| Summary: | Production and consumption of ruminant products is partly being held accountable for the increasing global challenges of human health and climate change. Also, increasing demand for food, feed and fuel is placing growing pressure on land availability. One area under investigation in response to these challenges is fatty acid content of forages. This thesis sets out to investigate the variation and relationships between fatty acids, lipids, chlorophyll and other nutritional aspects of perennial ryegrass. Additionally, it will investigate alternative methods to predict fatty acids in forage. The core experiment involved twenty-four genotypes from two perennial ryegrass populations. Fatty acids were found to increase in leaf material during a growing season. Genotype differences in fatty acid content and composition were found which were broadly consistent across the growing season. Fatty acids correlated positively with crude protein but negatively with water-soluble carbohydrates. A positive and consistent relationship was found between chlorophyll and fatty acids across the growing season. The use of a chlorophyll meter to estimate fatty acid content did not perform very well, due to poor relationships with in vitro chlorophyll, however near-infrared reflectance and Fourier-transform mid-infrared spectroscopy had acceptable prediction accuracies for use as a screening tool. The accuracies of these prediction methods could be improved with further development using larger datasets. Investigation of the lipid composition revealed that galactolipid proportion was the main contributor to increased total fatty acid content in the high FA genotypes. While phospholipid proportion was minimally affected and neutral lipid negatively affected by increased total fatty acid content. Further work is needed to determine the underlying genetic control of fatty acid and lipid synthesis in perennial ryegrass. Additionally, a great deal more research is needed to establish environmental and genetic effects on lipid composition of forages.
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