How to Use EPDs to Select & Cull Sheep From Your Flock Using EPDs to select sheep or cull sheep in your flock is really a three-stage process: First, NSIP Fact Sheet you study your flock=s financial and management records to make the basic decisions about replacement rate and flock expansion. Then, you use the EPD reports from NSIP to guide NSIP- 007- NSIP-007-01 your preliminary selection of replacements and culls. Finally, you visually examine your sheep to make the final selections based on a combination of EPDs and visual appraisals. Step 1: Kitchen Table Analysis ♦ Before looking at individual animal records, look at the Big Picture of your flock C look at its current production level, its financial position, and your short-term and long-term goals. Carefully study your latest financial and management records. What are the production strengths and weaknesses of your flock? Compare these production records to the previous year C look for changes over time. Relate these changes to your goals and your selected traits. Which shortcomings can be improved through genetic From Within Your selection? Where should you put your efforts and resources? Flock ♦ Then decide how many ewes to cull and how many breeding animals to add. Are you Most sheep producers trying to increase your flock size or just maintain it? typically select replacement ewes from within their own flock. This practice is generally a good idea C it reduces health risks and Step 2: Using EPD Reports other Asurprises@ from ♦ Selecting from your own flock means that you are really making two different imported animals, it appraisals: (1) culling adult ewes that have poor records, and (2) selecting replacement eliminates transportation ewes and any additional animals for flock expansion from the best of this year=s lambs or stress and injuries, it yearlings. capitalizes on any unique adaptations by your sheep, ♦ Culling ewes B Generally, EPD reports from are sorted by sex, so that all the adult ewes and it allows you to evaluate are listed together (and the replacement lambs are listed separately). If you are using a your first-hand experiences spreadsheet or database program, sort the adult ewes on the EPDs of one trait that you with each animal. consider important, from highest to lowest EPD. (In computer jargon, the words Asort@ and Arank@ mean the same thing). Identify those animals at the bottom of the list. Consider culling ewes that are at the bottom rows of this ranking. ♦ Repeat this procedure for each trait of interest. Re-sort the ewes on each different trait and identify those ewes at the bottom of that list. For each trait, make a list of the ewes with the lowest EPDs. NSIP 6911 South Yosemite, Suite 200 ♦ Now go to your flock notes and study the production records for all your ewes. Examine Denver, CO 80112-1414 your notes for anything that indicates problem animals B ewes that didn=t raise all their Phone: (303) 771-5717 lambs, ewes that did not respond to footrot treatment, fence jumpers, genetic defects like Fax: (303) 771-8200 entropion, etc. Add these animals to your potential cull list. www.nsip.org NSIP Fact Sheet NSIP-007-01 Page 2 ♦ Selecting Replacement Lambs B Make your preliminary selection of replacements by examining the Aewe lamb@ and Aram lamb@ sections of your EPD results. Chose only the top lambs C these are ewe lambs and ram lambs with the highest EPDs in your trait(s) of interest. Choose a few more than your final replacement rate to allow for additional selection based on visual appraisal (see below). Note: Lamb EPDs may have lower Accuracy (ACC) values than adult ewes because lambs have less production information than adults. However, bear in mind that EPDs are still more dependable than any other selection method available today. ♦ Tied EPDs C If you must choose between two animals with the same EPD for a trait, Using Excel to Rank look carefully at the EPDs of their other traits and also use visual appraisal to break the tie. The Accuracy (ACC) value may also be useful in a tie. ACC is an indication of the Animals on EPDs reliability of an EPD C i.e. how much it may change as more data becomes available for If you use Excel or any that animal. Higher ACC values are better, but small differences are not biologically spreadsheet for your EPD significant. Choose the higher ACC value only if ACC values differ greatly (eg. 0.11 vs reports, learn how to use its 0.30). Sort command effectively. Sorting is a very powerful tool. Sorting will rank all the animals based on one or more trait of your choice, in Step 3: In the Pens C Do This Last: seconds, and you can repeat ♦ Now go out into the pens and visually inspect your animals. Put the ewes in one pen and the sort as often as you want. You must remember, the lambs in a different pen. This is where you apply your kitchen-table EPD decisions however, to select all the and also make culling decisions on obvious shortcomings, like poor legs or mouth or data when you sort in a other non-NSIP traits (e.g. does she jump fences?). EPDs are not designed to replace your spreadsheet, so that eyes or good husbandry, but EPDs can definitely improve the dependability of your everything on a row (in all selections. Note that the procedures for ewes and lambs are slightly different: the columns for that row) moves together. Otherwise, ♦ Ewes C Go through the entire flock and look at all your ewes. Place marks only on the the data across the columns following cull or questionable ewes: will become offset from the 1. First put two marks on any ewe that is no longer productive C ewes with non- animal identification, and functional udders, etc. C and also put two marks on any ewes at the very bottom you=ll have a real mess of your EPD lists. because the data will be scrambled and the EPDs 2. Then put one mark on any other ewe with problems C structural, health, or won=t line up with the correct behavior. These ewes are still functional, but are less than ideal. For example, animals. mark any ewes with a history of chronic bloat, vaginal prolapse, poor mothering ability, jumping, udder problems, not responding to footrot control, etc. Also mark any problem animals that you identified from your production records. These are all candidates for culling. 3. Then go through your ewes again and put one mark of a different color on those ewes with generally low EPDs. (You=ve already given two marks to the lowest EPD ewes in step #1. The ewes in step #3 may be better than the bottom, but they are still genetically inferior). 4. Now the final decision: cull any ewe with two or more marks. What about a ewe with only one mark? Here, you must choose between selecting on EPDs vs selecting on visual appraisal. Rule-of-Thumb: whenever possible, cull the ewes with low genetic value. Culling based on genetics has long-term effects in your flock, and NSIP Fact Sheet NSIP-007-01 Page 3 culling the low end of your flock will automatically improve your flock=s average. Draw a line at low EPDs. Cull all ewes below that line. Otherwise, ewes with low EPDs will pass their poor genetics to their progeny, which will haunt your flock for generations. ♦ Lambs C Place marks on lambs in a genetically superior subgroup and then from this subgroup identify lambs you don=t want to keep: 1. First mark those lambs with the best EPDs. Ignore the rest of the lambs C they don=t have superior genetics and should not be saved. 2. Then draft out these marked lambs and systematically go through only those animals, one by one. Put a second mark on any lamb that has an obvious problem C poor structural soundness, black fibers, overshot or undershot jaw, entropion, etc. 3. Don=t keep any lambs with two marks. Only keep the lambs with one mark C these are the sound lambs with superior genetics. Further For Further Information: SID Sheep Production Handbook, Breeding Chapter. The National Sheep Improvement Program acknowledges and expresses gratitude to the following persons for contributing to this document: Author: Woody Lane, Roseburg, Oregon. Reviewers: John Hough, American Polled Hereford Assoc.; Kreg Leymaster, ARS/Meat Animal Research Center; Lyle McNeal, Utah State University; Jack McRae, Jordan, MT; Dan Morrical, Iowa State University; Dave Notter, Virginia Polytechnic Institute; John Paugh, Bozeman, MT. Revised June, 2001.
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