Guide to feed planning and forage for finishing lambs

Too many sheep farms fail to produce a plan for finishing lambs, missing opportunities to maximise returns for the current crop and jeopardising ewe condition ahead of the next, says sheep consultant Lesley Stubbings.

Flocks should be aiming to achieve growth rates of 250g-300g/day to get March-born lowland lambs weaned on schedule and put them on target to sell the year’s crop before September.

Ms Stubbings says this is possible through a planned approach to finishing, including:

• Setting a target growth rate to have lambs finished before the autumn
• Assessing and calculating available dry matter needed to hit targets
• Creep feeding
• Weaning at 12 weeks
• Dividing lambs into groups according to weight to tailor feed
• Supplementing grazing with forage crops or concentrate
• Weighing frequently and selling as soon as lambs hit target weights

See also: How one sheep farm benefits at sales from ‘gold-plus’ standard

Target growth rates

A March-born, lowland twin lamb needs to achieve an average growth rate of about 250-300g/day to finish by 31 August. It is quite a conservative rate and should be achievable.

When you consider how many lambs are still on farm at the end of August it shows how slow most flocks are.

Creep feeding and early growth

The younger the lamb, the less feed it requires to produce a kilogramme of liveweight. For example, a mid-March-born lamb on a high-quality diet that reaches 40kg in June will have consumed half the energy used to finish the same lamb at the same weight by December.

Weighing regularly from eight weeks will reveal how close lambs are to the eight-week target of 20kg and 12-week, 30kg target. To hit these, the young lamb must always have access to good-quality food so creep feeding should be introduced when grass or forage is limited.

If growth is lower than 200g/day this should trigger weaning and an improved plane of nutrition through better quality forage.

Dry matter availability and requirements

Hitting ewe condition of 3-3.5 by tupping time remains the priority above lamb growth. To gain condition the ewe will need more than 3% of her bodyweight in DM or between 1-2kg of DM/day.

The lamb’s DM intake requirement is roughly 4% of its bodyweight for example, 1.2kg DM/day for a 30kg lamb.

Alternatively dry matter in pre-grazing paddocks can be estimated by measuring the sward height and using the following method recommended by Ireland’s Teagasc research institute:

• Step one Subtract the desired post-grazing sward height (for example, 4cm) from the grass height that has been measured.
• Step two Multiply the figure left by 300 – because there is roughly 250-300kg DM/cm of grass.

Weaning

Most lowland sheep farms in the UK wean lambs at 16 weeks and beyond. This is too late and based on a misconception that lambs grow better on the ewe. The older the lamb, the less efficient its feed conversion and it also draws on the ewe’s resources and competes with her for grass.

The target weaning age should be 12 weeks. At this stage the lambs should be weighed and divided into weight range groups so grazing or forage can be tailored to meet the target finishing date.

Normally, it is sufficient to have two feeding groups but this year with wider extremes it may make sense to have three divisions.

Forage crops for finishing

Where grass yields are low during midsummer, forage crops can provide useful additional protein to help maintain growth rates.

AHDB Beef & Lamb has set out some of the advantages of a range of finishing crops available for lambs.

Red clover

Red clover can persist in swards for up to five years and has a taproot that helps it grow in drier conditions.

Its ability to fix nitrogen from the air and convert it to nitrates via the action of root-borne bacteria contributes to soil fertility and companion plant growth. Red clover fixes about 150-250kg N/ha making it a useful break crop.

It is capable of producing high yields of about 10-15t DM/ha/year and grows well in a mixed sward with Italian ryegrass or as a monoculture. The feed value is particularly high with crude protein at 14-19% (ensiled). Grazing trials at the University of Aberystwyth recorded lamb growth rates of 229g/day on clover swards compared with 182g/day on ryegrass alone.

White clover

White clover also fixes nitrogen although at a lower rate than red varieties of 100-150kg N/ha. White clover has a higher digestibility, protein and mineral content than grass-only swards due to the continual regeneration of leaves throughout the season and low stem development. Dry matter intakes are up to 30% higher than grass alone increasing liveweight gains at grazing.

Lucerne

Deep rooting lucerne can reach soil moisture in dry conditions when grass struggles to grow. Trials in New Zealand found lucerne yielded a four- to five-fold benefit in lamb growth per hectare (300-400kg lamb weaned a ha compared to 80-135kg lamb a ha) over grass swards alone when conditions were dry.

Target dry matter production is 12t DM/ha/year  but the plant fares worse on heavy soils prone to waterlogging.

As with the other legumes, lucerne fixes high levels of nitrogen at up to 250kg N/ha/year and has a high crude protein content of 18-22%.

Chicory

Chicory can persist for up to five years with forage yields of 6-9t DM/ha common under grazing conditions in the early years after sowing with 15t DM/ha recorded in trials in New Zealand.

Chicory is well suited to finishing lambs or carrying ewes and lambs during lactation having far higher mineral counts than ryegrass swards alone. It has also shown a useful trait in reducing faecal egg counts in lambs.

However a shorter growth season means careful management through rotational or strip grazing is necessary.

Plantain

The AHDB suggests that while plantain does not produce lamb growth rates seen with other forage legumes it can yield rates of 200–350g/day, outstripping grass pasture alone, particularly later in the summer on dry soils.

The major advantage of plantain is seen in kilogramme of lamb/ha because the tough, deep-rooted plant can sustain higher stocking densities than grass-based swards. Annual yields can amount to 17t DM/ha (6.8t DM/acre)