2 February 1996

Facing a fresh challenge

Ideas on maximising use of grazed grass and the role of maize within that system were to the fore in Devon last week. John Burns reports

MAKING grass available in late autumn and early spring is the easiest part of grazing management Dr Sinclair Mayne of the Hillsborough Research Institute, NI told the Joint BGS/MGA conference Forage Maize in Extended Grazing Systems at Exeter, Devon.

That was certainly the case in recent years, with grass growing 11 months of the year. The bigger challenge was using it, he said.

But Co Cork farmer Paddy OKeeffe, who runs a 200-cow autumn calving herd, disagreed. He said the most difficult part was growing enough grass out-of-season, especially on heavily stocked farms.

"The amount of grass you can build up for late season grazing is completely dependent on stocking rate. This is a fact of life which has to be faced."

From late-July to early-October grass growth rate in Cork averaged 42kg dry matter a hectare a day, but could be increased by extra nitrogen and longer rests between grazings. At 2.25 cows/ha (0.9/acre), only 35kg/ha (14kg/acre) would be removed each day and so reserves could be built up for later use. But at his own average stocking rate of 2.7 cows/ha (1/acre) there would be no surplus of grass.

So to ensure he had grazing in October and November, he halved his stocking rate in late July by sending dry cows to his heifer-rearing farm until they calved from mid-September.

From early July, swards were grazed less tightly (leaving 8cm) than in the early season (6cm), and longer rest periods were allowed.

Some 55kg N/ha (44 units/acre) was applied in late July, again in August and another 40kg/ha (32 units/acre) in September.

The amount of grazing available was measured regularly and rationed carefully. A typical daily ration for fresh calvers from late September until November 25 would be 10kg DM as grazed grass, 5kg DM as maize silage, and 5kg concentrates.

This year there was so much grass that grazing continued into December in wetter conditions. Attempts to increase daily grass intake by reducing maize silage and concentrates, failed because milk yield of cows giving over 30kg fell.

So the season ended with grass being cut and carted to the cows. That system worked well and Mr OKeeffe was considering using it again for late season grass.

Ensuring early spring grazing was even more important. "One kg of grass dry matter in March is better feed than one kg in November. The cow prefers it and performs better on it." But there was also evidence that paddocks grazed in late November produced less grass the following March. Research at Johnstown Castle had shown that one kg dry matter removed in November meant 2kg less available in March.

Mr OKeeffe called for more research into ways of increasing grass production out of season. In particular, it was a great challenge for plant breeders. His own experience with early perennial ryegrasses was mixed. They did produce more early grass but proved difficult to manage well in mid-season.

Dr Sinclair Mayne: "The next challenge is using grazed grass."