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Evaluation of the behavioral differences between physically and immunologically castrated male pigs
The standard method of castration for swine in the United States is to physically remove the testes within the first month of life, typically without the use of anesthesia or analgesia. An alternative solution to this welfare issue is to use immunological castration. This pilot study was conducted to evaluate the behavioral differences between male pigs castrated physically by scalpel at less than 10 d of age or immunologically during the finishing period. The study was conducted on 31 male pigs housed in finishing pens from 11 weeks of age until 24 weeks of age. The 31 pigs were randomly assigned to three pens of eight and one pen of seven. Two pens were physically castrated (PHYSIC) while the other two were immunologically castrated (IMPRO), using a commercially available immunological product that was designed to suppress puberty in male swine (Improvest®, Zoetis, Florham Park, New Jersey). The first injection was administered on day one of the trial; four weeks later, a second injection was administered, both by a trained Zoetis employee. Eight weeks after the second injection, the pigs were sent to slaughter. Behavior was assessed using continuous 24 hour video surveillance that began on day one of the trial to correspond to the first injection date and repeated at weekly intervals for the duration of the trial. Scan sampling was used on all pigs in all pens at two minute intervals. Time budgets were recorded and analyzed for comparison between treatment groups and behavior sampling dates. Tukey’s tests within the MIXED procedure of SAS 9.3 (SAS Inst. Inc., Cary, NC) were used to analyze the effects of castration treatment, week on trial, and the interaction of castration treatment and week on trial. The number of pigs per pen was utilized as a weighting variable within the model. Of the behavioral parameters measured (laying, standing exclusively, sitting exclusively, walking, eating while standing, eating while sitting, drinking while standing, drinking while sitting, agonistic while standing, and agonistic while sitting) there were no significant differences between treatments (P > 0.05). There was a castration treatment by week on trial interaction effect on expression of mounting behavior. In weeks 2, 3, 5, and 7, IMPRO pigs showed significantly more mounting behavior compared to PHYSIC pigs (P = 0.0012). The results of this pilot study suggest that additional research is necessary to understand if behavioral implications exist for immunologically castrated swine.
Keywords: Swine, Castration, Behavior