The microorganisms most commonly observed are bacteria and yeast. There are two populations of microorganisms that are found within the gastrointestinal (GI) tract of poultry. Initially, the autochthonous bacteria colonize the gut by inoculation caused by environmental exposure and normal feeding activities of this bird.
The Second, allochthonous bacteria, are exogenous in character and therefore are introduced as a dietary supplement into the GI tract via the feed or drinking water since direct fed microbial (DFM) or probiotics .
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Modern nutritionists use the conditions of probiotics and DFM interchangeably, however, now the term probiotic is most often used. For the review, the expression, probiotic, will be employed to denote the usage of probiotics or direct-fed microbials.
Some information in the literature implies that allochthonous bacteria introduced via probiotics may stop the infection and colonization of the GI tract by opportunistic pathogens.
The introduction of probiotics is believed to prevent or attenuate the growth of clinical enteric pathogens in poultry, leading to enhanced growth and performance of the host bird.
Probiotics have been live microbial feed autochthonous and allochthonous (probiotic) bacteria Supplements that beneficially affect the host animal by enhancing its intestinal microbial balance or a live microbial feed that is essential to health.
They may include only one, or many distinct bacterial species. The mechanisms of action of various bacterial strains in a probiotic consortium may differ. Additionally, different genotypes within the same species may have different biological effects that could be synergistic or antagonistic.
In poultry production systems, efficacy and benefits could be specifically defined. Any feed supplement or treatment that enriches poultry health and performance as measured by improved animal health, feed or growth efficiency.