Page 10 - Ranui Catalogue 2021 ebook
P. 10


                                 recessive genetic conditions
                This is information for bull buyers about the recessive genetic conditions, Arthrogryposis Multiplex (AM),
                   Hydrocephalus (NH), Contractural Arachnodactyly (CA) and Developmental Duplications (DD).
             Putting undesirable Genetic Recessive Conditions in   If  animals  tested  free  of  the  undesirable  gene  are
             perspective                         mated  to  carrier  animals  the  condition  will  not  be
                                                 expressed at all. All calves will appear normal, but
             All  animals,  including  humans,  carry  single  copies   approximately half (50%) could be expected to be
             (alleles) of undesirable or “broken” genes. In single   carriers.
             copy form, these undesirable alleles usually cause no
             harm to the individual.             How is the genetic status of animals reported?
             But  when  animals  carry  2  copies  of  certain   DNA-based  diagnostic  tests  have  been  developed
             undesirable  or  “broken”  alleles  it  often  results  in   which  can  be  used  to  determine  whether  an
             bad  consequences.  Advances  in  genomics  have   individual  animal  is  either  a  carrier  or  free  of  the
             facilitated  the  development  of  accurate  diagnostic   alleles resulting in AM, NH, CA or DD.
             tests to enable the identification and management   Angus Australia uses advanced software to calculate
             of numerous undesirable or “broken” genes.  the  probability  of  (untested)  animals  to  being
             Angus Australia is proactive in providing its members   carriers of AM, NH, CA or DD. The software uses the
             and their clients with relevant tools and information   test  results  of  any  relatives  in  the  calculations  and
             to  assist  them  in  the  management  of  known   the  probabilities  may  change  as  new  results  for
             undesirable genes and our members are leading the   additional animals become available.
             industry in their use of this technology.  The genetic status of animals is being reported using
             What are AM, NH, CA and DD?         five categories:
             AM, NH, CA and DD are all recessive conditions caused   AMF  Tested AM free
             by  “broken”  alleles  within  the  DNA  of  individual   Based on Pedigree AM free - Animal
             animals. When a calf inherits 2 copies of the AM or   AMFU  has not been tested
             NH alleles their development is so adversely affected
             that they will be still-born.        AM_%   _% probability the animal is an AM
             In other cases, such as CA and DD, calves carrying   carrier
             2 copies of the broken allele may reach full-term. In   AMC  Tested AM-Carrier
             such cases the animal may either appear relatively   AMA  AM-Affected
             normal, or show physical symptoms that affect their
             health and/or performance.          For NH, CA and DD, simply replace AM in the above
                                                 table with NH, CA or DD.
             How are the conditions inherited?   Registration  certificates  and  the  Angus  Australia
             Research  in  the  U.S.  and  Australia  indicates  that   web-database display these codes. This information
             AM,  NH,  CA  and  DD  are  simply  inherited  recessive   is displayed on the animal details page and can be
             conditions. This means that a single gene (or pair of   accessed by conducting an “Database Search” from
             alleles) controls the condition.    the Angus Australia website or looking up individual
             For  this  mode  of  inheritance  two  copies  of  the   animals listed in a sale catalogue.
             undesirable  allele  need  to  be  present  before  the   Implications for Commercial Producers
             condition  is  seen;  in  which  case  you  may  get  an
             abnormal calf. A more common example of a trait   Your  decision  on  the  importance  of  the  genetic
             with a simple recessive pattern of inheritance is black   condition status of replacement bulls should depend
             and red coat colour.                on the genetics of your cow herd (which bulls you
             Animals with only one copy of the undesirable allele   previously used) and whether some female progeny
             (and  one  copy  of  the  normal  form  of  the  allele)   will be retained or sold as breeders.
             appear normal and are known as “carriers”.  Most Angus breeders are proactive and transparent
                                                 in managing known genetic conditions, endeavouring
             What happens when carriers are mated to other   to  provide  the  best  information  available.  The
             animals?                            greatest  risk  to  the  commercial  sector  from
             Carriers, will on average, pass the undesirable allele   undesirable genetic recessive conditions comes from
                                                 unregistered bulls with unknown genetic background.
             to a random half (50 %) of their progeny.  The  genetic  condition  testing  that  Angus  Australia
             When a carrier bull and carrier cow is mated, there   seedstock producers are investing in provides buyers
             is a 25% chance that the resultant calf will inherit   of  registered  Angus  bulls  with  unmatched  quality
             two normal alleles, a 50% chance that the mating   assurance.
             will  result  in  a  carrier  (i.e.  with  just  1  copy  of  the   For further information contact Angus Australia’s
             undesirable allele, and a 25% chance that the calf   Breed Development & Extension Manager on
             will inherit two copies of the undesirable gene.
                                                 (02) 6773 4618.
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