Incorporating farm animal models for the study of neuropsychiatric diseases: Expansion of the possibilities

Neuropsychiatric disorders are highly prevalent but particularly difficult to study. Animal models have been developed to understand the pathogenesis of these diseases and to develop treatments; however, the translational value of these findings has been limited. We discuss rodent and nonhuman primate (NHP) models for neuropsychiatric disorders and suggest farm animal models (FAMs) as a supplement or where NHP availability is limited and the scientific question allows it, as an alternative when feasible (i.e., when sufficient knowledge and validated methods exist). We discuss how farm animals can be relevant based on their anatomical, physiological, and brain functional similarity to humans, well-documented genetics, and complex higher cognitive functions. We discuss limitations of FAMs, including less availability of validated tools, relative lack of historical data, less expertise among livestock producers and scientists, and relatively limited understanding of functional neurocircuitry compared to rodents and NHPs. We offer guidance on the use of farm animals in research and emphasize the possibility of conducting semi-experimental studies on farms or in slaughterhouses. We argue that sustainability of research is enhanced by the availability of farm animal brains from the slaughterhouse, and generalizability is increased by using naturalistic, spontaneously occurring disease models, including from veterinary populations. The comparative validity, practicality, and ethics of using FAMs is discussed. We advocate for expanded basic science research of farm animal brains and behaviors, and conclude that FAMs may be advantageous for several reasons, although ultimately, the research question and available tools must guide the best choice of model.