration proced ure: restraint, washing the ano-genital region, scrotal incision, and pulli ng/severing of the spermatic cords. Compared to sham-operated animals (whic h were restrained and washed but not castrated) incision of the scrotum pro duced much more high-frequency calling than restraint alone at the same sta ge of the procedure. Pulling and severing the spermatic cords evoked the gr eatest amount of calling, significantly more than the incision, regardless of the order in which the incision and pull/sever were performed (P<0.001). In Experiment 2 (49 piglets), we found no difference in calling between tw o methods routinely used to sever the spermatic cord: cutting the cord with a scalpel versus tearing the cord by pulling on the testicle. These findin gs suggest that the pulling and severing of the spermatic cords are the mos t painful components of castration, yet altering the method of severing res ulted in no change in call. rate. Rather than focusing on pain control, wel fare problems associated with castration may be better reduced by using non -surgical approaches, or by eliminating the need for castration in the firs t place. (C) 2000 Elsevier Science B.V. All rights reserved.