Grass Quality: What it is and why it drives sward utilisation

Tuesday 07.05.2019 , News

For intensive grazing systems, grass quality is the most important trait to maximise animal performance. Grass quality will drive animal performance, with a 1-unit increase in DMD increasing milk yield by 0.25 litres/cow/day.

The Teagasc Pasture Profit Index (PPI) demonstrates a difference of €94 per ha/year, between the highest performing variety for quality (AberGain; +€56 per ha/year) compared to the lowest performing variety for quality (Majestic; -€38 per ha/year).

Sward Palatability

It is well known that higher quality grasses are more palatable to animals, so intake will be higher and sward utilisation will be better. Selecting grasses with low quality values will make it more difficult for the animal to graze the sward, therefore both sward utilisation and animal performance will be negatively affected.

Diploid or Tetraploid Grasses

Diploid grass varieties by their nature are lower in quality compared to tetraploids, due to their higher content of cell wall to cell contents. Diploids help create a dense sward, so there is value in including them in your grazing mixture. However, ensuring you have the correct proportion of diploid to tetraploid grasses (approx. 50:50) is important. In addition, there is a big difference in the quality of diploid grasses. On the 2019 PPI, there are 9 late diploid grass varieties and only 2 of these varieties (AberChoice and Drumbo) have a positive value for quality on the Index. Choosing diploids with higher quality values will help ensure you have a more palatable grass mixture which will have a positive effect on animal intake and animal performance.

Diploid (2n)Tetraploid (4n)
2 sets of chromosomes

4 sets of chromosome

Larger cell size & higher ratio of cell contents (soluble carbohydrates) : cell wall (fibre)

Lower quality (DMD)Higher quality (DMD) = more palatable = greater intakes
Higher DM content (% DM)Lower DM %
More densely tilleredMore open – more susceptible to poaching

grass quality field

Grass Mixtures

For intensive grazing mixtures, ensuring all varieties in the mix have a positive value for quality is important to maximise animal performance from the grazed sward. Selecting lower quality varieties in a mix will reduce animal performance and hence, profit. Before you buy a bag of grass seed, do some research yourself. Have a look at the PPI and how varieties perform across all traits, but in particular the quality trait and use this as the basis of selecting your grass seed mix.

View 2019 Pasture Profit Index