Emerging technologies in microbial ecology aid in understanding the effect of monensin in the diets of broilers in regard to the complex disease necrotic enteritis

Necrotic enteritis is a complex disease condition of broiler chickens, commercial layer pullets, and turkeys and requires the presence of a toxigenic strain of Clostridium perfringens, alteration of bird diets, and damage to the intestinal epithelium. All of these alone, but especially in combination, result in significant alterations of the intestinal microflora. The intestinal microflora is part of a complex ecosystem that is involved in augmenting intestinal development, immune surveillance, and competitive exclusion against pathogenic organisms. However, when the microflora fails to protect the mucosa from pathogens, antimicrobials are used to reduce the numbers of pathogenic organisms or to prevent their colonization of the intestine. We were interested in studying the effects of monensin on the bacterial community within the ileum of chickens because ionophore antimicrobials are commonly used to prevent Eimeria infections in broilers. We used two 16S ribosomal DNA community analysis protocols, terminal restriction fragment length polymorphism analysis combined with 16S rDNA clone libraries. These methods showed that monensin caused significant alterations in the microbial community structure of the ileum. Whereas the ileal bacterial community of control birds primarily consisted of lactobacilli, monensin-treated birds had communities rich in clostridia. None of the birds exhibited signs of intestinal disease or mucosal lesions, which suggested that the clostridia were avirulent. Although the therapeutic benefits of monensin may largely result from its anticoccidial effects, its ability to foster a competitively exclusive bacterial community may contribute to the intestinal health of birds, thus preventing the development of necrotic enteritis.