Optimized Necrotic Enteritis Model Producing Clinical and Subclinical Infection of 'Clostridium perfringens' in Broiler Chickens

Abstract

In this study we assessed the roles of 'Eimeria' infection and dietary manipulation (feeding a diet with a high level of fishmeal) in an Australian necrotic enteritis (NE) challenge model in broiler chickens. An experiment was designed to test the hypothesis that 'Eimeria' infection and dietary manipulation, i.e., inclusion of fishmeal in the diet, are necessary to induce NE experimentally. The results showed that the combination of 'Eimeria' administration and fishmeal feeding had a significant effect on induction of clinical and subclinical 'Clostridium perfringens' infection. The majority of the mortality that occurred during the second week of the trial was due to an NE outbreak following the 'C. perfringens' challenge. The mortality rate of the birds was 12.00% for the high-fishmeal (HFM; 500 g/kg) group and 9.33% for the low-fishmeal (LFM; 250 g/kg) group when the birds were subjected to 'C. perfringens' and 'Eimeria'. Fishmeal alone did not induce significant mortality in birds challenged only with 'C. perfringens' but showed a significantly higher 'C. perfringens' count than the non-fishmeal (NFM) control group. 'Eimeria' administration had a significant effect on NE-related mortality but did not have an effect on the 'C. perfringens' count. In accordance with the time course of bird mortality, it can be determined that of the 3 successive days of oral gavage with 'C. perfringens', the first inoculation was essential for inducing NE, but the third had no additional effect on NE-related mortality. Also, reducing the fishmeal level from 500 to 250 g/kg had no negative impact on the reproducibility of the model. It may be concluded that NE can be consistently induced under experimental conditions by feeding broilers a diet containing 250 g/kg fishmeal, using a single inoculation with low numbers of 'Eimeria', administering one or two oral 'C. perfringens' inoculations, and maintaining appropriate ambient temperatures and diets.