Farm Ireland

Tuesday 20 March 2018

Settled views on grassland management are changing

John Donworth

If you attended any of the Teagasc open days either in Ballydague or Ballyhaise, you would have been shown a board which stated that as you increased grass utilisation on your farm, your farm profit increased. The relationship between grass utilisation and farm profit is very strong and almost all the data shows that for each extra tonne of grass utilised, farm profit increased by at least €100/ha.

National Farm survey data for 2007 showed that we are utilising approximately 7.1t of grass dry matter per hectare on our dairy farms. Profit Monitor clients, on average, are using 7.8t of grass dry matter per hectare. Profit Monitor data also shows that the top 10pc of dairy farmers are utilising 9.4t of grass dry matter per hectare. I am assuming that the utilisation of the grass grown is 90pc.

What is being achieved at research sites? In Ballyhaise in 2008, this farm produced 15t of grass dry matter and in 2009 it produced 14.7t. For the years 2001 to 2005, Curtin's Farm in Moorepark produced 12.5t of grass dry matter. However, for 2007, they grew 14.7t and in 2008 this figure increased again to 15.7t. This is an improvement of 25pc on the 2001 to 2005 figures. So, has new technology allowed us to increase stocking rates?

Before answering the question, we should first look at the chief components of the cows' diet over a 12-month period. The 2001 to 2005 trial on Curtin's Farm established a grass intake of 4,040kg and a silage intake of 1,133kg of silage dry matter.

So, the total forage dry matter intake is 5,173kg. If the farm is growing 12.5t of grass (12,500kg) then the farm is capable of supporting 2.4lu/ha (1 cow/ac). This system is sustainable over time. The cows produced 500kg of milk solids each or 1,250kg/ha, and they received 400kg of concentrates.

What has happened in the last two years at Curtin's regarding stocking rate? Well, in 2008, the cows were stocked at 2.82lu/ha and the farm grew 15.7t of grass dry matter. Assuming that one utilises 90pc of what is grown, then the amount of grass grown just falls short of sustaining 2.82lu/ha. The actual figure is 2.73. But the cows only received 173kg of concentrates in that year and produced 430kg of milk solids per cow, or 1,220kg/ha.

However, long-held views by research personnel on grassland management techniques were changing. Chiefly, they revolved around asking cows to graze much lower than the old post grazing height figure of 6cm. Cows in the 2008 trial grazed down to a post-grazing height of 4cm. They were also going into lower covers -- 1,400kg of grass dry matter.

But, the important point of the 2008 trial was that the farm was producing 100pc of its silage requirement from within the milking block. What happened with this trial in 2009?

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Well, stocking rate was increased still further to 3.2lu/ha and, to put it mildly, the wheels came off the lorry. Firstly, it was an atrocious year, both from a grass growth and weather point of view. In spite of this, the farm grew 14.3t of dry matter, but silage stocks were well back.

A total of just under 3t of fresh silage per cow was harvested. This was about 60pc of the total requirement. Clearly, if you are stocked overall at 3.28lu/ha, providing enough winter feed is going to be a big challenge.

Several of you got by in 2009, by having an additional two blocks of silage left over from previous years. This is not the situation today. There is absolutely no silage stocks left over, even at stocking rates of 2.47lu/ha.

The current driver at research and farm level is to increase the number of cows on the milking block. As overall stocking rate increases beyond 2.5lu/ha (1 cow/ac), production per cow will suffer, but production per hectare should increase. Production per cow will be reduced by 7.4pc, while production per hectare will increase by 18pc.

So, where should overall stocking rates be pitched? Firstly, let me say that unless all the farm (both milking block and outside land) is working to the maximum (a minimum of 12.5t of grass grown), then a safer overall stocking rate is 2.25lu/ha. This might seem on the low side, but believe me, unproductive old swards are incapable of providing enough silage.

If you have everything in place and the farm is growing close to 14t/ha, then an overall stocking rate of 2.8lu is sustainable. Once you move to 3lu/ha, providing enough winter feed will always be a serious challenge. Some thinking outside the box will be required to source cheap alternatives.

Date for your Diary: Thursday (11am to 1pm) -- grass roots farm walk on the farm of Mark Newenham, Coolmore, Carrigaline, Co Cork.

Irish Independent