Congratulations to AAOCS member [soon to be Dr.] Leonie Walter

AAOCS student member, Leonie Walter, submitted her Ph.D. thesis entitled “Understanding small and large milk fat globule phenotype variation in dairy cows through milk lipidomic characterisation” in August 2019 and graduated earlier this year. Her Ph.D. was conducted through the Faculty of Veterinary and Agricultural Science at the University of Melbourne in conjunction with CSIRO, under the supervision of Professor Brian Leury, Dr. Richard Fry and Dr. Amy Logan.

Milk fat globules (MFGs) are spherical structures comprising a neutral lipid core that is surrounded by a three-layer membrane. Individual variation in MFG size is observed within dairy herds and, if selected for thorough breeding programs, could be exploited for a more targeted milk production for specific technological streams. 

Her thesis’s initial experiment aimed to determine how much the average MFG size is affected by on-farm and animal-related factors within a herd subjected to the same diet and environmental conditions: Walter, Leonie, Sue Finch, Brendan Cullen, Richard Fry, Amy Logan and Brian J. Leury. "The effect of physiological state, milk production traits and environmental conditions on milk fat globule size in cow's milk." Journal of Dairy Research 86, no. 4 (2019): 454-460.

Based on the data collected for the first experimental chapter, cows were selected for the second and third experiment, which aimed to characterise the small and large MFG phenotypes through an in-depth lipidomics analysis. This analysis included the characterisation of the fatty acid profile of the MFG core by gas chromatography and the identification of the whole milk lipidome through targeted liquid chromatography-tandem mass spectrometry: Walter, L., P. Shrestha, R. Fry, B. J. Leury, and A. Logan. "Lipid metabolic differences in cows producing small or large milk fat globules: Fatty acid origin and degree of saturation." Journal of Dairy Science 103, no. 2 (2020): 1920-1930.

The third experiment, conducted in conjunction with Metabolomics Australia, presents the most extensive milk lipidomic analysis in the literature to date, with 301 detected lipid species. The results also revealed, for the first time, a potential role for ether phosphatidylethanolamine in the regulation of MFG size, showing a higher relative abundance of ether phosphatidylethanolamine in the milk from cows that tended to produce larger MFGs: Walter, Leonie, Vinod K. Narayana, Richard Fry, Amy Logan, Dedreia Tull and Brian Leury. "Milk fat globule size development in the mammary epithelial cell: a potential role for ether phosphatidylethanolamine." Scientific Reports 10, no. 1 (2020): 1-13.

The final experiment developed an in vitro model using cells purified from raw milk and grown on permeable membrane supports: Walter, Leonie, Richard Fry, Amy Logan and Brian J. Leury. "Investigation on the suitability of milk-derived primary bovine mammary epithelial cells grown on permeable membrane supports as an in vitro model for lactation." In Vitro Cellular & Developmental Biology. Animal (2020).

“Leonie, it has been an absolute pleasure to co-supervise your Ph.D., where I was able to watch you develop into a truly gifted and exemplary scientist. A huge congratulations for all that you have achieved, and I wish you all the very best for this next phase of your career” — Dr. Amy Logan (AAOCS member and outgoing Treasurer for the AAOCS).

And from all of us here at AAOCS, congratulations, Leonie! 

Other Ph.D. students who are graduating, we would love to hear from you or your supervisors to help you celebrate! Contact your Division of the AOCS Communication Specialist, Katrina Gaffney.