Modern farming industry faces a large scale and highly intensive rearing conditions, in which the goal is to maximize the production efficiency. Moreover, environmental issues including global warming and disease outbreak are another challenge that could add stressors affecting domestic animal health, both psychological and physical well-being.Major stressors in domestic animals include nutritional factors (unbalanced nutrients, toxins, and diet changes), environmental factors (quality of air and water, temperature, dust, and humidity,), biological factors (weaning, infection, castration, and injury), and physical factors (transportation, lack of spacious area, and social status). These stressors cause growth retardation coincident with modulation of immune system, especially in the gastrointestinal tract. It is rather obvious that deficiency in nutrients causes immune function impairment, which can be reversed by nutrient repletion. Nutritional deficiencies in animals with infectious diseases are the main contributor to a high morbidity and mortality.In my talk, I will focus on some of stressors in relation to host immune responses in major domestic animals using in vitro and in vivo model systems. Furthermore, toxins and/or microbial metabolites in the presence and absence of antigenic stimulation causing destruction of tight junctions and intestinal epithelial cells will be discussed. The audience will gain insight on the action mechanism of (1) stress and modulation of host immune responses, (2) vaccine and adjuvants, and (3) nutritional balance, microbiota and immune modulation in domestic animals.