Todd Riley Callaway Associate Professor Animal & Dairy Science
Portrait of Todd Riley Callaway
Mailing Address Athens, CAES Campus Stru Animal Dairy Sci -, 425 River Road, Athens, GA 30602
Shipping Address Athens, CAES Campus Stru Animal Dairy Sci -, 425 River Road, Athens, GA 30602

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Portrait of Todd Riley Callaway


Dr. Todd Callaway has joined the faculty of the Department of Animal and Dairy Science at UGA.  Todd is a ruminant microbiologist who grew up on a small horse, dairy, and beef farm and received his B.S. and M.S. degrees from the University of Georgia in Animal and Dairy Science in 1993 and 1996, respectively.  He then went on to receive his Ph.D. degree in Microbiology from Cornell University in 1999.  Dr. Callaway’s research in graduate school focused on how the bacteria in the rumen of cattle could adapt and become resistant to ionophores, and how ionophore usage could be enhanced or replaced using non-antibiotic approaches.  

Following graduate school, Dr. Callaway joined the Agricultural Research Service of the USDA (USDA-ARS) in 2000 and served as a research microbiologist in the Food and Feed Safety Research Unit at the Southern Plains Agricultural Research Center, in College Station, Texas.  There his research mission was to reduce food-borne pathogens such as Salmonella and E. coli O157:H7 in animals prior to slaughter.  As part of his research focus, Dr. Callaway focused on the intestinal microbiome and the impacts of diet on the microbial population and host susceptibility to pathogen colonization.  His research has been supported by the: National Cattlemen’s Beef Association, National Dairy Board, National Pork Board, U.S. Poultry and Egg Foundation, and numerous companies from around the world.  In 2016, Dr. Callaway served as the Acting and subsequently became the National Program Leader for Food Safety for USDA-ARS, with a portfolio of research that included: On-Farm Food Safety, Antimicrobial Resistance, and Microbiome research.

During his research career, Dr. Callaway has published more than 200 refereed journal articles, more than 25 book chapters, and 2 books entitled “Direct Fed Microbials” and “On-Farm Strategies to Control Foodborne Pathogens”.  Dr. Callaway received the American Society of Animal Science Early Career Research Award and the USDA/ARS Early Career Scientist of the Year Awards in 2007.  Dr. Callaway has chaired numerous scientific meetings and research panels.  Todd is excited to begin again working with the producers of Georgia to understand their specific needs and how manipulation of the ruminal microbes can improve profitability on the farm.  His research at UGA is going to focus on the role of the ruminal microbes in the nutrition of cattle, and how the complex environment of the cattle gastrointestinal tract can impact food safety.

B.S., University of Georgia
M.S., University of Georgia
Ph.D., Cornell University

Description of Research Interests

The microbial population (microbiome) of the gastrointestinal tract of animals is a diverse and dense, and represents a resource that can be used to improve animal performance and efficiency, animal health, animal welfare and food safety. By understanding how the microbiome is affected by diet and environmental factors, we can improve animal production efficiency and sustainability. Therefore, my research is focused on unravelling the microbial ecology of the gut in food animals, and how this can affect foodborne pathogenic bacterial populations as well as antimicrobial resistance transfer. Further interests included the impacts of microbial physiology on the microbial population, development of intervention strategies to reduce foodborne pathogenic bacteria in food animals, and understanding how the microbiome can affect host health and productivity as well as behaviors.

Courses Taught

ADSC 4360/6360- Ruminant Nutrition
ADSC 8150- Gastrointestinal Microbial Ecology of the Ruminant
ADSC 8885- Current literature in ruminant nutrition and microbiology

Selected Recent Publications

Callaway, T. R., S. Block, K. J. Genovese, R. C. Anderson, R. B. Harvey, and D. J. Nisbet. 2012. Impact of by-product feedstuffs on E. coli O157:H7 and Salmonella Typhimurium in pure and mixed ruminal and fecal culture in vitro. Agric. Food Anal. Bacteriol. 2:139-148.

Hristov, A. N., T. R. Callaway, C. Lee, and S. E. Dowd. 2012. Ruminal bacterial, archaeal, and fungal diversity of dairy cows with normal and reduced ruminal fauna. J. Anim. Sci. 90:4449-4457.

Edrington, T. S., R. L. Farrow, B. H. Carter, G. R. Hagevoort, T. R. Callaway, R. C. Anderson and D. J. Nisbet. 2012. Age and diet effects on fecal populations of a multi-drug resistant Escherichia coli in dairy calves. Agric. Food Anal. Bacteriol. 2:162-174.

Edrington, T. S., S. E. Dowd, R. Farrow, R. Hagevoort, T. R. Callaway, R. C. Anderson, and D. J. Nisbet. 2012. Development of colonic microflora as assessed by pyrosequencing in dairy calves fed waste milk. J. Dairy Sci. 95:4519-4525.

Broadway, P. R., T. R. Callaway, J. A. Carroll, J. R. Donaldson, R. J. Rathmann, B. J. Johnson, J. T. Cribbs, L. M. Durso, D. J. Nisbet, and T. B. Schmidt. 2012. Evaluation of the ruminal bacterial diversity of cattle fed diets containing citrus pulp pellets (CPP) using bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP). Agric. Food Anal. Bacteriol. 2:297-308.

Ramirez Ramirez, H. A., K. Nestor, L. O. Tedeschi, T. R. Callaway, S. E. Dowd, S. C. Fernando, and P. J. Kononoff. 2012. The effect of brown midrib corn silage and dried distillers grains and solubles on milk production nitrogen utilization, and microbial community structure in dairy cows. Can. J. Anim. Sci. 92:365-380.

Rostagno, M. H., and T. R. Callaway. 2012. Pre-harvest risk factors for Salmonella enterica in pork production. Food Res. Intl. 45:634-640.

Callaway, T. R., T. S. Edrington, R. B. Harvey, R. C. Anderson and D. J. Nisbet. 2012. Prebiotics in food animals, a potential to reduce foodborne pathogens and disease. Romanian Biotechnol. Lett. 17:7808-7816.

Duoss, H. A., J. R. Donaldson, T. R. Callaway, J. A. Carroll, P. R. Broadway, J. M. Martin, S. Shields-Menard, and T. B. Schmidt. 2013. Survival of Escherichia coli O157:H7 (ATCC 43888) transformed with either the pAK1-lux or pXEN-13 plasmids in bovine mixed ruminal and fecal microorganism fluid. Foodborne Path. Dis. Foodborne Path. Dis. 10:1-5.

Duoss, H. A., T. B. Schmidt, T. R. Callaway, J. A. Carroll, J. M. Martin, S. A. Shields-Menard, P. R. Broadway, and J. R. Donaldson. 2013. Effect of citrus by-products on growth of O157:H7 and non-O157 Escherichia coli serogroups within in vitro bovine ruminal microbial fermentations. Int. J. Microbiol. 2013: Article ID 398320, doi:10.1155/2013/398320.

Poole, T. L., J. Suchodolski, T. R. Callaway, R. L. Farrow, G. H. Loneragan, and D. J. Nisbet. 2013. The effect of chlortetracycline on fecal microbial populations in growing swine. J. Global Antimicrob. Res. 1:171-174.

Wilson, J. G., T. C. McLaurin, S. Shields-Menard, T. B. Schmidt, J. A. Carroll, T. R. Callaway, and J. R. Donaldson. 2013. Effect of citrus pulp on the viability of Saccharomyces boulardii in the presence of enteric pathogens. Agric. Food Anal. Bacteriol. 3:303-311.

Krause, D. O., T. G. Nagaraja, A. D. G. Wright, and T. R. Callaway. 2013. Board Invited Review: Rumen microbiology: Leading the way in microbial ecology. J. Anim. Sci. 91:331-341.

Callaway, T. R., T. S. Edrington, G. H. Loneragan, M. A. Carr, and D. J. Nisbet. 2013. Shiga Toxin-Producing Escherichia coli (STEC) ecology in cattle and management based options for reducing fecal shedding. Agric. Food Anal. Bacteriol. 3:39-69.

Callaway, T. R., T. S. Edrington, G. H. Loneragan, M. A. Carr, and D. J. Nisbet. 2013. Current and near-market intervention strategies for reducing Shiga Toxin-Producing Escherichia coli (STEC) shedding in cattle. Agric. Food Anal. Bacteriol. 3:103-120.

Norman, K. N, R. B. Harvey, K. Andrews, M. E. Hume, T. R. Callaway, R. C. Anderson, and D. J. Nisbet. 2014. Survey of Clostridium difficile in retail seafood in College Station, Texas. Food Add. Contam.. 31:1127-1129.

Zhang, Y., R. Long, C. Warzecha, E. Latham, M. E. Hume, T. R. Callaway, M. R. O’Neil, R. C. Beier, R. C. Anderson, and D. J. Nisbet. 2014. Characterization of bovine ruminal and equine cecal microbial populations enriched for enhanced nitro-toxin metabolizing activity. Anaerobe (Accepted 17 December).

Callaway, T. R., T. S. Edrington, and D. J. Nisbet. 2014. Isolation of E. coli O157:H7 and Salmonella from migratory brown-headed cowbirds (Molothrus ater), common grackles (Quiscalus quiscula) and cattle egrets (Bubulcus ibis). Foodborne Path. Dis. 11:791-794

Franz, E., P. Delaquis, M. Stefano, L. Beutin, K. Gobius, D. Rasko, J. Bono, N. French, J. Osek, B. A. Lindstedt, M. Muniesa, S. Manning, J. LeJeune, T. Callaway, S. Beatson, M. Eppinger, T. Dallman, K. Forbes, H. Aarts, D. Pearl, and N. J. C. Strachan. 2014. Exploiting the explosion of information associated with whole genome sequencing to tackle Shiga toxin producing Escherichia coli (STEC) in global food production systems. Int. J. Food Microbiol. 187:57-72.

Broadway, P. R., J. A. Carroll, J. C. Brooks, J. R. Donaldson, N. C. Burdick-Sanchez, T. B. Schmidt, T. R. Brown, and T. R. Callaway. 2014. Salmonella transfer to the lymph nodes and synovial fluid of experimentally orally inoculated swine. Agric. Food Anal. Bacteriol. 5:6-14.

Grilli, E., R. Bari, A. Piva, T. S. Edrington, D. W. Pitta, W. E. Pinchak, D. J. Nisbet, and T. R. Callaway. 2014. Organic acid blend with pure botanical product treatment reduces E. coli and Salmonella populations in pure culture and in in vitro mixed ruminal microorganism fermentations. Foodborne Path. Dis. 12:56-61

Broadway, P. R. J. A. Carroll, and T. R. Callaway. 2014. Antibiotic use in livestock production. Agric. Food Anal. Bacteriol. 4:76-85.

Broadway, P. R. J. A. Carroll, and T. R. Callaway. 2014. Alternative antimicrobial supplements that positively impact animal health and food safety. Agric. Food Anal. Bacteriol. 4:109-121.

Callaway, T. R., T. S. Edrington and D. J. Nisbet. 2014. Ecological and dietary impactors of foodborne pathogen prevalence and methods to reduce colonization in cattle. J. Anim. Sci. 92:7308-7342.

Callaway, T. R. and T. G. Sheridan. 2015. A smarter arrow now available in the food safety quiver. Procs. Nat. Acad. Sci. (USA) 112:12230-12231.

Grilli, E. F. Foresti, B. Tugnoli, M. Fustini, M. G. Zanoni, P. Pasquali, T. R. Callaway, A. Piva, and G. L. Alborali. 2015. Microencapsulated sorbic acid and pure botanicals affect Salmonella Typhimurium shedding in pigs: a close-up look from weaning to slaughter in controlled and field conditions. Foodborne Path. Dis. 12:813-819.

Munns, K. D., L. B. Selinger, K. Stanford, T. R. Callaway and T. A. McAllister. 2015. New Perspectives on Super-Shedding of Escherichia coli O157:H7 by Feedlot Cattle. Foodborne Path. Dis. 12:89-103.

Tellez, G. A. Laukova, J. D. Latorre, X. Hernandez-Velasco, B. M. Hargis and T. R. Callaway. 2015. Food-producing animals and their health in relation to human health. Microb. Ecol. Health Dis. 26:25876-25886.

Cribbs, J. T., T.R. Young, M.A. Jennings, N.C. Burdick, J.A. Carroll, T.R. Callaway, T.B. Schmidt, B.J. Johnson, R.J. Rathmann. 2015. Dehydrated citrus pulp alters feedlot performance of crossbred heifers during the receiving period and modulates serum metabolite concentrations pre- and post-endotoxin challenge. J. Anim. Sci. 93:5791-5800.

Buntyn, J. O., T. B. Schmidt, D. J. Nisbet and T. R. Callaway. 2016. The role of direct-fed microbials in conventional livestock production. Ann. Rev. Anim. Biosci. 4:335-355.

Beier, R. C., E. Franz, J. L. Bono, R. E. Mandrell, P. M. Fratamico, T. R. Callaway, K. Andrews, T. L. Poole, T. L. Crippen, C. L. Sheffield, R. C. Anderson, and D. J. Nisbet. 2016. Disinfectant and antimicrobial susceptibility profiles of the big six non-O157 Shiga toxin-producing Escherichia coli from food animals and humans. J. Food Prot. 79:1355-1370.

Conrad, C. C., K. Stanford, C. Narvaez, T. R. Callaway, and T. A. McAllister. 2017. Farms, fairs, and petting zoos: Animal contact as a source of zoonotic enteric disease. Foodborne Path. Dis. 14:59-73.

Bell, N. L., R. C. Anderson, T. R. Callaway, M. O. Franco, J. E. Sawyer, and T. A. Wickersham. 2017. Effect of monensin inclusion on intake, digestion, and ruminal fermentation parameters in Bos indicus and Bos taurus steers consuming bermudagrass hay. J. Anim. Sci. 95:2736-2746.

Bell, N. L., T. R. Callaway, R. C. Anderson, M. O. Franco, J. E. Sawyer, and T. A. Wickersham. 2017. Effect of monensin withdrawal on intake, digestion, and ruminal fermentation parameters in Bos indicus and Bos taurus steers consuming bermudagrass hay. 95:2747-2757.

Poole, T. L., T. R. Callaway, K. N. Norman, H. M. Scott, G. H. Loneragan, S. A. Ison, R. C. Beier, D. M. Harhay, B. Norby, and D. J. Nisbet. 2017. Transferability of antimicrobial resistance from multidrug-resistant Escherichia coli isolated from cattle in the United States to Escherichia coli or Salmonella Newport recipients. J. Global Antimicrob. Resist. S2213-7165(17)30146-7. doi: 10.1016/j.jgar.2017.08.001. [Epub ahead of print].