The development of near infrared calibrations for assessing grass herbage quality R. Mellon, S. Sharma, D Johnson and H Fletcher* Department of Applied Plant Science, The Queen’s University of Belfast and Applied Plant Science Division, Department of Agriculture for N. Ireland, Newforge lane, Belfast, BT9 5PX, UK BACKGROUND The main selection parameters used by forage grass (rye and Italian ryegrass) breeders are dry-matter yield, seasonal growth, persistency, disease resistance, heading date, and heading. These characteristics can all be identified usually in the segregating F2 population, however characteristics such as soluble carbohydrate level, protein, lipid and digestibility cannot be identified. This is aimed at introducing a quantitative selection process for characterisation of herbage quality e.g. disease resistance or susceptibility, dry matter digestibility (DMD), water-soluble carbohydrates and fibre fractions. METHOD The changes in fibre fractions, associated components and digestibility of a number of grass clones at different growth stages are being assessed extensively using biochemical, and thermal methods. This will provide a database of the major changes including disease incidence, taking place during a growing season. F2 progeny susceptible to crown rust susceptible and resistant leaves showing rust pustules F2 tussocks Vis-NIR spectra of fresh grass samples - F2 genotypes. NIRS calibration (r2 = 0.87) for DMD CONCLUSION NIRS calibration for assessing DMD of grass (cut 1-5) as determined by pepsin-cellulase assay has been developed and susceptibility/resistance to crown rust can also be classified from the vis-NIR spectra. Further work is in progress to generate additional calibrations for other key parameters and also to expand the database .