Theses and Dissertations

Issuing Body

Mississippi State University


Pulido-Landinez, Martha

Committee Member

Banda, Alejandro

Committee Member

Magee, Danny L.

Committee Member

Armour, K. Natalie

Date of Degree


Original embargo terms

MSU Only Indefinitely

Document Type

Graduate Thesis - Campus Access Only


Veterinary Medical Science

Degree Name

Master of Science


College of Veterinary Medicine


Veterinary Medical Science Program


This study was conducted to compare the gizzard integrity between two broilers flocks, one under a no antibiotics ever (NAE) program and the other from a conventionally raised flock (CONV). One-hundred Ross 708 x Ross YPM broiler chickens from two flocks of the same company but raised under two distinct management systems were allocated for this study. At 1, 14, 28 and 42 days of age, birds from both flocks were received at the Poultry Research and Diagnostic Laboratory. Gross and histopathologic evaluations of gizzard lesions and microbiological determinations of the gizzard mucosa were conducted and body and gizzard weights were recorded. Birds under both programs showed very similar growth rates, however gizzards were heavier in the birds under the CONV program. The birds under the NAE program had higher gross gizzard lesion scores at days 1, 14, 28 and 42, with statistical significance at day 42 (P<0.05). Histopathologically, the birds under the NAE program had greater gizzard lesion scores compared to the CONV flock at days 14 and 28, however no statistical significance was established. Escherichia coli was more frequently isolated from the birds under the CONV program. According to these observations, gross and microscopic gizzard lesions appeared to be more associated with the NAE program.