- A lot of misunderstandings in chicken gut microbiota stems from the fact that we consider chicks from hatcheries as a control, reference, group
- There is no age dependent development of gut microbiota in chickens
- If chicks are provided with source of adult type of microbiota, gut colonisation is accomplished within the first week of life
- At the same moment, chicks become resistant to infection with Salmonella, pathogenic E. coli or Clostridium perfringens
The following information is valid for gut microbiota of chickens but some of this information can be extrapolated to other warm-blooded species including humans. Intestinal tract is colonised by hundreds of bacterial species. Different species colonise small intestine (mostly Lactobacilli) and other species are present in the caecum or colon (all other strict anaerobes associated with gut microbiota, e.g. Bacteroides, Prevotella, Megamonas, Megasphaera, Faecalibacterium). Despite this, only a few species from genera Lactobacillus, Bifidobacterium, Enterococcus or Bacillus are used as probiotics. None of these bacteria colonise intestinal tract permanently and must be continuously supplied. Genu Bacillus even does not belong among core gut microbiota. Our results even points towards negative effect of Lactobacilli when these are provided to newly hatched chicks. This observation should not be generalised to other host species and likely, this is specific for high doses of Lactobacilli and newly hatched chicks with underdeveloped microbiota from hatcheries.
There are additional specifics of Gallus gallus. Chicks are hatched in hatcheries without any contact with adult hens and natural microbiota transfer from parents to offspring is interrupted. The chickens are therefore colonised by random microbiota from environment which may or may not be of ideal composition. From here, dogma on gradual development of gut microbiota originates. However, this is biologically mistaken. If you are not convinced yet, set up an experiment in which you will place newly hatched chicks in a contact with an adult hen and colonisation of chick intestinal tract by adult type of microbiota will be a matter of 2 o 3 days. This is why competitive exclusion product have been used successfully in chickens for more than 40 years. Positive experience with competitive exclusion also indicates that there are bacteria different from Lactobacilli or Bifidobacteria which affect chicken gut health positively and which can be used as new types of probiotics, as an elegant alternative to use of antibiotics.