BGS, RABDF, DairyCo Farm walk - David Lee

BGS, RABDF, DairyCo Farm walk - David Lee

Friday, April 9, 2010

When it comes to maximising use of grazed grass, David Lee says the most important factor is the amount of residual grass cows leave behind after 12 hours in a paddock.

This will ensure subsequent growth is of the best possible quality, he told 200 people attending the BGS, RABDF, Dairy Co Milking Grass for Profit farm walk, at his Shropshire 300-cow dairy unit. To achieve the right residual, means knowing the amount of grass available, the kg of other feeds going in and the amount the cows need to eat. David measures this in kg of DM/ha using a platemeter, so he treats the diet the same as if he were feeding a total mixed ration.

With the slow start to grass growth this spring, the amount of grass in paddocks as cows were going in at our visit on April 8th was only 1900kg DM/ha (about 6-7cm) and his aim was to graze to a residual of 1400kg of DM/ha (about 3cm).  "Until late March our grass growth rate measured 0kg DM/ha a day, when it should have been 30-40kg a day, so this spring has been a challenge," says David.

This means he is still feeding his spring calvers maize silage at 6kg DM a head and concentrate at 4kg DM a head. But with grass starting to grow now, maize silage would soon be reducing and the grazing rotation speeding up so cows would graze paddocks every 18-19 days. When there was enough grass DM available to meet cow needs concentrate would also be reduced.

David uses concentrate as a management tool and would feed it rather than silage in summer. His aim was for low input, but not to achieve a low output, as he needs to sell enough litres as well as keep costs down. This sees concentrate use fluctuate year to year with 500kg a cow fed in 2009 and up to 800kg in a poorer year. Yields average 5900 litres a cow but with butterfat and protein increased by Jersey crossbred, David points out this is equivalent to about 7000 litres at a standard 4% fat.

Achieving this amount from grazed grass, has been a 12 year process since switching from higher inputs, to spring calving and a focus on grazing - involving joining local grazing discussion groups.

First, cows needed to be trained to eat the grass. "Training cows to eat means shutting the gate, then leaving them there to get on with it. They will moan a bit to start with. But now they know what they are there for." The crossbred cows he has been building up numbers of over the last 10 years are even better at grazing tight than the Holsteins.

His strategy on slurry use and low supplements also helps with the issue of cows avoiding grazing close to dung pats later in the season. "In early spring when maize is still in the cow diet you can see the dung pats, but when they are just on grass the muck is looser and soon disappears. We also spread thin slurry immediately after some grazings and still come back to that in 18-21 days to graze. This means all the grass will smell the same."

But you can overgraze he warns, particularly with the crossbreds, if not enough grass or supplement is allocated. "At a grass residual of 1200kg DM/ha the grass will take a long time to grow back."

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