Behavior and handling of physically and immunologically castrated market pigs on farm and going to market

Physical castration is a common management practice on commercial swine farms in the United States to reduce the incidence of boar taint and aggressive behavior. One alternative to physical castration (PC) is to immunologically castrate (IC) male pigs by blocking the gonadotropin-releasing factor (GnRF), thereby reducing levels of LH, FSH, testosterone, and androstenone. The objectives of this study were to evaluate the effects of IC on pig behavior, human-pig interactions, and handling during and after transport. Pigs were given the first immunization at wk 7 of the growerfinisher period, and second immunizations were given at wk 11, 13, or 14 of the grower-finisher period. Behaviors of PC and IC barrows were sampled at 3 time points after entering finishing at 9 wk of age: 7 wk before first injection, 16 wk (after immunization was complete) into finishing, and 1 d before marketing (16 to 19 wk into finishing). Handling during loading and unloading of trailers going to market was also quantified. Before the first injection, intact males showed increased aggression (P = 0.014) and mounting (P = 0.048), whereas PC barrows spent more (P = 0.003) time feeding than intact males. There were treatment × time interactions for lying (P = 0.018), aggression (P < 0.001), and standing (P = 0.009) behaviors. Few differences were observed in pig-human interactions between PC and IC barrows, with IC and PC approaching people in the same amount of time, but IC barrows were more (P < 0.001) aggressive in chewing and rubbing on the test person's pant leg and boots. When handling and loading for processing in the home barn, PC barrows were more (P < 0.05) vocal than IC barrows. Fewer dead and down pigs were observed among IC (0%) compared with PC barrows (1.17%). Immunological castration may result in similar or improved animal welfare compared to the stress of physical castration without pain relief.