Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level



Poultry Science


Dan J. Donoghue

Committee Member

Ann M. Donoghue

Second Committee Member

Michael F. Slavik

Third Committee Member

Charles Rosenkrans, Jr.


Biological sciences, Campylobacter jejuni, Chicken, Gras, Intra-cloacal, Prebiotic


Campylobacter is the leading cause of foodborne illness worldwide and human illnesses are often associated with consumption of poultry or poultry products. Many strategies have been tried to eliminate Campylobacter from poultry with limited success. One of the strategies to reduce Campylobacter colonization in poultry is by use of probiotics. We conducted 2 separate studies to evaluate the efficacy of probiotics against Campylobacter in broiler chickens. For our first study, GRAS (Generally Regarded as Safe) bacteria were isolated from healthy chickens and tested their efficacy against Campylobacter in vitro. Twenty six isolates with in vitro anti-Campylobacter activity were selected and tested in broiler chickens. Only 3 out of 26 isolates tested, demonstrated a 1-2 log reduction in Campylobacter colonization. To further improve the in vivo efficacy of these 3 isolates, these isolates were given along with 3 different doses of a prebiotic (fructoligosaccharide/FOS or mannanoligosaccharide/MOS). Of all the treatments tested, only one isolate when combined with 0.04% MOS showed a 3 log reduction in Campylobacter. However, the isolates which reduced Campylobacter in vivo in our initial trials failed to reduce Campylobacter in subsequent trials. One possible explanation for such inconsistencies could be due to destruction of probiotic isolates in the acidic environment of stomach. Encapsulation of isolates may overcome this problem, but there is no assurance that these isolates will have efficiency in the lower intestine. In the second study, a procedure to screen the in vivo efficacy of candidate isolates was developed by directly inoculating isolates in the lower intestinal tract via the cloaca. For this study GRAS bacterial isolates with enhanced motility and in vitro anti-Campylobacter activity were selected and tested in vivo by dosing the isolates either orally or intra-cloacally. When isolates were dosed orally, only one isolate showed a 1 log reduction in Campylobacter, but when these isolates were administered intra-cloacally, five of these isolates produced a 1-3 log reduction in cecal Campylobacter counts. These results support the strategy of evaluating the efficacy of potential probiotic isolates via cloacal inoculation prior to undergoing the effort of protecting isolates (e.g., encapsulation) for oral administration.