Metabolomics for biomarker discovery: improving the health, performance and longevity of dairy cows by non-invasively detecting rumen pH

"Metabolomics for biomarker discovery: improving the health, performance and longevity of dairy cows by non-invasively detecting rumen pH

Nutritional demands are high for the modern dairy cow during lactation. To meet these requirements for energy and metabolisable protein, it is common to feed large quantities of concentrates, particularly during early and mid-lactation (Zebeli et al., 2012). This scenario is very much a double-edged sword, these grain-rich concentrates are not only palatable but rapidly ferment in the rumen, leading to the rapid production of large quantities of short-chain fatty acids (SCFA; Tayyab et al., 2022; Johnson et al., 2023). Resulting intermittent drops in ruminal pH gradually impairs rumen function, and if these are severe, prolonged, and frequent enough, they lead to a condition known as subacute ruminal acidosis (SARA; Dirksen, 1985). The mean prevalence of SARA on UK dairy farms is estimated to be approximately 26.2% (Atkinson, 2014), with the condition often resulting in lower fibre digestibility, reduced intakes and milk yield, increased culling, and a higher carbon cost per litre of milk. Economically there is an estimated loss of approximately £340 per cow per lactation (Stone, 1999). Despite the importance to dairy cow health and welfare, diagnosis of the disease is problematic, requiring invasive techniques. Metabolomics is a technique that utilises advanced analytical chemistry to provide researchers with a more complete picture of the animal's phenotype at the metabolic level. The technique is of particular interest because it can be utilised to identify novel metabolites (biomarkers) of disease. Subsequently, the aim of this PhD is to profile metabolic pathways and discover metabolomic biomarkers that can be used to diagnose SARA in a non-invasive manner, thereby allowing diets to be adjusted to treat or prevent the disease."