ABSTRACT
The gastrointestinal (GI) tract of a healthy adult bird harbours microbial communities that play important roles in maintaining the health and well-being of the host. The mature gut flora competes effectively with any invading organisms that may be harmful to avian or human health and can prevent them from colonizing the digestive tract. Microbial colonization of the GI tract begins soon after hatching (Mead, 2000; Revolledo et al., 2006), but it has been shown that introduction of bacteria into the GI tract can happen already in the pre-hatch state (Klasing, 1998). With coprophagous birds like the domestic fowl or turkey, the transfer of microorganisms is particularly efficient when newly hatched chicks are reared with the adults. This is not possible in industrialized production where chickens are hatched and reared under hygienic conditions. In consequence, the development of the protective microflora is considerably delayed, which leaves the newly hatched chicken exposed to a variety of enteric disease agents (Pivnick and Nurmi, 1982).
