Exploring the application of Rapid Evaporative Ionisation Mass Spectrometry (REIMS) to bovine health monitoring and milk quality analysis

Research has previously demonstrated that REIMS offers a high-throughput platform for the rapid and reliable identification of isolates of bacteria and fungi. In comparison to matrix assisted laser desorption ionisation time of flight mass spectrometry (MALDI-ToF), which is available commercially, REIMS-based methods do not require any preparatory procedures or laborious cell extractions.<br>Bovine mastitis continues to be an extremely prevalent infection in cattle and has a significant financial impact on the dairy sector worldwide.

Mastitis damages the glandular tissue of the udder and alters the physical, chemical, and microbiological composition of the milk, which interferes with both the quantity and quality of milk produced. It causes several negative impacts, including lower yields of milk, higher rates of culling and treatment expenses, and an increased risk of dying from serious ailments caused. Additionally, some udder infections — such as Staphylococcus aureus — have an<br>[ 2 ]<br>influence on food safety by releasing toxins that may result in food poisoning.

There are currently more than 140 potentially pathogenic organisms that have been identified as sources of bovine mastitis. Depending on the type of organism involved, the illness is classified into the following categories: bacterial, mycotic/fungal/algal, mycoplasmal, or nocardial mastitis. Microbes, the host, and the environment are each involved in the multifactorial disease referred to as mastitis.

Epidemiology classifies mastitis as either environmental or contagious.<br>The primary objective of this research project is to utilise REIMS for the analysis of milk quality and the monitoring of bovine health. As part of the bovine health monitoring program, project one focused on comparing how the milking procedure and animal care affect the health and milk produced by milking cows. Milk samples from the same dairy cows were collected for one year on four different farms.

REIMS was then applied to compare the milk qualities. This study has successfully used REIMS to identify how the overall care and milking procedure can influence the quality of the milk and bovine health.<br>The second primary objective of this project was to use REIMS to identify the bacteria that were grown from milk samples from the selected cows on various types of agar and incubated in different conditions. Each milk sample was plated onto the agar dishes to grow bacterial isolates, which were subsequently frozen and stored.

Once the project was completed, REIMS was successfully applied to identify the bacterial isolates as a group. In conclusion this research project has shown the benefits of REIMS for rapid identification of bacteria causing bovine mastitis.<br>The third project, conducted in collaboration with Chestnutt Farm, examined the possible advantages of the farm's chosen on-site pasteurisation technique on the overall quality of milk using REIMS technology.

The results have demonstrated the benefits of the on-site pasteurisation process, which significantly lowers the microbial load in comparison to raw milk. However, there is no variation<br>[ 3 ]<br>between the raw and on-site pasteurised milk's composition. In conclusion, the on-site technique produces nutritious, healthful milk without compromising the overall quality of the milk.<br>The final experiment examined the characteristics and quality of semen samples taken from bulls of the five most common dairy cow breeds.

As the first publication to apply REIMS to semen samples, this project first optimised REIMS for semen sample analysis before selecting and assessing a wide range of traits displayed by the chosen breeds. In summary, this study has been utilised to identify trait differences across breeds and the ways in which liquid nitrogen may influence the characteristics of the semen sample.<br><br><i>Thesis embargoed until 31st July 2030.</i>