Ivan Susan and David Thomas are farming in Derrycooley just outside Tullamore, Co, Offaly. The Thomases converted to dairy in 2018, coming from a tillage and suckler-to-beef background. David studied animal and crop production in UCD and graduated in the summer of 2017. As part of David’s work placement, he spent some time working on dairy farms and when he finished college, the family explored the option of converting to dairy.

In making this decision, they kept an open mind as to what system they would go with and in the end, decided to go with the Lely robotic milking system. One of the main reasons for this was the existing sheds could be converted with minimal cost. Another reason was the flexibility robotic milking brings, as Ivan and David do most of their own machinery work.

In the spring of 2017, they purchased 30 maiden heifers and a further 70 in-calf heifers that autumn.

The herd is predominantly a high-EBI black-and-white Holstein Friesian base with a small number of crossbreds. The heifers were sourced locally with the help of their farm adviser.

The Thomases started milking 100 heifers through two robots in spring 2018 on an A, B, C grazing system. In this system, cows change paddock every eight hours, which encourages them to head back to the yard to be milked. Since then, they have added a third robot. The herd has grown each year since starting and this year they are milking 207 cows.

Infrastructure around the farm was a priority, as the cows were moving every eight hours. Roadways were added and existing ones improved, with multiple access points added to paddocks in order to increase days at grass in the shoulders of the year.

An underpass was also built to give better access to another part of the farm. In the yard, slurry storage was increased along with feed space in the existing sheds and a new cubicle house was added to cater for the growing herd.


From the start of the conversion, grass was one of the main focuses. While running a beef and tillage enterprise, Ivan had a reseeding programme in place as part of a crop rotation. In the run-up to the conversion, the area of the farm in tillage was greatly reduced. In 2018, David began grass measuring, which he said helped with the management of the grass, from grazing the right covers to knowing when to take out surpluses.

Starting from a blank canvas and having a robotic milking system made the Thomases both unique and an ideal farm to participate as a DLF seeds and science farm partner. From 2018, they started to reseed using DLF monocultures as part of a trial in which DLF was assessing the performance of some of its new varieties.

David was keen to mention the success they have had with tetraploid monocultures on the dry or “moorey” soil on the farm, saying: “In the past, we would have only used heavy soil grass seed mixes from the local co-op and were afraid of the openness of tetraploid mixes on the moorey soil.”

David said his preferred option would be a three-way mix of the top-performing tetraploids over monocultures, taking advantage of the positive attributes of each variety in the mix.

When reseeding in Ireland, the most common diploid to tetraploid ratio is 60:40, respectively. Diploids are historically included in seed mixes because of their persistency and ground cover, while tetraploids are known for their openness, high growth rates and palatability.

Over the years, DLF has worked on breeding tetraploid varieties with the positive attributes of the diploid varieties. In 2021, DLF started an exciting new grazing trial on the Thomas farm and three other partner farms. The aim is to see how varieties perform on a working farm with its management, livestock and weather challenges compared to controlled plots.

The trial is being run over the next two years by DLF and is modelled on the grazing trials being carried out by Teagasc Moorepark. This year, the grazing utilisation trait was added to the pasture profit index (PPI). This is a measure of how appealing the variety is to the cattle grazing it. Other traits included in the PPI are spring, summer and autumn growth, quality, digestibility, persistence and heading dates, etc.

This new grazing utilisation trait is ranked on a star rating, five stars being excellent and one star being moderate.

Out of all the varieties trialled in Teagasc Moorepark to date, only three were given a five-star rating. These varieties were Astonenergy, Aspect and Xenon. DLF has sown 21 replicated plots consisting of 11 varieties in the very early stages of development and 10 of the most commonly sown varieties currently on the market.

The 21 varieties are sown in 3m x 7m plots on the four partner farms in Kerry, Meath, Waterford and the Thomas farm in Offaly.

“The overall aim of these trials is to see how all of the varieties, old and new, perform in a real-life grazing rotation, with all of the variables that climate, management and livestock can bring. The main metrics we are looking at are around grazing performance, so things like growth rate, graze-out and grass utilisation will be measured over two years,” said Paul Flanaghan, general manager of DLF Ireland.

While on the Thomas’s farm, we visited the paddock with the 21 plots. This paddock is grazed as part of a rotational grazing system and treated the same as any other paddock on the farm.

As part of the study, when the paddock reaches a suitable pre-grazing cover, Dr Thomas Moloney, product manager at DLF, measures each plot to get the exact pre-grazing cover of each variety. Following each grazing, Dr Moloney returns to measure again, to work out the residual of each individual variety.

Samples are taken from one of the farms for quality analysis from the second grazing until the fifth grazing.

Each variety is sampled for metabolizable energy (ME), protein, NDF and dry matter. It is hoped that by the end of this trial, DLF will be able to establish what new varieties will perform well on-farm.

By measuring the ME and grazing utilisation, the energy intake can be calculated. This will help to establish what varieties are best suited to the Irish grass-based system. While this project is in the very early stages, there have been common trends seen across all farms, but it was pointed out on the day that there is no doubt some results will change as the year progresses.

After the two years, the results will be compiled to find the best-performing varieties. These results will be published and will form a base for future breeding programmes, which DLF expects will be centred on the grazing performance of a variety.