The pasture profit index (PPI) is a variety selection tool used to identify the best perennial ryegrass varieties for Irish farming systems.

Varieties are assessed over a number of traits including spring, summer and autumn herbage yield, quality, silage yield, persistency and grazing utilisation.

Variety performance for a trait is expressed as a euro (€) value, which represents the additional net profit per hectare per year that can be expected by sowing that variety.

Higher values for a trait indicate higher performance. The total PPI of a variety is the sum of its performance in each trait that gives an indication of its overall merit.

The PPI is produced from data collected by the Department of Agriculture, Food and the Marine’s recommended list trials team and from grazing studies conducted at Teagasc Moorepark.

In total, there are 36 varieties listed in the Irish recommended list in 2024. While all varieties have their merits, the PPI is a selection tool that allows comparison between varieties based on their total merit and/or based on selected trait(s).

Every grass variety has some positives and weaknesses, but the objective of the PPI is to rank the varieties specifically on their individual traits and then rank them on the total index.

This is the first year where three new varieties have PPI values above €200 at recommendation. Galgorm (€266), Aberspey (€240) and Tollymore (€225) all have broken this threshold, which clearly shows that grass breeders and wholesale companies are responding to the challenges set out in the PPI.

The PPI was introduced to the Irish grassland industry in 2013, and 11 years on, there are clear indications that the grass breeding community is now focused on bringing varieties to market to meet farmer requirements.

For example, Galgorm is a new variety entering the PPI in 2024, achieving the top spot with a total PPI value of €266. Galgorm’s total PPI value can be divided up into spring yield (€60), summer yield (€66), autumn yield (€67), quality (€25) and silage (€47).

It is also deemed persistent and has a one-star score for grazing utilisation.

Aberspey is ranked second (€240) and Tollymore is ranked fifth (€225).

Both of these varieties are intermediate-heading tetraploids with good growth characteristics, high quality and both have grazing utilisation ratings of four and five stars, respectively.

Choosing the right variety to suit your farm type

In general, we see the continued trend of tetraploid varieties excelling in terms of grazing efficiency.

Farmers reseeding paddocks destined for intensive grazing should aim to include an increased proportion of high grazing utilisation varieties in their mixtures, while optimising mixture quality also.

When reviewing grass seed mixtures, it’s important to remember the primary use of the field being reseeded. For intensively grazed paddocks, typically located on the grazing platform, varieties with high scores for the grazing utilisation and quality sub-indices should be included in the mixture.

Choosing high grazing utilisation varieties will ease grazing management on farms where paddocks are readily grazed to target residuals, reducing the need for topping.

High-quality varieties are more digestible in the mid-season increasing animal production from pasture.

For fields destined for multicut silage production, located on farm out-blocks, varieties excelling in the silage trait and DM production traits can be selected.

These varieties have been evaluated within silage production systems and are proven to produce the highest silage yields. For general-purpose paddocks that will be grazed and cut throughout the year, mixtures containing high total PPI varieties will create the best seed mix.

Evaluation study

Results from Teagasc’s on-farm variety evaluation study have shown strong agreement with the PPI, with high PPI varieties performing similarly on-farm.

The on-farm study demonstrates little decline in DM production in swards up to 10 years old, highlighting the DM production persistency of perennial ryegrass varieties when managed appropriately under Irish conditions.

When discussing the merits of tetraploids and diploid varieties, the highest-preforming varieties in the on-farm study are tetraploid varieties.

They have persistent tillers that are productive and cows find tetraploids easier to graze into the lower horizons, which is really a plus from a grazed out perspective. That is why the grazing utilisation stars have been successful.

White clover will contribute to both the herbage and animal production potential of the sward

Diploid swards have more tillers, are more dense, less productive and, in many cases, are harder to graze out. The grazing utilisation trait has focused the industry on grazing utilisation. Farmers don’t want to have to correct grass swards with topping and we now have a trait that over time will eliminate topping to a large degree, which will remove this cost from the grazing system.

When reseeding, Teagasc research shows little benefit to having more than four varieties included in a mixture.

Increased numbers of varieties tend to dilute the influence of superior varieties.

Typically, 12kg to 14kg of a chosen seed mixture should be sown per acre with 1kg to 2kg of white clover included for grazing swards. White clover will contribute to both the herbage and animal production potential of the sward and the most successful establishment method of white clover is to reseed at the same time with perennial ryegrass.

The most recent clover research at Moorepark showed cows grazing grass clover swards having +40kg higher milk solids compared to cows grazing grass-only swards.