Date of Completion


Embargo Period



probiotics, in ovo, Salmonella, broiler, layer, growth-promoter

Major Advisor

Dr. Mary Anne Amalaradjou

Associate Advisor

Dr. Kumar Venkitanarayanan

Associate Advisor

Dr. Michael Darre

Field of Study

Animal Science


Doctor of Philosophy

Open Access

Open Access


The United States is the leading producer of broiler meat in the world and second to China in table egg production. In the last year, the US poultry industry produced 55.6 billion pounds of broiler meat and 8.8 billion table eggs. Besides genetics, the health status of the chicken accounts for ~67% of the production performance in birds. Poultry products have been linked with various foodborne outbreaks, including salmonellosis. Since the FDA has banned the use of antibiotics for non-treatment purposes in poultry, alternatives have been sought to replace antibiotics as growth promoters. In this regard, lactic acid bacteria (LAB) have been demonstrated to impart several health benefits and could potentially be used as antibiotic alternatives to enhance production and improve health in poultry. However, most studies investigating the growth promoting attributes of probiotic cultures were limited to their dietary supplementation following hatch. In the case of broilers and layers, it has been determined that embryonic and perinatal growth and development play a critical role in subsequent growth and performance. Hence the present study characterized the probiotic potential of Lactobacillus delbreuckii ssp. bulgaricus NRRL-B-548 (LD), L. paracasei DUP-13076 (LP), and L. rhamnosus NRRL- B-442 (LR) and investigated their ability to promote growth in chicken when applied as an in-ovo and in-feed supplement.

The genotypic and phenotypic characterization revealed that the aforementioned LAB isolates were able to survive under simulated physiological conditions in vitro. Additionally, the LAB isolates inhibited Salmonella enterica colonization in vitro by modulating various virulence factors. Most importantly, early in ovo and in-feed supplementation of LABs demonstrated that these probiotic strains can be used as an effective alternative to AGPs since they were able to stimulate the growth and development of chicken and improved the feed conversion ratio. Therefore, LD, LP and LR could potentially be used to promote growth in chicken and improve the microbiological safety of poultry products. However, large-scale chicken studies are warranted for further validation


Available for download on Tuesday, August 19, 2025