Three studies were conducted using Clostridium perfringens as an intestinal challenge to produce necrotic enteritis (NE). The studies consisted of two battery screening studies and one production study in floor pens. The purpose of the trials was to determine if reducing the level of microorganisms in feed consumed by broilers reduced the impact of a nonfeed-based Clostridial challenge. In all studies, C. perfringens challenged broilers consuming feed containing lower levels of microorganisms compared to control feed exhibited significantly (P < 0.05) better feed conversion (feed conversion was improved by 14% in battery trials and by 4.2% in the pen trial) than did C. perfringens-challenged broilers consuming control feed. In battery trials, body weight gain and NE-associated mortality were also significantly improved in C. perfringens-challenged broilers consuming feed containing lower levels of microorganisms (16.5% improvement in body weight gain and 72.5% reduction in NE-associated mortality). In the pen trial, body weight gain and NE-associated mortality appeared unaffected by feed microbial quality. No effect was observed on lesion scores. The present data indicate that reducing the level of microorganisms in feed can ameliorate some of the performance losses associated with a Clostridia challenge.