Project code: D-95-18

Project Summary

Fresh grass is the cheapest feed source available for ruminant animals. It is Northern Ireland’s competitive advantage to grow grass the majority of the year and this advantage must be optimised to ensure maximum efficiency within our dairy industry.

In Northern Ireland, grazing remains a major component in dairy cow diets during the spring and summer months and can significantly influence animal performance and profit during this period. Individual animal grass DMI and consequently performance at pasture is influenced by a range of factors including: the animals’ genetic potential, parity, sward nutritive value, plant density, herbage allowance and pasture allocation strategies. Grass allocation strategies and in particular grass allocation frequency has been found to significantly affect grass DMI in dairy cattle (Walton et al., 1981).

A recent interest has been expressed in 36-hour allocation periods for grazing dairy cattle to support better performance of individual dairy cows. Through this approach it offers animals two periods of high grass allocation and one period of restricted grass allocation, reducing the frequency of potential pasture restriction. This approach is considered by some farmers to support the performance of subordinate and parity one animals. However, current research on individual variations in cattle performance and grazing behaviour at pasture is limited. 

Project Outline

The project will investigate the effect of frequency of fresh pasture allocation on individual animal performance and herbage utilisation in dairy cattle and will be conducted using the dairy research herd at AFBI, Hillsborough utilising the resources on the Precision Grassland Platform, part of the Centre of Innovation Excellence in Livestock. Dairy cows will be split into three balanced groups taking account of; parity, genetic merit, calving date, current pregnancy status, milk yield and live weight.  

Allocated a frequency of fresh pasture: 

  • 12 hour allocation of fresh pasture,
  • 24 hour allocation of fresh pasture,
  • 36 hour allocation of fresh pasture.


The proposed project will run from April to August, collecting multiple grass and animal measurements including: 

  • Grass quality
  • Grass quantity
  • Milk yield 
  • Milk quality
  • Grazing behaviour
  • Cow activity
  • Body condition score (BCS)
  • Body weight (BW)
  • Locomotion 
  • Individual animal DMI through the n-alkane technique.



The objectives of the proposed project are as follows:

  1. Evaluate the impact frequency of pasture allocation has on individual animal DMI.
  2. Evaluate the effect frequency of allocation has on individual animal performance and health.
  3. Evaluate the effect frequency of allocation has on grass utilisation.
  4. Evaluate the effect of the interaction of parity and frequency of allocation on individual animal DMI.
  5. Evaluate the effect of the interaction of parity and frequency of allocation on grazing behaviour.

In addition, the information collected in this study will be employed in a subsequent study, investigating the potential of precision technologies to measure individual DMI of dairy cattle at pasture.