About Me
I'm a Postdoctoral Research Associate at Cornell University working at the intersection of animal nutrition, climate-smart agriculture, and precision technology. My work focuses on advancing sustainable livestock systems that promote food security, economic resilience, and environmental stewardship.
Born and raised in Honolulu, Hawai‘i, I earned my B.S. in Animal Science from the University of Hawai‘i. As an undergraduate, I contributed to research on low-stress cattle handling, disease management, and shipping stress in beef cattle. I later led a USDA Children’s Healthy Living Program project in Micronesia, investigating the public health and ecological impacts of free-roaming dogs. Following this, I transitioned into pharmacokinetic research supporting novel drug development for Cryptosporidium parvum, a pathogen impacting calves and children in low- and middle-income countries. I was later promoted to research manager and coordinated first-in-human clinical trial logistics in Zambia.
In 2019, I joined Dr. Tom Overton’s lab at Cornell University, earning my Ph.D. in Dairy Cattle Nutrition with minors in Epidemiology and Global Development. My research interests evolved to focus on nutritional strategies to prevent and manage metabolic diseases in dairy cattle.
Currently, I work with Drs. Kristan Reed and Daryl Nydam as part of the Ruminant Farm Systems (RuFaS). I also continue to collaborate with Dr. Francisco Leal Yepes and his laboratory, Precision Livestock Health (PLH). I serve as a project team leader and subject matter expert, supporting research that integrates advanced sensing technologies to mitigate greenhouse gas emissions in dairy production. Our interdisciplinary team includes software engineers, agricultural scientists, and systems modelers working together to address complex challenges in animal agriculture.
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Graef G.M., A.M. Valeria, V. Ramirez, A. Zapata-Salazar, A. Ceballos, T.R. Overton, F.A. Leal-Yepes. Analysis of calcium status of multiparous Holstein cows and its impact on health and production of Colombian dairy farms. JDS Commun. https://doi.org/10.3168/jdsc.2025-0945.
Graef G.M., A. Sipka, S. Tompkins, C.R. Seely, T.R. Overton. Associations between peripartum calcium dynamics and inflammation status in multiparous Holstein cows. J Dairy Sci. https://doi.org/10.3168/jds.2024-25979.
*Graef, G. M., Kerwin, A. L., Ferro, L. N., Ordaz-Puga, S., Ryan, C. M., Westhoff, T. A., ... & Overton, T. R. (2025). Effect of prepartum dietary cation-anion difference strategy and level of dietary calcium on postpartum blood calcium status and milk production of multiparous Holstein cows. J Dairy Sci. https://doi.org/10.3168/jds.2024-25783.
Kerwin, A. L., Graef, G. M., Ryan, C. M., Ferro, L., Puga, S. O., Westhoff, T. A., ... & Overton, T. R. (2023). Effect of replacing a portion of inorganic chloride trace minerals with trace mineral amino acid complexes. J Dairy Sci, 106(9), 6128-6145.
Graef G, Hurst NJ, Kidder L, Sy TL, Goodman LB, Preston WD, et al. (2018) Impact of confinement housing on study end-points in the calf model of cryptosporidiosis. PLoS Negl Trop Dis 12(4). https://doi.org/10.1371/journal.pntd.0006295.
*J Dairy Sci Editors Choice Award
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3MT Spotlight presentation G. Graef, A.M. Valencia, V.R. Cardona, A. Ceballos-Marquez, T.R. Overton, F.A. Leal-Yepes. Analysis of calcium status of multiparous Holstein cows and its impact on milk production in pasture dairies. Proceedings of American Dairy Science Association; 2024, June 16-19; West Palm Beach, Florida.
Graef G.M., S. Tompkins, T.R. Overton. Association of subclinical hypocalcemia classification with blood haptoglobin concentrations during the periparturient period. Proceedings of American Dairy Science Association; 2024, June 16-19; West Palm Beach, Florida.
Graef, G. (2024). Dairying in Colombia: Grazing cows contending with subclinical hypocalcemia.
Graef G.M., A.L. Kerwin, L.N. Ferro, S. Ordaz-Puga, C.M. Ryan, T.A. Westhoff, D.M. Barbano, K.M. Glosson, K.P. Zanzalari, J.D. Chapman, T.R. Overton. Effect of prepartum dietary cation-anion difference (DCAD) strategy and level of dietary calcium on peripartum mineral status of multiparous Holstein cows. Proceedings of American Dairy Science Association; 2022, June 19-22; Kansas City, Missouri. Abstract nr 86419.
Graef G.M., A.L. Kerwin, L.N. Ferro, S. Ordaz-Puga, C.M. Ryan, T.A. Westhoff, D.M. Barbano, K.M. Glosson, K.P. Zanzalari, J.D. Chapman, T.R. Overton. Effect of prepartum dietary cation-anion difference (DCAD) strategy and level of dietary calcium on peripartum performance of multiparous Holstein cows. Proceedings of American Dairy Science Association; 2022, June 19-22; Kansas City, Missouri. Abstract nr 86419.
L.N. Ferro, A.L Kerwin, C.M. Ryan, G.M. Graef, T.M. Nelson, H. Green, F. Yang, M. Embree, D.M. Barbano, T.R Overton. Effects of a novel direct fed microbial feed additive on performance of lactating Holstein dairy cows. Proceedings of American Dairy Science Association; 2022, June 19-22; Kansas City, Missouri.
T. Nelson, A. Kerwin, L. Ferro, C. Ryan, G.M. Graef, T. Westhoff, A. Sipka, S. Mann, D. Barbano, B. Stone, I. Yoon, T. Overton. Relationships of blood-based indices of liver health during the transition period with performance and health outcomes. Proceedings of American Dairy Science Association; 2022, June 19-22; Kansas City, Missouri.
Graef G.M., A.L. Kerwin, L.N. Ferro, S. Ordaz-Puga, C.M. Ryan, T.A. Westhoff, D.M. Barbano, K.M. Glosson, K.P. Zanzalari, J.D. Chapman, D.J. McLean, T.R. Overton. Effect of prepartum Dietary Cation-Anion Difference strategy and level of dietary calcium on postpartum Ca status and performance of multiparous Holstein cows. Proceedings of American Dairy Science Association; 2021, July 11-14; Louisville, Kentucky. Abstract nr 84443.
Graef G.M., A.L. Kerwin, L.N. Ferro, S. Ordaz-Puga, C.M. Ryan, T.A. Westhoff, D.M. Barbano, K.M. Glosson, K.P. Zanzalari, J.D. Chapman, D.J. McLean, T.R. Overton. Effect of prepartum Dietary Cation-Anion Difference strategy and level of dietary calcium on postpartum Ca status and performance of multiparous Holstein cows. Proceedings Cornell Nutrition Conference; 2021, October 19-21; Syracuse, NY.
