Managing sheep-grazing forage crops

IN RECENT years there has been an increased interest in the potential in using forage crops in sheep systems.

Forage crops are available for feeding, mainly from October to March, replacing grass, which is either closed off or in short supply.

For finishing lambs post-weaning, rapid-growing crops such as Tyfon or Rape are most suitable, as these can be sown in April so that the first grazing will coincide with weaning time in around June orJuly.

These crops have the added advantage that, where they are leniently grazed, they will regrow for further grazing every five to eight weeks.

Other crops that are destined for finishing store lambs in the late autumn/winter can be sown later and will, generally, only provide a single grazing.

In general, brassicas destined for out-wintering stock should be completely grazed by early March as they tend to flower after the winter, which may lead to health issues for stock grazing flowering plants/ seeds.

Crop utilisation of around 70 per cent and higher can be expected, depending on the crop type, yield, grazing management, weather conditions and soil type.

Forage crops are most suited to lighter animals.

A runback area allows for a greater number of lambs to be finished off with any given crop.

Where ewes are grazing brassicas with young lambs, a runback area and shelter are required.

Care must be taken not to force animals too hard to consume unpalatable parts of the crop, such as roots, stem and soiled leaves.

Where crops are under-sown with grass (summer crops), a back fence to allow regrowth is essential.

Block grazing in one to two weeks seems to be the preferred option of sheep.

Sheep on forage crops need a fibre source of hay/silage making up about 30 per cent of the diet.

As a general guide, lowland store lambs can be expected to increase liveweight by between 100 to 150g per day while grazing forages in autumn.

Forage crops are generally low in trace elements such as selenium, iodine, copper and cobalt, so access to high-quality minerals or boluses are necessary to avoid any potential problems.

Brassicas crops contain goitrogenic substances, which inhibit the uptake of iodine by the thyroid gland.

When feeding crops – such as kale – to pregnant ewes, supplementation with Iodine will overcome the potential problems associated with goitre and high mortality in newborn lambs.

Check your flock for lameness, and make sure to remove lame sheep for treatment before the introduction to the forage crop.

Adapt sheep gradually to crops over at least one week and don’t graze older ewes on roots, as it may damage their teeth.

If finishing lambs on forage crops, they may need to be removed off the crop for the last few weeks before marketing takes place.

When growing a forage crop, decide from the different forage crops which best suit your farming system and what sheep will be grazing forage crops: for example, store lambs or breeding ewes.

From the expected yields, you will be able to work out intakes and carrying capacity, which will give an idea of how long the crop will last.

You must then decide how to graze the crop to get maximum utilisation.