Farm Tech

In The Paddock
Seasonal sheep flock management tips June 2002

Managing mid-pregnancy shearing – Ewe survival and welfare depends on good shelter after shearing

Key points

• Mid-pregnancy shearing of crossbred ewes is becoming common as a means to increase lamb birth weight, improve lamb survival and wean heavier lambs.
• Sheep should be shorn with winter combs. Lifters or blades may be necessary in some environments.
• Shear ewes in mob sizes that can be adequately fed and sheltered.
• Get shorn ewes onto sheltered pasture well before dark.
• Covered yards and/or the woolshed should be available for emergency shelter.

Mid-pregnancy shearing of ewes is becoming increasingly common in New Zealand.

Shearing around day 70 of pregnancy can increase lamb birth weights by around 0.4 kg. This can increase survival rates of twin lambs by 3–4 per cent, and result in higher lamb weaning weights.

Mid-pregnancy shearing can also enhance ewe survival, improve wool quality and reduce seasonal overdraft interest charges. However, it requires careful planning and management to protect shorn ewes from cold stress.

Ewe heat loss

When air temperatures fall below a certain level, warm-blooded animals like sheep must increase their heat production to keep their body temperature in the normal range. Wind and rain can accelerate the rate at which heat is lost from the body.

Fleeces have insulation properties, which vary with the fleece type. The effect increases with the length of the wool.

Shearing has been shown to increase the energy requirements of sheep by 20–30 per cent in summer and autumn and 50–70 per cent in winter.

Pregnant ewes are quite different from their non-pregnant or lactating counterparts. They do not increase feed intake to compensate for increased heat loss, but undergo hormonal changes that allow them to burn up stored fat to provide extra energy.

This is the source of energy for the increased foetal growth associated with mid-pregnancy shearing. For this reason it seems that shelter is more important than better feeding straight after shearing.

Shearing method and cold stress

The shearing method has a large bearing on the length of wool left on the sheep and how much insulation it provides after shearing.

Massey University measured resistance to cold stress in sheep shorn by standard and winter combs and found that cold stress was greater in sheep shorn with standard combs.

They also compared winter combs and blade shearing in wet, windy conditions. There were no differences in cold stress in cold and windy conditions but, when it rained, cold stress was greater in sheep shorn with winter combs than those shorn with blades — a difference which lasted for 10 days after shearing.

Winter combs have nine teeth and a sled on every second tooth. They are also referred to as ‘Cover Combs’ — a popular brand of winter comb. From May onward, winter combs should be used in all regions of New Zealand.

The use of winter combs with attached ‘lifters’ is becoming more common in colder regions. Lifters comprise a plate with sleds that is screwed underneath the winter comb, raising it by a further 2.5 cm. Lifters are replacing blades in some areas.

Each of these options, including blades, has their place depending on the regional climatic risk factors.

Most of today's shearers are experienced in the use of winter combs. Although they require careful use, many shearers find well-prepared winter combs enter sticky wool more easily than conventional combs, enabling faster shearing.

In the South Island when shearing full-wool ewes with winter combs plus lifters, a full belly crutch is often done six to eight weeks beforehand. This is a sound practice — it is very difficult to remove belly wool with lifters. The extra two months' belly wool growth may also help reduce cold stress after shearing.

Weather forecasting

Getting a good weather forecast is very important, to not only have the sheep dry, but also to avoid storms that could result in significant sheep losses.

Weather forecasts in advance by five days or two months can be obtained from your local METPHONE 0900 number for $1.15 a minute. If you prefer faxed information, contact METFAX 0900 77 999. This costs $5.40 for the first minute and 99c a minute thereafter.

If the 5 day and 2 month forecasts are unsuitable you can call the Forecasting Room at a cost of $30.

More information can be obtained from Call Free 0800 932 843 or 0800 WEATHER. The METSERVICE web site is www.weather.co.nz.

Subscribers to www.fencepost.com can get a 12 day regional forecast.

Let your contractor know

If you are planning to change your shearing programme to include mid-pregnancy shearing of ewes, don't forget to let your shearing contractor know well in advance.

More information

• In the Paddock, May 2002. Shearing crossbreds in mid-pregnancy; Considerable animal welfare and production benefits.
• Morris, S.T. etal., 2002. Mid-pregnancy shearing — a technique to improve lamb birthweight and survival. Final WoolPro Report.

Your local farm consultant or veterinarian can provide useful advice about mid-pregnancy shearing. Alternatively, contact your local WoolPro extension specialist: