19 August 1997

Big silage cuts not giving chance for late autumn cover

DAIRY producers who have taken large second and third cuts of silage are destroying the chance of late autumn and early spring grazing, and creating the need for more silage.

That was the message of New Zealand dairy consultant Leonie Foster. "At the most important time to have good grass cover on the farm, especially for autumn calvers, producers are cutting it instead and turning it into a lower quality feed," said Ms Foster.

She believed one of the biggest misconceptions is that farmers who graze cows year-round do so because their farm grows grass in winter.

"The grass cows are grazing in early spring is autumn saved pasture, not winter grown grass."

Anyone keen to extend the grazing season – and every extra day was worth £1 a cow – must first ensure good access to paddocks and provide water troughs in every paddock. Then decide when you want to start grazing next spring and work out the date 120 days back. When target turnout date is Feb 10, that means closing the first paddock on Oct 10; to have grass 12-15cm (4.5-6in) long in February it must be grown in October and November, she said.

Select the driest, best accessed paddocks and graze them down to 1500kg/ha DM before applying 25-38kg/ha (25-30 units/acre) nitrogen and closing them for the winter.

Clearly, when there is little grass on the farm and you are running a 20-day grazing rotation when paddocks are being closed, the herd would be inside by Oct 30 – defeating the purpose, said Ms Foster.

"The only way to have spring grass and stay out until, say, mid-December is to lengthen the grazing rotation so it takes 60 days to get around the farm. "Have all stock going no faster than 1/60th of the farm from October. On a 45ha (112-acre) farm my 100 cows would have to make do with only 0.75ha (1.8 acres) every 24 hours. That is a lot of grass on each paddock."

It is, therefore, critical to build up the grass before then, she said. "When covers drop too low, growth is compromised which will be a costly mistake," said Irish pioneer of New Zealand grazing techniques Michael Murphy. He advised building cover gradually from Sept 1 or earlier for a spring calving herd. Average cover across the farm on Oct 10 should be about 2800kg DM/ha for spring calvers. That includes some paddocks which have just been grazed down to 1500kg/ha and others with much more grass at about 4100kg/ha which the cows will be going into.

Slightly lower average covers, at 2500kg DM/ha, are needed for autumn calvers.

When cover is too high for autumn calvers, and paddocks must be grazed to 1500kg before closing, performance could drop, he said. "Grazing too high covers with autumn calvers is bad for the grass and cows." He also advised against feeding silage at grass. "This is highly inefficient and wasteful. Only do so in a drought situation or to allow grass cover to build up quickly."

As for sheep, these were white lice that had no place on a well run dairy farm he saidn

Good access to farm paddocks is vital to maximise use of grazing.