Thursday, July 7, 2022

Winter management of grazing ewes

Planning now will underpin lambing results for spring 2013, writes Brendan Brier. The management of ewes over the winter from the date that the ram goes out until the start of lambing is a challenging time on any sheep farm. Last season saw a high degree of wastage on many farms with high ewe deaths (8-9%) and low lamb survival (around 70% survival from scanning to docking). The summary below sets some guidelines that can help in setting your winter feeding plan. The aim of the winter plan is to move the lamb survival to better than 82% of the potential lambs scanned and reduce ewe deaths to less than 6%. The obvious place to start is a winter feed budget but this article focuses on using pasture residuals to control intakes.

The first point is that the lightest ewes in the flock need to be separated and preferentially grazed. This decision should be made on body condition score (BSC) to ensure that these sheep at least maintain, if not improve, their condition.

Feeding over the first 50 days from when the ram joins the ewes is critical to setting up the placenta. This ensures that the cotyledons are well implanted and sets up the foetus for best nutrition over gestation. This means that the ewes should be fed ad-lib during the first 20 days after joining (residuals of 1200kg DM/ha or 2.5cm pasture height). The residuals can then be reduced to 800kg DM/ha or 1cm over the following 30 days.

From day 50 to day 100 after joining, the second trimester is an opportunity to maintain ewe weight. The target should still be to deliver the ewes at a condition score of 3 at the end of the 100 days. This means that the residuals can be reduced to 600kg DM/ha or less than 1cm.

This mid-pregnancy period is still considered the best time to shear ewes to stimulate heavier lamb birth weights by 5%. This is intended to improve the lamb survival at lambing time.

From day 100 to set-stocking, 10 days pre-lamb, the intake is increased with residuals lifted to 800kg DM/ha or 1-2cm. At day 115 (five weeks pre-lamb) the twins and triplets are separated from the singles and preferentially fed to minimise underlying body weight loss. Ideally, multiple ewes should be a BSC condition score of greater than 3 at set-stocking to improve lamb survival.

The set-stocking of multiple ewes 10 days before the planned start of lambing will enable the ewes to find a lambing site before they start lambing. Single ewes can be held up and set-stocked at three days before the planned start of lambing.

The use of harnesses at 10-day intervals during mating allows for greater control of feed demand at set-stocking with the ability to delay the set-stocking of the ewes with later conception dates. This provides greater flexibility when pasture covers may be tight. The harness regime should be no harnesses from day 0 to 10, blue harness from day 10 to 20, and red harness from day 20 to ram out.

The target is to have an average pasture cover of 1350-1400kg DM/ha at lambing (3-4 cm). The multiple ewes will be set-stocked on longer paddocks with a record of better lamb survival based on historical docking percentages.

This sounds straightforward but a typical farm needs a few design considerations. The ewes need to be shifted every three to four days and maintain a rotation speed of 60-80 days. This means that a typical flock needs at least 20 paddocks for the winter rotation before splitting the flock.

Triplet and quad-bearing ewes are still an area of frustration with typical docking percentages being 180% to 220% from a paddock set-stocked with triplets. Intensive management doesn’t appear to provide a reasonable cost benefit and intervention proves to have only a marginal advantage. Best results have been achieved using speciality crops (e.g. chicory/plantain).

A key area of wastage last season was cast triplet ewes resulting in the loss of a potential income of $275/ewe. Regular monitoring in the lead-up to lambing is needed to ensure any cast ewes are recovered as quickly as possible.

Animal health needs to be well-planned. All the vaccinations should be up-to-date (toxo and campy), administer a 5-in-1 vaccine within three weeks pre-lamb, and make an informed decision if a pre-lamb drench is given and about what drench type to use. This advice is specific to each farm and best provided by a skilled local vet.

By managing the ewes carefully throughout winter, lamb survival can be improved significantly as well as ewe wastage reduced. Planning now will underpin results for spring 2013. 

Brier Ag Consultancy – 0800 4 BRIER

brendan.brier@xtra.co.nz

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