Theses and Dissertations

Issuing Body

Mississippi State University


Thaxton, Vizzier Yvonne

Date of Degree


Document Type

Dissertation - Open Access



Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Food Science, Nutrition and Health Promotion


The objectives of this study were first, to investigate the effect of stress and ascorbic acid (AA) supplement during stress on intestinal microflora of broilers and layers, and secondly, to determine nitric oxide (NO) production in intestinal tract of broilers during stress, when supplemented with L-arginine, and NO production in cecal bacteria. The intestinal microflora from broilers and layers were analyzed for bacterial populations during stress and when supplemented with ascorbic acid. In both studies, stress response was induced by adrenocorticotropic hormone (ACTH) via a mini osmotic pump for 7 days, and intestinal samples were collected before and after stress response was induced. During stress, there were no significant effects on intestinal bacterial populations, but changes in intestinal microflora were found in stressed layers and broilers. When AA was supplemented during stress, both short-term and long-term, the microbial population was changed. Cecal NO production during stress, cecal bacterial NO production, and large intestinal NO production when L-arginine was supplemented in broilers were determined as nitrite using Griess reagents. The stress response was induced as in the previous studies. The cecal pouches were collected at day 7 after ACTH insertion. Nitric oxide production by the ceca of broilers during stress was decreased. The cecal bacterial NO production was determined in vitro. The cecal bacteria that produced NO were identified as Lactobacillus fermentum, and Clostridium butyricum. Supplementing with L-arginine, Nù -nitro-L- arginine methyl ester (L-NAME), and sodium nitrate did not affect bacterial NO production on MRS agar incubated anaerobically, but sodium nitrate did affect bacterial NO production on tryptic soy and anaerobic agar incubated aerobically and anaerobically, respectively. L-arginine was supplemented in broiler diet to determine the effect on intestinal NO production and microbial populations. Supplemented with L-arginine affected cecal NO production, but did not affect large intestinal NO production or microbial populations. The positive correlation coefficient between NO contents and bacterial populations was only observed in the large intestine when L-arginine was supplemented in the diet.