September is an important month if considering all-grass wintering (AGW) as pasture covers will start reducing from late September. This means the amount of grass available on farm now will determine the plan in the autumn and winter.
Research by AHDB Beef & Lamb has shown that an AGW system can offer potential savings of £15 per ewe per winter. AGW is based on intensive rotational grazing, where sheep are managed at high stocking rates and moved frequently through temporary fenced paddocks. The period for which the system can be used depends greatly on the geographical location of the farm, as winter grass growth varies significantly throughout England.
A fundamental aspect of the AGW system is grass measuring and the subsequent allocation of a paddock to a group of livestock. This can be plotted as a ‘grass wedge’ – when fields are represented on a graph in order of the amount of pasture cover that is in them (see the BRP manual Developing Grazing Strategies for Better Returns).
Nitrogen (N) fertiliser is a very useful management tool for manipulating seasonal pasture growth rate. Tactical but small N applications before the 15 September can help to build a sufficient wedge to sustain the grazing animals over the autumn and winter period. Although N responses are largest and most reliable in spring, trials have shown a significant increase in sward production levels as a result of autumn N applications. However, in fields that have been well fertilised through the year, the response will be low.
Fields that will be grazed by ewes at the beginning of winter should be shut up from September. This means lambs may need to be sold earlier than usual in the first year to achieve this. Closing should be staggered to ensure fields are at different stages of growth and the feed quality of the grass on offer to the ewes each day is consistent throughout the winter. The lambing paddocks should be allocated in the middle of the rotation to make sure they have recovered before they are needed.
Those hoping to introduce an AGW system must start building a wedge of grass up from the autumn. This will then be fed back to the ewes through the winter using a rotational grazing system. The theory is that the saved wedge, plus regrowth, should provide enough grass for ewes to be wintered on and ensure the lambing paddocks are in prime condition the following spring to avoid the need for supplementary concentrates.
Under set stocking, sheep may only utilise 50 to 60% of the grass due to rejected and trampled material. AGW systems have shown a 30% increase in grass utilisation, resulting in reduced supplementary feeding. Improved grass utilisation also aids the development of a good-quality pasture in spring, as it allows the more vigorous, improved species to excel as competition from poorer grasses is reduced.
As a general rule of thumb, covers across the grazing platform should be approximately 2,000 to 2,500kg dry matter (DM)/ha during the preceding autumn. The target for pasture cover for lambing is 1500 to 2000kg DM/ha. Therefore it is crucial that producers accurately measure grass covers continually during the grazing period. This allows graziers to forecast whether any supplementary feeding is required. A rising plate meter or compressed sward stick can be used to measure grass covers.
Sward sticks along with a ‘How to’ video are available at beefandlamb.ahdb.org.uk/grazing-club. There is a BRP+ document titled All-Grass Wintering of Sheep, which can be found at beefandlamb.ahdb.org.uk/returns