A series of experiments were conducted to examine the effect of chemical composition of the diet on intestinal Clostridium perfringens populations and necrotic enteritis (NE) in broiler chickens. In the first experiment, birds were fed high concentrations of dietary protein (fish meal or soy protein concentrate) and soluble fiber (guar gum). Clinical NE was not observed, however, there was a high level of C. perfringen colonization especially in guar gum fed birds. The next set of experiments examined the effect of various levels of DL-Met or MHA-FA on C. perfringen and other intestinal microbes. These experiments demonstrated a significant reduction (P < 0.05) in C. perfringen growth with methionine supplementation in ileum and cecum. The results suggest that both DL-Met and MHA-FA may reduce intestinal populations of C. perfringen in broiler chickens when used in high concentrations. The next three experiments were conducted to examine the effect of dietary glycine levels on gut C. perfringen populations, α-toxin production and NE lesion scores. Majority of birds showed clinical signs of disease with 4.16-8.33% mortality. There was a direct correlation between intestinal C. perfringen populations, NE lesions scores and mortality with dietary glycine level. However, due to the use of gelatin as the dietary source of glycine in these experiments, the diets also contained high proline levels which confounded our results. The last study was conducted to establish a direct causative relationship between dietary glycine concentration and C. perfringen growth and/or NE in broiler chickens using encapsulated amino acids. Birds fed diets containing high levels of encapsulated glycine had higher NE lesion scores than those fed encapsulated proline or no encapsulated amino acids, thus demonstrating a direct effect of glycine on intestinal C. perfringen growth. It is concluded that amino acid composition of dietary protein is an important determinant of intestinal microbial growth, particularly C. perfringen, and could affect incidence of NE in broiler chickens
