Meet the Team

Dr. Todd R. Callaway, PhD

Dr. Todd R. Callaway is a ruminant microbiologist whose research focuses on the role of ruminal and intestinal microbes in the nutrition, health, productivity, and food safety of cattle and other food animals. His work is centered on unravelling the microbial ecology of the gut and understanding how diet, environmental factors, microbial physiology, and management can alter microbial populations and host responses.

Dr. Callaway’s research has focused on foodborne pathogenic bacterial populations, antimicrobial resistance transfer, rumen microbial ecology, microbial physiology, and intervention strategies to improve food safety and animal production. His current work at UGA continues to examine how manipulation of ruminal and intestinal microbes can improve production efficiency, animal health, sustainability, and profitability on the farm.

Hunter G. Perez, M.S.

Hunter G. Perez is originally from Palm Coast, Florida, and received his Bachelor of Science in Animal Science from Berry College in Rome, Georgia, in 2023. He completed his M.S. in Animal and Dairy Science at the University of Georgia from 2023 to 2025 and began his Ph.D. in 2025. Hunter is advised by Dr. Todd Callaway and Dr. Francis Fluharty.

Hunter’s research interests include ruminant nutrition, rumen microbiology, feedlot management, food safety, and applied beef cattle production. His master’s research evaluated how forage quality affects E. coli and coliform shedding, rumen fermentation, animal performance, methane emissions, and the ruminal and fecal microbiomes in beef cattle. This work reflects his broader interest in understanding how diet influences the microbial population of the gastrointestinal tract and how unravelling the microbial ecology of the rumen can provide insight into ruminant health, productivity, and food safety.

Within his PhD, Hunter’s research continues to connect ruminant nutrition, microbial ecology, and applied cattle management. His doctoral work is focused on beef cattle nutrition and microbiology, with interests in how animal genetics, diet, management, and environmental stressors may influence ruminal and intestinal microbial populations, animal performance, feed efficiency, and food safety outcomes.

In addition to his research, Hunter assists with lab and project coordination, undergraduate mentorship, student training, extension and outreach activities, and teaching within the Department of Animal and Dairy Science.

Donald “Donnie” Holupka

Donald “Donnie” Holupka is a native of Hillsboro, Missouri, and received his Bachelor of Science in Animal Science from the University of Nebraska-Lincoln in the spring of 2024. Donnie began his M.S. program in Animal and Dairy Science at the University of Georgia in 2024 under the advisement of Dr. Todd Callaway and Dr. Francis Fluharty.

Donnie’s research interests include ruminant nutrition, methane reduction, beef cattle production, grazing systems, and the relationship between metabolites and methane production. His master’s research is focused on methane reduction in beef cattle, with an emphasis on understanding metabolites and methane production in southeastern grazing systems. Donnie is also investigating nutritional mitigation strategies to reduce methane production in beef cattle background setting to reduce energetic loss due to methane production.

In addition to his research, Donnie assists with coaching the livestock judging team within the Department of Animal and Dairy Science.

Allison Harikkala

Allison Harikkala was raised in Greenville, Wisconsin, and received her Bachelor of Science in Animal Science from Berry College in 2026. She was accepted into the dual DVM/Ph.D. program, also known as the Veterinary Medical Scientist Training Program (VMSTP) through the University of Georgia College of Veterinary Medicine. As part of this dual-degree program, Allison chose the Department of Animal and Dairy Science to pursue her Ph.D. training. Allison is advised by Dr. Todd Callaway and Dr. Francis Fluharty.

Allison is interested in gaining a deeper understanding of food animal production through hands-on research, animal-based experience, and applied scientific training. Her interests include food animal health, livestock production systems, and the connection between veterinary medicine, animal agriculture, and research.

Austin Jones

Austin Jones is from Tiger, Georgia, in Rabun County. He received his Bachelor of Science in Animal Bioscience from the University of Georgia and will be continuing in the Department of Animal and Dairy Science as a master’s student in the Ruminant Nutrition and Gut Microbiology Lab.

Austin previously worked with the lab as an undergraduate research assistant, where he gained experience supporting animal research, sample collection, laboratory work, and project activities related to ruminant nutrition and gut microbiology. His interests include applied animal science, food animal production, and understanding how nutrition and management influence animal health and productivity.