Josie Garner, PhD University of Melbourne

Current Role: Research Scientist, Agriculture Victoria

PhD Research: The physiology and functional genomics of the heats stress response in dairy cattle

Context

Thermal stress experienced by dairy cattle, can be one of the greatest limitations on production efficiency and animal health. In the Australian climate the effects of heat stress causes millions of dollars in lost production every year. With the increase in the frequency and severity of heat events in the temperate climate dairying regions of Australia, the need to identify and breed heat tolerant dairy cattle is one of the most important traits.

My PhD research examined the physiological, functional genomics and metabolic responses of Australian dairy cows to experimentally induced heat stress which replicates the moderate short-term heat events observed in the temperate climates of Australia. I also conducted an experiment validating genomic selection for heat tolerance within the Holstein Friesian breed.

Science outcomes

Genome wide DNA marker based prediction (genomic predictions) of heat tolerance from previous research were validated, as the genomically predicted heat tolerant cows during experimentally induced heat stress maintained milk production and feed intake to a higher level, and had lower core body temperature than genomically heat susceptible cows. Additionally, my research demonstrates the susceptibility to heat stress of dairy cows which are adapted to a temperate climate. The experiment also described the recovery period after exposure to a heat challenge, which identified that there was a delay between the return to normal feed intake and milk production. This indicates that there may be a period of metabolic recovery required post heat exposure. During my PhD I identified novel differences in global gene expression changes in vivo in the blood of genomically selected heat tolerant and heat susceptible cows. Biological pathways that were consistently affected by heat stress throughout my research were lipid metabolism, carbohydrate metabolism, apoptosis and protein folding, and a candidate list of genes were identified for further targeted research.

Industry impact

This PhD research highlights the important validation of genomic selection for heat tolerance in dairy cattle. This is a world first achievement and provides key information for the Australian dairy industry to develop a commercially available breeding value for heat tolerance, which has been released to and adopted by the industry.

Education program

Being part of the DairyBio education program provided opportunities for personal and professional development. Particular highlights were the support and friendship of fellow PhD students during my time working in the Animal Molecular Genetics lab at AgriBio, as well as learning about the broader science happening within DairyBio.