24 October 1997

Dairy-style grazing gets lambs to fulfil potential

Rotational management of

grass/clover swards and

extended grazing helps

maximise lamb performance

on one Irish unit. Sue Rider

reports from the Irish

Grassland Associations

sheep conference

TOP quality grass management is the key to high output for one Irish sheep unit producing mid-season prime lamb for export.

The 200-ewe March lambing mainly Belclare x Cheviot flock at Knockbeg, Carlow, is stocked at 14.6/ha (six/acre) and achieves 400kg/ha carcass output, gross margins of almost £64 a ewe and £893/ha (£361/acre), and 1.7 lambs reared a ewe compared with the national average of less than 1.3.

Researcher at the unit run by Irish advisory service Teagasc, is Sean Flanagan. He attributes this performance to management of the grass/clover swards. "Grazing management on the farm is very important for sheep production efficiency," he told delegates at the Irish Grassland Associations Sheep Conference, Co Carlow.

"Sheep producers should take on board some of the management techniques used by dairy farmers to get more from grass and save on feed and labour costs." At Knockbeg, paddock grazing, regular measurements of grass using a plate meter or sward stick, and extended grazing were practiced to lift profits.

Lambing in mid-March matches grass growth with thefeed demands of the flock without the need for concentrates post-lambing, he said. Extended grazing this winter will cut feed costs further, and the labourassociated with indoor feeding.

Ewes are housed on Feb 1. The priority is to have adequate supplies of grass to meet high feed demands of ewes after lambing.

Some paddocks on the main grazing area are dressed with 34kg/ha nitrogen on about Feb 1

As well as using fertiliser N for early grass – due to the late clover growth – 100kg/ha (80 units/acre) N is applied for silage and 34kg/ha (27 units/acre) for aftermaths and autumn grass.

To maintain high clover contents for weaned lambs – about 30% – no N is used on the main grazing area in the summer.

"The clover fixes 130-140kg N which is available for grass growth, this saves us 8-9p/kg deadweight."

After turnout, all paddocks are grazed for two to three weeks with about 30 ewes plus lambs a paddock to avoid mis-mothering. In early April, one 3 ha (7.4-acre) paddock is closed for silage; stocking rate is 16 ewes a hectare (6.5/acre).

Ewes and lambs are then grazed rotationally until weaning in mid-June.

"Paddock grazing gives us better flexibility to manage the grass. We can assess the paddocks regularly. Sward surface height gives a good idea of grass supply and by measuring it on a regular basis, grass surpluses/deficits can be foreseen and corrective action taken." Speed of the grazing rotation is based on sward surface height assessments in the paddocks.

Spring grass is grazed down to 3-4cm (1-1.6in) sward surface height in April. But in May to June post-grazing sward surface height is higher at 5-6cm (2-2.4in).

"Grazing more tightly forces lambs to graze the less digestible base of the sward, which reduces weaning weight," said Mr Flanagan. But leaving any more grass would allow seed heads to develop. "When grass becomes stemmy digestibility is lower and lamb intake and growth rate fall."

To avoid this any surplus grass is closed off and cut for silage in late May and in August.

"To maximise lamb growth rate we aim for a post-grazing sward height of 8-9cm combined with a high clover content. We also keep the aftermath from the August silage cut for grazing lambs in September and our paddock system allows leader/follower grazing, with ewes grazing behind the lambs."

Lamb growth averaged 200g a day in July/August and 160g a day in September, said Mr Flanagan.

"We drafted lambs for slaughter at liveweights of 38-44kg, and after handling for degree of finish."

About 15% of lambs are still grazing and will be sold in November.

Pasture for flushing, before the tups start work in October, is built up from early September as lambs are drafted off and paddocks released for resting.

Banks of grass are built up for grazing in November/December, keeping a close watch for deterioration at the base of the sward.

Ewes will be housed on Feb 1 for five weeks before lambing. "Extending the grazing season allows us to reduce feed costs."

Making better use of grass in this way – while maintaining performance a ewe – would help achieve their target of 500kg lamb carcass a hectare, he said.

Paddock grazing of ewes allows grass to be measured regularly, so that any surpluses/deficits can be foreseen and corrective action taken.

Sean Flanagan: "Sheep producers should take on board some of the techniques used by dairy farmers to get more from grazed grass."

Lamb performance 97

No ewes/forage ha14

No lambs reared/ewe mated1.62

No lambs reared/forage ha22

Lambs finished off grass85%

Carcass weight (kg)18

Carcass output/forage ha (kg)408