Irrespective of what grass varieties a farmer chooses to select, the ‘three-leaf rule’ still kicks in every time when it comes to determining when cattle can best utilise the resulting sward.
This was one of the key take-home messages delivered by DLF Seeds’ general manager, Paul Flanagan to those attending a recent open day, hosted by Co. Meath dairy farmer, Kevin Crinion.
Currently, DLF is sourcing new grass genetics from a range of countries, including the Netherlands and New Zealand, which are then critically assessed under Irish conditions.
The Crinion farm is one of the sites used by DLF to carry out the assessment of new grass varieties under actual grazing conditions.
Grazing
The plots are located within the grazing block and are grazed by mature dairy cows as part of the normal rotation followed on the farm.
Paul Flanagan commented: “The aim of the trial is to see how perennial ryegrass varieties, new and old, perform in a real-life grazing rotation with all of the challenges that management, livestock and weather bring.
“We have collected a massive amount of data from across the country during this trial and it is giving us a very clear picture of what makes a great grazing variety.
“The key traits we are looking for in a grazing variety are the potential utilised yield i.e., the amount of grass actually consumed by the animal and also the residual or post-grazing sward height,” he added.
These traits are closely linked with dry matter (DM) yield and quality, but also physiological characteristics of the variety like leaf size and density.
The testing work carried out to date strongly indicates that cows prefer to eat tetraploid perennial ryegrass varieties and farmers are now conscious of this when choosing grass mixtures.
“What our data tells us is that tetraploid varieties are better suited to grazing systems than diploid varieties,” Flanagan continued.
“This agrees with similar trials comparing tetraploid to diploid varieties and is primarily due to larger leaf size, greater digestibility and general ease of grazing with tetraploids.”
The utilisation of grass grown is a key performance indicator of any enterprise.
Each extra tonne of grass utilised is estimated by Teagasc to be worth an additional €256/ha. Maximum grass utilisation can be achieved by selecting the right varieties and mixtures.
“The grazing utilisation trait is a very positive addition to the pasture profit index because it provides farmers with information that was previously unavailable from independent data,” Flanagan said.
“For years we have been asked about grass palatability and how mixtures and varieties will graze out and while we already knew that tetraploid varieties graze better than diploids, the new trait on the Pasture Profit Index confirms this.
“The traditional grass mix is a blend of diploid and tetraploid with the diploid historically included for density and persistence while traditional tetraploid varieties tended to be very open and upright.”
The last decades of breeding have brought the positive attributes of diploid grasses into tetraploid breeding programmes.
“We refer to this type of variety as NxGen tetraploids, combining the density and persistence of diploids with the quality and graze out of tetraploids,” Flanagan added.
“Xenon was the first achievement from that work and has been my personal favourite variety for some time for that reason. It is one of only three varieties that achieved five stars on the new grazing utilisation trait.”
Nashota is the second NxGen variety that DLF has brought to the Irish market and is up at the top of Teagasc’s Pasture Profit Index (PPI) ranking. A grazing score is currently not available for it.
The open day also provided the DLF team with the opportunity to discuss the benefits of white clover inclusion in grazing swards.
The use of the legume in grass mixtures has the potential to offset up to 150kg of inorganic nitrogen (N) per hectare per year.
So with fertiliser prices increasing all the time, the incorporation of white clover into grass swards has the potential to greatly reduce the reliance on inorganic N fertiliser and increase the financial and environmental sustainability of Irish farms.