How to Use EPDs to Select Cull Sheep From Your Flock Cull Sheep by thebest11


									                                  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
  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.
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.
                                                                                                                  NSIP Fact Sheet
       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
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.

         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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