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Assessing supply and demand for the autumn rotation

As we move into the latter part of August it’s important we start to plan and implement an autumn grazing plan on farms. Ciaran Lynch, Teagasc Sheep Specialist, discusses grassland management, assessing the flock's grass demand, and building grass supply.

As some of the management priorities shift such as setting up the closing plan for the  farm and building a reserve of grass ahead of the flocks we still need to focus on achieving high levels of lamb performance and  build condition on ewes prior to the mating period.

Grassland Management

Maintaining sward quality has been challenging on many farms during late July and early August not helped by the Soil moisture deficit experienced by many at the start of the month. Most farms by now should be operating a leader follower system allowing the lamb’s access to the best quality grass.  For lambs aim to turn them on to paddocks with pre grazing covers of 1200-1500kg DM/ha or 7-9cm, this will increase slightly in September (see targets in Table 1).  These swards should be grazed down to around 6cm with lambs. Ewes should follow in the rotation when to graze these swards out to between 4 and 4.5cm.

Thinner ewes should be managed separately from the main bunch and instead grazed alongside replacement or finishing ewe lambs on higher quality grass to give them a better opportunity to improve body condition.  As the month progresses it’s important to start grazing paddocks in the rotation you intend to close them in October and November. Aim to clean these fields out properly in the coming rotation, this will leave it easier to graze these fields out in the final rotations and will improve the quality of grass carried over winter and into early spring. Remedial action in the form of topping may be needed to remove dead material on some paddocks as ewes fail to graze them out fully.

Assess Demand

Take stock of what the flocks grass demand is for the autumn and how long they will be kept at grass during the winter as this will have a significant influence on managing supply. Aside from the number of ewes and replacements on the farm from September onward we also need to factor in their requirement – i.e. thinner ewes will need access to better grass supplies. We also need to weigh up how many lambs remain on the farm for finishing and equally as important how close they are to finish. The latter is often a pitfall many farms fall into in early to mid-September with a lot of light lambs remaining on farm.

Although some farms have scope to carry lambs later into the season, this needs to be planned out in advance. However many farms will need to consider introducing concentrate supplementation to boost lamb performance and reduce finish times. Target this supplementation where needed at those closer to finish first, providing up to 0.5kg/hd/day will offer good levels of response.  Another option worth considering for farms that may not be able to match supply is selling a proportion of lambs as stores thereby reducing demand. Assess the potential demand in time and put a plan in place to meet it.

Building Supply

To compensate for reducing grass growth Farms need to be building towards 25 to 30 days grass ahead by September (see Table 1).  It will be important over the coming weeks to ensure paddocks receive some level of Nitrogen application to allow grass to continue to grow into the autumn. Response rates will decline as we approach the September fertilizer deadline so aim to spread earlier, ideally before the end of August weather permitting to take advantage of better growth rates and fertilizer utilisation.

Higher stocked farms (>10 ewes/ha) should be applying up to 30 kg N/ha (approx. 25 units/ac) in the form of protected urea while lower stocked farms (<10 ewes/ha) can reduce this slightly applying up to 20 kg N/ha (approx. 15 units/ac). Where soil fertility issues need to be addressed or where surplus was removed for silage target these with a suitable compound fertiliser to replenish P & K offtake. Spreading remaining slurry or FYM on these areas is another option to replace offtakes and build soil fertility - just ensure good graze outs prior to slurry or FYM application.

Table 1: Suggested Sheep grazing targets for autumn/early winter

 Pre-grazing yield
(kg DM/ha)
Target days aheadRotation length
August 1250-1500
15-20 days 25-30 days
September 1500-2000
25-30 days 25-30 days
30-40 days Closing paddocks from mid-October

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The Teagasc Sheep Specialists issue an article on a topic of interest to sheep farmers every second Tuesday here on Teagasc Daily.  Find more on Teagasc Sheep here