Two necrotic enteritis predisposing factors, dietary fishmeal and 'Eimeria' infection, induce large changes in the caecal microbiota of broiler chickens

Abstract

It is widely established that a high-protein fishmeal supplemented starter diet and 'Eimeria' infection can predispose birds to the development of clinical necrotic enteritis symptoms following 'Clostridium perfringens' infection. However, it has not been clearly established what changes these treatments cause to predispose birds to succumb to necrotic enteritis. We analysed caecal microbiota of 4 groups of broilers (n = 12) using deep pyrosequencing of 16S rDNA amplicons: (1) control chicks fed a control diet, (2) 'Eimeria' infected chicks fed control diet, (3) chicks fed fishmeal supplemented diet and lastly (4) both fishmeal fed and 'Eimeria' infected chicks. We found that the high-protein fishmeal diet had a strong effect on the intestinal microbiota similar to the previously reported effect of 'C. perfringens' infection. We noted major changes in the prevalence of various lactobacilli while the total culturable 'Lactobacillus' counts remained stable. The Ruminococcaceae, Lachnospiraceae, unknown Clostridiales and Lactobacillaceae families were most affected by fishmeal with increases in a number of operational taxonomic units (OTUs) that had previously been linked to Crohn's disease and reductions in OTUs known to be butyrate producers. 'Eimeria' induced very different changes in microbiota; Ruminococcaceae groups were reduced in number and three unknown 'Clostridium' species were increased in abundance. Additionally, 'Eimeria' did not significantly influence changes in pH, formic, propionic or isobutyric acid while fishmeal induced dramatic changes in all these measures. Both fishmeal feeding and 'Eimeria' infection induced significant changes in the gut microbiota; these changes may play an important role in predisposing birds to necrotic enteritis.