Host behavior, environment and ability to self-medicate

Herbivores form preferences for substances that raise fitness such as nutritious foods and avoid those substances, which lower fitness such as plant secondary compounds (PSC). Nevertheless, some PSC at certain concentrations have the potential to raise fitness as they act against infective diseases such as parasitism. The objective of the present review is to assess whether parasitized farm animals are able to manifest self-medicative behaviors. The ability of herbivores to self-select these medicinal plant compounds emerges from the inherent adaptive nature of behavioral responses in living organisms. In order to manifest self-medication animals should experience discomfort caused by a certain illness and also relief associated with the mitigation of sickness brought about by the ingestion of a medicinal plant. Observational and controlled studies suggest such conditions, as well as self-medicative behaviors occur not only in wild but also in domestic herbivores. Self-medicative behaviors may allow individuals seek medicinal plant products when infected by parasites, even at times when the manager is not aware of the existence of parasitism in the flock. Self-medication may also allow for proper nutrition as animals offered choices will consume PSC-containing plants as well as nutritious and safe forages. Management programs should be geared at enhancing in herbivores the likelihood of the association medicine-relief from sickness and at favoring the transmission of self-medicative behavior across generations.