KEEP AN EYE ON GROWTH OF GRASS
Assessing grass regularly is the only way to estimate how much is being used. Jonathan Riley reports
OBSERVATION and flexibility are two of the key factors in successful grazing management for dairy cows, reckons New Zealand adviser Mark Blackwell.
He says it is vital for producers to get an idea of how fast the grass is growing and then match this growth to the cows daily intake.
"Regular assessment of grass levels is the only way to estimate how much grass is being used. This will then give two weeks prior warning of insufficient grass levels and action can be taken. Wait until the milk yields fall and it is too late," Mr Blackwell told a Notts Grassland Society farm walk at Kingston Farms Kneesall Estate, Notts.
He claimed producers using rotational grazing had a distinct advantage over continuous or set-stocked regimes because they could see the next field to graze. "These producers have the advantage of being able to see their next feed stock in front of them," he said.
"Those that do assess grass levels in the UK use sward heights but it is preferable to think in terms of cows eating kg of grass just as they eat kg of silage or any other feed.
"On average a cow consumes 15kg of grass dry matter a day, so producers should assess consumption a hectare, estimate grass yields and then assess whether a chosen stocking rate is sustainable."
Quantity in kg/ha could be converted from sward heights (see table) until it was possible to assess kg/ha by eye, he said.
Tony Tapper, farm manager at Kingston Farms Kneesall Estate, said grass was a scarce commodity in the eastern regions, with annual rainfall at only about 580mm (23in). "This year we were prevented from turning cows out because there was insufficient grass after successive frosts," he said.
He aims to make 10t of silage a cow and use some as a buffer in August. To achieve this he stocks his 258 cows at 8/ha (3.5/acre).
"This year this stocking rate has put severe pressure on the grazed area," said Mr Tapper.
Mr Blackwell suggested the silage area could be opened up and small blocks grazed or strips mown and the cut grass fed to grazing cows. "But in the longer term a revised policy at turn-out could be adopted with cows turned out for a few hours a day to better match the grass growth with intakes.
"With a herd of this size turn-out could be organised in groups gradually building up to full turn-out over a period that better suits the grass growth," he said.
New Zealand adviser Mark Blackwell (right) shows farm manager Tony Tapper how to assess grass yields in kg DM/ha using a rising plate meter.