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Improving evaluation and selection criteria of ryegrass varieties by linking phenotypic from research and commercial farm environments Nicky Byrne (20806034) PUREID: 498988616 Herbage utilisation is of primary importance to grassland fanners due to its strong association with profit, yet it is not assessed in routine grass evaluations and is of low breeder priority. To assess herbage utilisation, evaluation programmes would need to be conducted under animal grazing, which is complex and prohibitively expensive. Currently, grass variety evaluations are conducted under simulated grazing, cut-plot environments, which differ greatly to those experienced on commercial farms where varieties are exposed to higher levels of stress from grazing animals. Plot-based testing provides poor direction to breeders in the development of varieties for grazing systems, focusing heavily on herbage production. The objective of this thesis was to influence the development of elite grazing varieties with improved grazing efficiency, through improvements in grass evaluation strategies and identifying plant and sward characteristics which influence grazing efficiency and productivity of grass varieties.<br><br>When varieties were evaluated on commercial grassland farms throughout Ireland, variety was found not to significantly influence total herbage production. Varieties, however were found to differ in their suitability for intensive grazing, with variety significantly influencing the level and quality of grazed herbage produced. When assessed in animal grazed plots, tetraploid varieties were found to have significantly better grazing efficiency than diploids. This study identified increased dry matter digestibility, free leaf lamina and tiller mass as key selection criteria to develop improved grazing varieties, as they were found to significantly improve grazing efficiency. Under simulated grazing, perennial ryegrass was found to be better suited to grazing systems than hybrid ryegrass varieties tested, as it maintained high herbage quality throughout the year and had better yield stability. This study also demonstrated that annual herbage production was not limited by sward density.<br><br>This thesis provides evidence that varieties differ greatly in their suitability for grazing, due to differences in their structural and chemical characteristics. However, to assess and to encourage breeders to prioritise these characteristics, evaluation programmes need to change by assessing the interaction of plant and animal. 2026-10-01T16:49:29Z Text Thesis 10.17034/32637600.v1 https://figshare.com/articles/thesis/Improving_evaluation_and_selection_criteria_of_ryegrass_varieties_by_linking_phenotypic_from_research_and_commercial_farm_environments/32637600 All Rights Reserved