Probiotics and prebiotics in animal nutrition

There has been a close relationship between microbes residing in the gastrointestinal tract (GIT) and the animal host during the long course of evolution (Ley et al. 2008). Nowadays the microbiota within the GIT of mammals can be considered a metabolically active organ: culture independent studies of the human microbiota recently identified a complex symbiotic environment with a wide biodiversity with more than 1,000 bacterial phylotypes representing more than 7,000 strains and with a high number of cells that can reach 1014 (Backhed et al. 2005, Murphy et al. 2009). Under normal circumstances, commensal bacteria are an essential health asset with a nutritional function and a protective influence on the intestinal structure and homeostasis. The intestinal microbiota promotes supply, digestion and absorption of nutrients, improves growth performance, prevents pathogen colonization, and shapes and maintains normal mucosal immunity. Although the intestinal microbiota is complex and the role of most of the bacteria in providing benefit to the host is not clear, bacterial species of the genera Lactobacillus and Bifidobacterium have been shown to supply beneficial host effects because of their metabolic function and end products. Regulating the homeostasis, which is maintained by the microbiota, by enhancing its beneficial components, it could be possible to treat various intestinal disorders and maintain host well-being (O’Hara and Shanahan 2007).