Gut health: The new paradigm in animal production?

Modern livestock and poultry operations have undergone dramatic changes in production practices over the last 50 years. Genetic selection for high growth rates and reproductive traits as well as improved management techniques and dietary requirements have led to increased performance standards in all livestock operations. However, it is reasonable to question whether, in the near future, animal performance will reach a ceiling due to genetic and/or physiological limits. It is with these limits in mind that over the last 5+ years, the expression “gut health” has entered the collective consciousness of animal industries and research. The expression “gut health” has become the standard in the scientific literature and animal production industries to describe animal health. However, there is no clear definition for the term gut health. Furthermore, from a scientific point of view, no one can state what gut health is, how it can be defined, and, most importantly, how it can be measured. Since we all know that the gut = the gastrointestinal tract, the definition of gut health hinges on defining “health”. The simple definition would be “absence of overt disease”. However, overt disease is not required to affect animal production. Perhaps a more meaningful definition would be defined as the ability of the gut to perform normal physiological functions and to maintain homeostasis, thereby supporting its ability to withstand infections and non-infectious stressors. This definition incorporates the underlying components of gut health: effective digestion and absorption of food, a stable gut microbial population, structure and function of the gut barrier, and effective function of the immune system, all of which play a critical role in gut physiology, the productivity of the animal, and its well-being. Comprehension of gut health requires the elucidation of the interactions between all of these components. Understanding the interactions between of these diverse fields underscores the scope of areas encompassed by gut health. Newly acquired knowledge has positioned research in “gut health” to advance rapidly in both basic and applied directions. Forces that will remodel the field in the next decade will be derived from public concerns about food safety and the explosive and novel use of new research tools stemming from systems biology (‘omics). Lastly, the developments of measurements (biomarkers) of gut heath are required for research and producers managers. As examples, we suggest:
• systemic markers that have well-defined linkages to gut health,
• validation of factors involved in normal barrier functions and intestinal permeability, markers associated with epithelial injury and repair that can be traced back to gut dysfunction,
• identification of markers that specify the gut’s ability to absorb, transport, and secrete major nutrients,
• identification of hormonal markers of neuroendocrine function in the digestive system relevant to gut function or dysfunction,
• markers validating the functional presence of beneficial bacteria or bacterial products (pre-or probiotics),