Knowledge about gene expression in animals involved in abnormal behaviors can contribute to understanding of the underlying biological mechanisms. The present study aimed to explore the motivational background to tail biting, an abnormal injurious behavior and severe welfare problem in pig production. Affymetrix microarrays were used to investigate gene expression differences in the hypothalamus and prefrontal cortex of pigs performing tail biting, pigs receiving bites to the tail and neutral pigs who were not involved in the behavior. In the hypothalamus, 32 transcripts were differentially expressed (P<0.05) when tail biters were compared with neutral pigs, 130 when comparing receiver pigs with neutrals, and two when tail biters were compared with receivers. In the prefrontal cortex, seven transcripts were differently expressed in tail biters compared to neutrals, seven in receivers vs. neutrals and none in the tail biters vs. receivers. In total 19 genes showed a different expression pattern in neutral pigs compared to both performers and receivers. This implies that the functions of these may provide knowledge about why the neutral pigs are not involved in tail biting behavior as performers or receivers. Among these 19 transcripts were genes associated with production traits in pigs (PDK4; Lan et al., 2009), sociality in humans and mice (GTF2I; Sakurai et al., 2011) and novelty seeking in humans (EGF; Keltikangas-Järvinen et al., 2006). These are in line with hypotheses linking tail biting with reduced back fat thickness (Breuer et al., 2005) and explorative behavior (EFSA, 2007). The study is from the Swedish University of Agricultural Sciences, Uppsala, Sweden.
Brunberg E, Jensen P, Isaksson A, Keeling LJ. Genes Brain Behav 2012 Nov 12 [Epub ahead of print].