Do mood disorders play a role in pig welfare?

The work examines the hypothesis that the behavioural disorders found in pigs under conditions of stress may also be attributable to inherent conditions of alteration in mood. In light of new evidence that links the biochemical characterization of human depression to a particular profile of fatty acids in platelets, in particular the Palmitic Acid, Linoleic and Arachidonic, the decision was made to investigate platelet fatty acids of different animal species (pig, cattle, cat, sheep), together with the same data found in literature for rats and guinea pigs. The results obtained from normal and depressed human subjects have made it possible to achieve a particular Artificial Neural Network called the Self Organizing Map (SOM). This network, which is also used in the classification of some species (pigs, cattle, cats and sheep), has been utilised to distribute and classify all the animals studied, in agreement with the fatty acid markers of depressive disorder and the degree of saturation of membrane lipids. In agreement with this approach, the pig is comparable to humans that present a clinical diagnosis of depression. A critical analysis of specific references indicates the existence of a wide range of similarities between human beings suffering from depression and pigs. All the results we obtained on platelets, together with bibliographic evidence make plausible, in our view, the hypothesis that the pig is an animal intrinsically prone to depression. This tendency, which is probably genetically predetermined, must be taken into account in studies on the welfare of this animal and could also serve as a good model for the study of antidepressant molecules for humans.