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A necrotic enteritis (NE) challenge model in broiler chickens has been developed and modified at the University of New England. However, detail on the roles of predisposing factors and the causative agent ('Clostridium perfringens') on the performance and mortality of birds have not been thoroughly investigated. In this study, we examined the effects of fishmeal feeding, Eimeria inoculation and 'C. perfringens' challenge on the growth performance and NE-associated mortality of the birds using a 2 x 2 x 2 experimental design. Fishmeal addition significantly elevated body weight gain during the second week, but this effect was not evident thereafter. Eimeria inoculation significantly reduced body weight gain in weeks 2, 3 and 4, but not in week 5. In contrast, 'C. perfringens' challenge only reduced body weight gain of the birds in week 4. Additionally, interactions among the factors on body weight gain of the birds were detected in weeks 3 and 4. The combination of Eimeria inoculation and 'C. perfringens' challenge significantly increased the NE-related mortality of the birds whereas 25% fishmeal addition in the starter diet did not show such an effect. We speculate that this may be due to the high crude protein level in the basal starter diet which reduced the effect of fishmeal in the corresponding treatment groups. It is suggested that the minimal level of crude protein required to induce necrotic enteritis would be an interesting topic for further investigation. |
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