Exploring the gastrointestinal microflora with new molecular techniques
The diverse microbial flora of the gastro intestinal tract contributes to the nutrition, immunology, protection and therefore also health of the host animal. The vast limitations opposed to the investigation of these very important living populations in the gut can be overcome by the use of molecular techniques, which are based on the sequence comparison of nucleic acids (DNA or RNA).
These techniques include the denaturing gel electrophoresis (DGGE), a method to display the genetic diversity of a complex microbial population. In contrast to traditional methods, the DGGE approach allows for profiling gut samples from a large number of individual animals. Thus, it is a suitable tool for detecting shifts in the bacterial population as well as nutritional influences on the composition of bacterial communities in the gut.
Farm animals live in symbiosis with an extensive number of microorganisms inhabiting their gut. Thus, a healthy intestinal microflora is a prerequisite for high performance in terms of live weight gain, feed conversion, milk yield or egg production. Beneficial bacteria contribute to overall gut health by counteracting pathogens through competitive exclusion, production of acidic or bactericidal agents, modulation of the immune system or vitamin synthesis (Ewing and Cole, 1994). Thus, modern animal nutrition focuses on the manipulation of the gut microflora through nutritional means. Researchers are investigating the gut microflora in order to understand the interactions of microorganisms with the host and consequently to enable development of strategies to protect animals from enteric diseases.
The development and colonization of the gastrointestinal tract in young animals is a critical time. In pigs, for example, in the period from birth to weaning, the gut is colonized rapidly by populations such as E. coli, clostridia, streptococci, lactobacilli, bacterioides and bifidobacteria (Stewart, 1997). Weaning is a very stressful process in which piglets are separated from the mother sow and are gradually introduced to solid feed. Hence, piglets in the first few weeks of life are highly susceptible to develop intestinal diseases, which may lead to diarrhea and increased mortality. Therefore, a great concern and interest lies in the protection of piglets by providing them with high quality feed, including health promoting additives such as probiotics and prebiotics. Probiotic and prebiotic feed additives are potential alternatives for antibiotic growth promoters (AGP), which are already prohibited in the European Union and will most likely be banned in animal production world wide in the future. There exist several definitions of a probiotic, but generally it is stated as a living microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance. Prebiotics are defined as non-digestible feed ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improve host health (Gibson, 1995). The beneficial impact of probiotic supplementation on weight gain has been shown in a 56-day trial with pigs.
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Article made possible through the contribution of BIOMIN GmbH