An investigation into the grazing efficiency of perennial ryegrass varieties

Tomas Tubritt, Luc Delaby, Trevor Gilliland, Michael O’Donovan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
50 Downloads (Pure)


The objective of this study was to compare the grazing efficiency of 30 perennial ryegrass varieties, differing in ploidy and heading date. Plots were grazed by lactating dairy cows and managed under a rotational grazing system with 19 grazing events occurring over two years. Pre-grazing and post-grazing compressed sward heights were measured with a rising plate meter. A mixed model was used to predict the post-grazing sward height of each variety based on year, grazing event, block and pre-grazing sward height. Residual grazed height (RGH) was derived as the difference between the actual and predicted post-grazing sward height and was used as the measure of grazing efficiency. Negative RGH values indicated that the actual herbage removed was greater than that predicted and so indicated a superior grazing efficiency. Varieties differed in their level of grazing efficiency (p <.001), with RGH values ranging from −0.38 to +0.34 cm. Tetraploid varieties exhibited significantly greater grazing efficiency performance than diploids (p <.001), with average RGH values of −0.13 and +0.13 cm respectively. A significant difference in grazing efficiency was found among recommended perennial ryegrass varieties that are not being recorded by mechanically harvested simulated grazing protocols. A variety reappraisal that included grazing efficiency could identify varieties capable of improving on-farm livestock productivity from grass.

Original languageEnglish
Pages (from-to)253-265
Number of pages13
JournalGrass and Forage Science
Issue number3
Early online date18 Aug 2020
Publication statusPublished - 01 Sept 2020

Bibliographical note

Publisher Copyright:
© 2020 The Authors. Grass and Forage Science published by John Wiley & Sons Ltd.

Copyright 2020 Elsevier B.V., All rights reserved.


  • grazing efficiency
  • Lolium perenne L.
  • post-grazing sward height
  • residual grazed height
  • variety

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Management, Monitoring, Policy and Law


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