Theses and Dissertations

Issuing Body

Mississippi State University


Zhai, Wei

Committee Member

Peebles, E. David

Committee Member

Macklin, Kenneth S.

Date of Degree


Document Type

Graduate Thesis - Open Access


Poultry Science

Degree Name

Master of Science


College of Agriculture and Life Sciences


Department of Poultry Science


The effects of dietary antimicrobial removal and Bacillus subtilis supplementation on the growth and intestinal health of male broilers were investigated. Birds were fed either a control, antimicrobial, or a B. subtilis probiotic diet at different feeding phases. Birds were challenged with a 10 × dose of a coccidiosis vaccine. Supplementation of B. subtilis in for antimicrobials in the late grower and early finisher phases improved growth similar to birds fed antimicrobials until withdrawal, while antimicrobial removal without B. subtilis supplementation in those periods hindered growth. The improved growth suggests that the probiotic was able to alleviate the stress of the challenge compared to antimicrobial removal. Processing yields were improved with antimicrobial removal and B. subtilis supplementation in late grower and early finisher phase. Intestinal health was improved with lower intestinal lesions when antimicrobial were removed and B. subtilis supplemented suggesting the reduction of Eimeria species from colonizing the intestine.



Coccidiosis||Bacillus subtilis||Probiotic||Antibiotic||Broiler