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Beyond the Bale : December 2010
December 2010 BEYOND THE BALE 26 ON-FARM Flock owners are rediscovering with zeal that there's one easy and effective tool to optimise ewe flock performance -- pregnancy scanning. With sheep prices so high, the push to rebuild numbers and use surplus available feed (in eastern Australia), both Merino and crossbred producers are calling on scanners to help lift conception rates, lamb survival and weaning percentages. Industry & Investment NSW Livestock Officer (Sheep and Wool) Chris Shands is working with the Sheep CRC to promote the value of scanning, and take it several steps further. "Traditionally, the preg scanners were just asked to identify the 'wets' and 'drys'. Then, those which are not in-lamb are re-joined, run dry as woolcutters or sold," Chris says. "But, we can use the scanning information to do more by identifying drys, singles and multiples. This means the multiple-bearing ewes can be separated, and preferentially fed and managed, to optimise lamb numbers and survival. "In tandem with good record keeping, regular scanning can and is now being used to increase the overall flock average reproductive rate year-on-year." Chris says much of the detail supporting the use of scanning comes from the industry's investment in the lifetimewool program, which found there is substantial scope to improve reproductive performance in most flocks because of the variability that exists - see Table 1. He suggests producers use scanning records and a simple calculator to assess flock conception, lambing and marking rates. Table 2 is based on a ewe mob of 350 head. Chris says that the final figure of 71%, while fairly typical, indicates that there are significant gains that can be made in ensuring high conception rates translate to high marking rates. Lifetimewool also identified the optimum birth weight range of twin and single born lambs as between 3.5kg and 5.5kg. Lambs with birth weights at 6.0kg or heavier have greater chance of dystocia (difficult birth). To try to avoid single bearing ewes experiencing lambing difficulties, and ensure optimal survival, Chris suggests that producers adjust stocking rates of single and multiple bearing ewe groups in the last month of pregnancy: lPasture targets for single bearing ewes should be no more than 800kg of green feed (no more than 2cm of pasture height). A useful technique is for singles to follow cattle or twin bearing ewe groups that have grazed pastures down. lTwin bearing ewes need a minimum of 1200kg of green dry matter per hectare (3cm to 4cm pasture height). If this pasture target cannot be achieved then a balanced supplement of energy and protein needs to be fed. As part of the effort to underpin the use of scanning technology, the Sheep CRC assisted with the set-up and conduct of the inaugural sheep scanning conference earlier this year, in Victoria. Scanners attended from around NSW, South Australia, Victoria and Tasmania, and temporarily setting aside their tools-of- trade, a tube of gel and an ultrasound unit, they canvassed tools and techniques to ensure accuracy and efficiency. Chris says conference outcomes also included that: l scanners are looking forward to developing improved scanning hardware and the potential to interface electronic ear tags with data capture, collection and management to further improve animal husbandry and farm efficiency; and l scanners are keen to contribute to a data collection and management program which could show trends in scanning results on a local, regional and national basis. More information: For more information on scanning or ewe and weaner management workshops, contact Chris Shands, 0411 139 702 or see the Sheep CRC website: www.sheepcrc.org.au/education/ industry-training.php FAST FACTS l Pregnancy scanning can be an effective tool to optimise ewe flock performance. l Multiple-bearing ewes can be separated, and preferentially fed and managed. l The work builds on past investment in the lifetimewool program. The resurgence of scanning TABLE 2: LAMB CONCEPTION TO MARKING CALCULATOR Number of ewes joined A 350 Number of lambs scanned B 465 Scanning percentage (B/A x 100/1) 133% Number of lambs marked C 332 Marking percentage (C/A x 100/1) 95% Lambs marked to scanned percentage (C/B x 100/1) 71% TABLE 1: EWES RANKED ON LIFETIME REPRODUCTIVE PERFORMANCE REPRODUCTIVE COMPONENT LOWEST 25% LOW-MEAN 25% MEAN-HIGH 25% HIGHEST 25% EWE FERTILITY 55% 78% 88% 95% LITTER SIZE 1.28 1.42 1.42 1.64 LAMB SURVIVAL 47% 83% 83% 90% LAMBS WEANED/ EWE JOINED 0.30 1.00 1.00 1.39 LAMB BIRTH WEIGHT DRIVES SURVIVAL Single lambs (av. birth wt 4.9kg) Twin lambs (av. birth wt 3.7kg) LAMB SURVIVAL (%) BIRTH WEIGHT (kg) 01 2 4 6 8 20 40 60 80 100