Mycotoxins and biogenic amines are among the most common examples of feedborne toxins, but also low levels of other chemical toxic substances like pesticides, PCB’s and dioxins might affect gut health. The presence of mycotoxins in poultry feed has been identified as a widespread cause of economic losses due to impaired health status and reduced performance. Adverse effects on the GI tract are probably the major cause of economic losses resulting from trichothecene mycotoxicoses. Among others, cell proliferation and viability, tight junction quality, endocrine secretions and GALT are negatively affected by the presence of toxic chemical components. A reduced secretion of enzymes and histomorphological changes, in combination with reduced absorptive capacity of the enteric cell will have a direct impact on performance and feed conversion. Finally disturbance of the microflora ecosystem and increased level inflammatory cytokines have been well described as a potential consequence of the presence of certain in feed toxins.