Physical castration is a common management practice on commercial swine farms in the United States to reduce the incidence of boar taint and aggressive behaviour, reported K. Guay and colleagues at Texas Tech University in Journal of Animal Science.

One alternative to physical castration (PC), they say, 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 Lubbock study were to evaluate the effects of IC on pig behaviour, human-pig interactions and handling during and after transport.

Pigs were given the first immunisation in week 7 of the grower-finisher period, and second immunisations were given in weeks 11, 13 or 14 of the grower-finisher period.

Behaviour of PC and IC barrows was sampled at three time-points after entering finishing at nine weeks of age: seven weeks before the first injection, 16 weeks (after immunisation was complete) into finishing, and one day before marketing (16 to 19 weeks 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) behaviours.

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 (zero per cent) than with PC barrows (1.17 per cent).

Guay and colleagues concluded that immunological castration may result in similar or improved animal welfare compared to the stress of physical castration without pain relief.

Reference

Guay K., G. Salgado, G. Thompson, B. Backus, A. Sapkota, W. Chaya and J.J. McGlone. 2013. Behavior and handling of physically and immunologically castrated market pigs on farm and going to market. J Anim. Sci. 91(11):5410-5417. doi: 10.2527/jas.2012-5726

December 2013