Date of Award


Document Type


Degree Name

Bachelor of Science



First Advisor

Lester Caudill


Antibiotics are used in poultry production as prophylaxis, curative treatment, and growth promotion. The first use is as prophylaxis, or prevention of common bacterial diseases. The crowded conditions in concentrated animal feeding operations necessitate management of infectious disease to ensure overall animal health and the profitability of such operations. In these farms, between 20,000 and 125,000 birds are raised in shed-like enclosures [3], with an average of less than one square foot of space per chicken [34]. Antibiotics are currently used in chicken farms to manage and prevent common bacterial diseases such as respiratory and digestive tract infections, as well as more serious and life threatening infections such as necrotic enteritis, coccidiosis, and infections caused by some strains of Salmonella and Escherichia coli [15]. Prophylactic antibiotics are usually added to the water supply [22], [15] and taken by all chickens in the farm. Since the purpose of these antibiotics is prevention rather than treatment, they are administered at lower levels than antibiotics used for treatment and are deemed sub-therapeutic, meaning they are below the dose required to kill or stop the growth of most bacteria [40]. Using antibiotics in this way helps keep the large and concentrated populations of chickens healthy for their 48-day life before slaughter, but it also contributes to the problem of antibiotic resistance, as sub-therapeutic doses of antibiotics select for increased resistance [40]. Unlike the use of antibiotics for growth promotion, using antibiotics as prophylaxis is legal and widely practiced.