No description available.

x, 123 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Entomology, Waite Agricultural Research Institute, 1973

Ph.D. thesis 1970 from the Dept. of Plant Pathology, Waite Institute, University of Adelaide / iii, 97 leaves : ill., graphs / Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Entomology, Waite Agricultural Research Institute, 1973.

No description available.

Previous reports have shown that some bacteria utilize a dissimilatory nitrate reductase enzyme (NR) in anaerobic environments. This enzyme reduces nitrate to nitrite and also has been shown to co-metabolize chlorate to cytotoxic chlorite. A commercially available competitive exclusion (CE) product was evaluated for its nitrate reductase activity and therefore its experimental chlorate product (ECP) sensitivity. Of the 29 constituent bacteria of the CE culture, 11 had slight utilization of NR, 3 had moderate utilization of NR; the remaining were NR negative (with slight and moderate utilization: >0.1 to < 1.0 mM and > 1.0 mM nitrate utilized within 6 h, respectively). In vivo studies utilizing CE and ECP showed significant reductions in Salmonella. Although some of the bacteria were affected by ECP, the combined effect of the CE culture and ECP were effective in reducing Salmonella. Clostridium perfringens (CP) is a pathogen in the commercial poultry industry, which is the etiologic agent of necrotic enteritis (NE). Day-of-hatch broilers were fed a wheat diet and assigned to the following groups: control, commercial coccidia vaccine, commercial bursal disease vaccine, or the combination of the two, and challenged with CP in order to develop a disease model. Broilers in each treatment group had significant increases (P≤ 0.05) in lesion scores, mortality, and CP incidence. As pressure mounts for discontinuing the use of antibiotics in the agriculture industry, it is important to develop new strategies to combat these costly enteric pathogens. In vitro investigations evaluated a mixed gut culture with CP and the ECP at 5 mM or a 10 mM concentrations, over time. By 3 h there was a reduction (P≤ 0.05) in the 5 mM ECP and 10 mM ECP treatment groups. In vivo studies showed significant reductions in the incidence of CP and populations of intrinsic E. coli in all of the chickens provided ECP in the drinking water. Birds administered ECP in the feed showed significant reductions in lesion scores, incidence of CP and also had reduced E. coli log10 values. These results show that an ECP could provide the industry with a new management tool for controlling NE.

A series of experiments were conducted to examine the effect of chemical composition of the diet on intestinal <i>Clostridium perfringens</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> and other intestinal microbes. These experiments demonstrated a significant reduction (P < 0.05) in <i>C. perfringen</i> growth with methionine supplementation in ileum and cecum. The results suggest that both DL-Met and MHA-FA may reduce intestinal populations of <i>C. perfringen</i> in broiler chickens when used in high concentrations. The next three experiments were conducted to examine the effect of dietary glycine levels on gut <i>C. perfringen</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> growth. It is concluded that amino acid composition of dietary protein is an important determinant of intestinal microbial growth, particularly <i>C. perfringen</i>, and could affect incidence of NE in broiler chickens.

A series of experiments were conducted to examine the effect of chemical composition of the diet on intestinal <i>Clostridium perfringens</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> and other intestinal microbes. These experiments demonstrated a significant reduction (P < 0.05) in <i>C. perfringen</i> growth with methionine supplementation in ileum and cecum. The results suggest that both DL-Met and MHA-FA may reduce intestinal populations of <i>C. perfringen</i> in broiler chickens when used in high concentrations. The next three experiments were conducted to examine the effect of dietary glycine levels on gut <i>C. perfringen</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> 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 <i>C. perfringen</i> growth. It is concluded that amino acid composition of dietary protein is an important determinant of intestinal microbial growth, particularly <i>C. perfringen</i>, and could affect incidence of NE in broiler chickens.

Previous reports have shown that some bacteria utilize a dissimilatory nitrate reductase enzyme (NR) in anaerobic environments. This enzyme reduces nitrate to nitrite and also has been shown to co-metabolize chlorate to cytotoxic chlorite. A commercially available competitive exclusion (CE) product was evaluated for its nitrate reductase activity and therefore its experimental chlorate product (ECP) sensitivity. Of the 29 constituent bacteria of the CE culture, 11 had slight utilization of NR, 3 had moderate utilization of NR; the remaining were NR negative (with slight and moderate utilization: >0.1 to < 1.0 mM and > 1.0 mM nitrate utilized within 6 h, respectively). In vivo studies utilizing CE and ECP showed significant reductions in Salmonella. Although some of the bacteria were affected by ECP, the combined effect of the CE culture and ECP were effective in reducing Salmonella. Clostridium perfringens (CP) is a pathogen in the commercial poultry industry, which is the etiologic agent of necrotic enteritis (NE). Day-of-hatch broilers were fed a wheat diet and assigned to the following groups: control, commercial coccidia vaccine, commercial bursal disease vaccine, or the combination of the two, and challenged with CP in order to develop a disease model. Broilers in each treatment group had significant increases (P≤ 0.05) in lesion scores, mortality, and CP incidence. As pressure mounts for discontinuing the use of antibiotics in the agriculture industry, it is important to develop new strategies to combat these costly enteric pathogens. In vitro investigations evaluated a mixed gut culture with CP and the ECP at 5 mM or a 10 mM concentrations, over time. By 3 h there was a reduction (P≤ 0.05) in the 5 mM ECP and 10 mM ECP treatment groups. In vivo studies showed significant reductions in the incidence of CP and populations of intrinsic E. coli in all of the chickens provided ECP in the drinking water. Birds administered ECP in the feed showed significant reductions in lesion scores, incidence of CP and also had reduced E. coli log10 values. These results show that an ECP could provide the industry with a new management tool for controlling NE.

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Pathology. Title from title-page of electronic thesis. Bibliography: leaves 105-117.