10 July 1998

Should UKfollow NZs lead?Yes, but with care

Management of grass for

sheep – where New

Zealand leads, do we follow?

SAC sheep specialist

John Vipond, who travelled

there on a Stapledon

Fellowship, reports

THE UK dairy industry is currently grappling with New Zealand ideas of grazing management in an attempt to reduce production costs and restore margins cut by falling milk prices. Should the sheep industry follow this lead? Specifically, should it be describing grass by kg dry matter/ha (DM/ha) or continue using sward height and should UK producers be rotationally grazing sheep?

Most New Zealand farmers still describe pastures for sheep by sward height but the top operators use DM/ha. Pasture DM/ha measurement can be achieved by getting-your-eye-in, which involves measuring sward height with a ruler or sward stick and doing a series of pasture sample cuts, drying the grass in a microwave oven. This is too much bother for most farmers – who may use a ready-made device, such as a grassmeter or falling plate meter. The grassmeter essentially measures the water content of pastures and accuracy is affected by rain and dew. The falling plate meter, to be accurate, needs regular calibration.

Most farmers rely on sward height for day-to-day decisions, such as when to move stock, but for tactical decisions, for example when should a group of animals be sold, estimating sward dry matter has an advantage.

Rotational grazing

Choice of grazing system has less effect on efficiency than overall stocking policy decisions such as the number and type of sheep to keep, calving and lambing dates and conservation policy. Getting these right is a first priority. After lambing and in early summer, there is little justification for rotational grazing but as the season progresses to after weaning there can be advantages of a leader follower system.

The main use of rotational grazing is to allocate winter feed – standing pasture – so that it is used economically. If the UK is going to get mild dry winters, this approach is technically feasible on strong soils that are well-drained and can handle heavy stocking pressure. The winter grass acreage is divided using temporary electric fences into 100 paddocks with daily shifts. Supplementary forage is fed at the beginning of the winter to build up pasture cover in spring. Where this system works, the need for supplementary winter feed such as hay or swedes is minimised.

So does the UK industry follow the New Zealand lead? Yes, but with reservations. There are too many differences between the two countries to make direct transplants of systems – some components of their systems may work here, often after modification. The UK must allow for its harsher climate and the public concern intensive stocking creates.

UK producers do not need to move away from describing pastures by sward height. All grass wintering involving rotational grazing could reduce wintering costs but would need careful thought and planning and would require an escape area – hard feeding stand – as a back-up in long wet spells which otherwise could compromise welfare.

Weed suppression

New Zealand farmers have imported sheep breeds with high lean growth rate – Texel – and milk production – East Friesian – and are now recognising pasture quality as their major constraint, not pasture amount. Emphasis is now on controlling seedheads and weeds and improving clover content to raise quality.

Many farmers are experimenting with the suppression of seedheads and weeds in pastures using Round-up. The spray is applied at 250-500ml/ha when the ryegrass is at the early heading stage and growing rapidly. At this stage the ryegrass is less affected by the herbicide which is harder on weed species. Animals do not need to be kept off pastures although are often taken out for two to three days. They find the yellowed grass more palatable and the treatment tends to improve ryegrass and clover content. Thistles are checked but not killed.

It is hoped that by increasing the percentage of preferred species pasture renewal costs can be deferred or possibly eliminated.

Half the eight farms visited carrying out seedhead and weed suppression treatments showed visible improvement in pasture – that is more clover and less seedheads. It was too early to tell if pasture composition had been affected. In a good growing season where there is an excess of feed in May it could help control grass, keeping it in a vegetative leafy state. Hard grazing by lactating ewes in May can have the same effect but, unless the ewes are in good condition, this can check milk yield and lamb growth.

But the glyphosate approach is probably not suitable for improved grassland in Britain. There is no information yet on cost benefits. With the UK climate, the check to grass growth is greater, and may be unacceptable. Work at SAC showed that in a ryegrass/clover sward, grass growth was severely checked by very low doses of glyphosate, allowing clover to dominate.

It is possible that the technique may be more useful on some hill pastures, but further work would be needed to test this in our climate. Environmental concerns have also to be taken into account in treating extensive hill ground in this way.

&#8226 A useful source for information on building up pasture cover over winter is a recent New Zealand Sheep Council Publication A Guide to Feed Planning for Sheep Farmers ISBN 0-908768-25-7.

TAKE HOME MESSAGES

&#8226 UK industry should describe pasture using sward height.

&#8226 Rotational grazing has benefits for all grass wintering.

&#8226 Allow for harsher UK climate and welfare concerns.