Maize grain harvested and crimped on a Pembrokeshire farm this week could help a dairy farming business achieve a target milk yield increase of 1,000 litres per cow.

Michael and Gwyn Roblin, who farm 530 acres at Clynderwen and Glynty Farms, Llanfallteg, were the first farmers for more than a decade to grow maize as a grain crop in Pembrokeshire. The crop yielded nearly 5.5 tonnes an acre.

They drilled 21 acres of seed and have calculated that the crop cost them just over £180 an acre to grow. The brothers admit it wasn't the cheapest crop, but are confident there will be a payback from the high starch content of 65%.

Nearly half this starch by-passes the rumen and has the potential to increase milk and milk protein yields.

The herd of 200 milking cows at Clynderwen and Glynty Farms is averaging 7,200 litres at 4.1% butterfat and 3.44% protein.

The aim is to eventually increase that average yield by 1,000 litres. "This crop will provide a high energy feed for the herd,'' said Gwyn Roblin.

"It has been an experiment this year, but if the costs are comparable with bought-in concentrates we will consider growing it again.''

The crop was harvested with a Cressoni header supplied by Kelvin Cave Ltd, fitted to the Roblins' own combine harvester.

The maize was grown under plastic, a cost of £55 an acre, to achieve the required stage of maturity in October. Ideally, the crop should have been harvested a week later but with rain forecast Michael and Gwyn were advised to get the crop off the field. However, the crop grown under plastic could feasibly have been drilled at least three weeks earlier to bring forward the harvesting date.

Analysis showed that the grain was harvested at 65% dry matter.

The grain was crimped and ensiled and will be fed to the herd through a total mixed ration system.

Lyn Davies, of Meurig Davies Farm Seeds, Llanboidy, supplied the maize seed. The experiment, he said, was intended to determine how this crop, grown in west Wales, compared with wheat in terms of starch and dry matter.

Trials of forage maize grown under plastic had achieved significantly higher levels of starch than crops cultivated under conventional conditions, he said.

"Even in a good maize growing area there is an argument for using plastic,'' he said.

"Early varieties perform particularly well. Trials conducted in Ireland over the last six years demonstrate that maize drilled at the beginning of April and harvested at the end of August performed well under plastic and enable farmer to use varieties which would not normally be grown in the area.''

Andy Strzelecki, technical director for Kelvin Cave Ltd, stressed that maize grain was not a replacement for maize silage.

"Farmers need to address their forage needs first,'' he said. "This crop does not compete with maize silage but with concentrate feed imported onto the farm.''

The Roblins also grow 56 acres of forage maize under plastic and 520 acres of grass silage to feed to 350 dairy cows and heifers and 200 beef cattle.

The maize, Mr Strzelecki suggested, was particularly suitable for dairy and beef finishing systems.

A typical analysis of crimped maize grain shows a dry matter of 67-70%, crude protein of 9.5-10.5% and an ME of 14 - 14.5%.