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Beyond the Bale : March 2012
30 30 SELLING MORE WOOL September 2010 BEYOND THE BALE March 2012 BEYOND THE BALE 30 ON-FARM FAST FACTS l Management of ewe nutrition during pregnancy optimises lamb birth weight and survival l Ewes in condition score 3 at lambing are likely to wean more lambs. l There is considerable economic loss when ewes get pregnant but fail to rear a lamb. Managing ewes and pregnancy CONCEPTION RATE OF MERINO EWES AT DIFFERENT JOINING TIMES LAMB DATE JOINING DATE (DAY OF YEAR) PREGNANCY RATE (%) SINGLES (%) TWINS (%) May 1 Dec (330) 90 80 5 June 1 Jan (1) 110 90 10 July 1 Feb (32) 120 80 20 Aug 1 Mar (60) 130 70 30 Sep 1 April (90) 130 70 30 Oct 1 May (120) 120 80 20 When joining in the peak breeding season, at least 90% of Merino ewes get pregnant in the first two cycles. Pregnancy rates can be 10% lower if joined outside the normal breeding season. If more than 15% of ewes are not pregnant in the target mating time an investigation to determine the reason for ewes failing to conceive is necessary. Both ewe and ram problems can contribute to poor results. Consider pasture toxicities, including syndromes such as perennial rye grass toxicosis or oestrogenic clover infertility. Consult your animal health adviser to investigate problems. With joining for spring lambing getting into full swing, it is timely for woolgrowers to look at ways to maximise the reproductive rates of ewes and the survival of their lambs. The Wean More Lambs module of the Making More From Sheep manual provides woolgrowers with useful guidance (including procedures and tools) on the important management steps to improve flock reproduction rates and lamb survival to weaning. In this article we look at the some of the recommendations that the manual provides on managing ewes at joining and post joining. Extra profits can be achieved by improved management of ewes. The Lifetime Wool project has demonstrated that whilst stocking rate is the key driver, enterprise profits can be increased by $1 to $3 per ewe (an additional $1,000 to $3,000 per 1,000 breeding ewes) by managing ewes to appropriate condition score targets, even when stocking rate has been optimised. Part of the benefit comes from improving reproductive performance and part comes from increasing the lifetime productivity of progeny. MANAGING EWES AT JOINING The following management aspects need attention in breeding flocks: l Join maiden ewes and adults separately as they have different ram requirements. l Ewe health is extremely important. Any health issue such as worm burdens, liver fluke or footrot will slow weight gain or cause weight loss resulting in lower reproductive rates. l Avoid joining ewes within two weeks of shearing as shearing can disrupt cycling. l Avoid joining ewes in full wool. l Avoid joining ewes on pastures that may be toxic to sheep. For example, high endophyte perennial rye grass pastures may lower conception rates and lambing performance by as much as 20%, even without visible rye grass staggers. l Avoid severe stress (such as more than 1kg liveweight loss per week or extreme variation in feed quality) when joining ewes, as embryo loss may be higher. LENGTH OF JOINING Join rams with ewes for two 17 day cycles or five weeks. If your flock is mated outside the peak breeding season or joining paddocks are large, join ewes for six to seven weeks, or five weeks if teasers are used. Most ewes get pregnant in two cycles. On more intensively run farms, extending the joining for longer periods is not recommended because the 2-4% of extra lambs holds up completion of important management events such as marking and weaning. Delaying weaning for a few late lambs can result in serious worm burdens, leading to weight loss in both ewes and lambs. In winter lambing Merino flocks, the late lambs generally have poor survival rates because they have a lower bodyweight over summer. MANAGING EWES DURING PREGNANCY Managing ewe nutrition is the most important factor to ensure best reproductive performance. Condition scoring is a quick and reliable tool for managing ewes to meet production targets. The target condition score is a balance between reproductive performance, stocking rate and supplementary feeding costs. The most favourable nutritional strategy during pregnancy has the following key features: l Ewes can manage a fall from condition score 3 at joining to condition score 2.7 at day 90 of pregnancy where quality pasture is available to allow a gain in weight back to condition score 3 for late pregnancy. Otherwise, maintain condition throughout pregnancy. l Ewe condition score needs to be at least score 3 at lambing to minimise mortality and optimise wool and meat production of progeny. l When condition score cannot be increased by grazing management in late pregnancy, it is most profitable to maintain condition throughout pregnancy. If the ewes lose weight, supplementary feed. l The least cost option to meeting condition score targets is to match the breeding cycle with pasture availability. l In dry or drought years when the cost of supplementary feeding is very high, consider allowing ewes to fall to condition score 2.5 , but maintain satisfactory wellbeing levels.