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Explanation of decisions taken on top crossing or upgrading Nguni Cattle to SP status

Dr Michiel Scholtz from the ARC was requested to investigate the issue of upgrading Nguni cattle and to report back at the November 2005 Council Meeting and Annual General Meeting.

He reported on two techniques namely top crossing and upgrading, which are very similar.  A top cross is made when a breeder goes  back to the original genetic source of the breed for some new genetic material. In the case of the Nguni this will imply to go back to the traditional custodians of the Nguni to collect such new genetic material (bos koeie en bulle).

 

Upgrading is where one breed is changed (graded up) to another by continued crossing.  It has been widely used throughout the world where stock was graded up by a number of crosses from registered sires (SP) from a specific breed.  It is commonly accepted that four generations of crossing with a registered sire (SP) will result in purebred status.

 

A upgrading programme will work as follows:

 

Unspecified original Female x Registered Sire (SP)

(50% pure) Female x Registered Sire (SP)      (F1)

(75% pure) Female x Registered Sire (SP)      (F2)

(87.5% pure) Female x Registered Sire (SP)    (F3)

(93.75% pure) Female (SP)

 

A third scenario is that of a closed herd book where only SP  x  SP matings can result in SP progeny.  An example of such a breed is the Black Angus with 15 million animals in the Herd Book.  In spite of the closed system the breed is still the biggest cattle registry in the world.

 

The latter system is not an option for the Nguni.  However, the current situation in the case of the Nguni is a mixture between top crossing and upgrading.  Due to this unique situation the Nguni should have a unique approach based on sound scientific principles.

 

In the case of the Nguni the original genetic source does not have a breed registry.  Therefore breed purity can not be guaranteed, albeit this source still has large numbers of animals with unique Nguni characteristics.  This dilemma necessitates a process of upgrading of animals from this source or from any other source where the animals appear to be phenotypically Nguni.  Recognizing the value of such genetic material, but also the possible infusion of “foreign” genetic material that is not phenotypically visible, the Annual General Meeting approved  the following process:

 

First Registration (FR) x FR, A, B or SP App A
(phenotypic Nguni)
App A
x A, B or SP App B
App B
x B or SP SP

 

First Registration refers to phenotypically Nguni animals that enter the Nguni register from the first time, e.g. a farmer that has been farming commercially with Ngunis and now wants to become a Stud Breeder.  It does not refer to animals that were downgraded or reinstated (for which the original bylaws still apply).  This system also specifically caters for emerging black farmers that want to become Nguni Stud breeders, and they are encouraged to enter the Seed Stock Industry.

The Advantages of this System are :

1.  More opportunity to replace unknown genetics with Nguni genetics by adding an additional upgrading generation
2.  One extra generation for unwanted genes to segregate so that they can be identified and eliminated.  A simplistic example is given
     below :

Example :

Genetic composition of First Registration Animals is NP which appears to be phenotypically Nguni.  However, N represents Nguni genes and P unwanted genes
 

i)  First Registration:  NP genetic composition

ii)  Intermate NP x NP
 

 
  N P
N NN NP
P NP PP
 


  NN      :      NP      :      PP     
      App A
(25%)       (50%)        (25%)
Cull all PP due to unwanted genes
 

iii)  Intermate NN and NP
 

  NN      :      NP      :      PP            App B
(44%)      (37.5%)    (12.5%)
Cull all PP due to unwanted genes

 

iv)  Intermate NN and NP
 

  NN           :      NP       :      PP            SP
(56.25%)      (37.5%)    (6.25%)
 

 

Note:  Upgrading is not feasible at this stage since it imply that only SP bulls can be used in the process through a F1  to F4 system

 

Restriction on sale of First Registration

 

It is important at to ensure that First Registration (FR) animals not only look like pure Ngunis, but they must also breed and perform like pure Ngunis and meet the minimum breed standards. 

 

At the November 2005 Meetings, a moratorium of four years was put on the transfer of first registration animals.  However, this restriction does not necessarily ensure that such animals breed and perform like pure Ngunis.  At the Council Meeting of 30 and 31 May 2006 the limitation on the transfer of first registration animals was thus re-formulated.  FR Animals must now comply with the following requirements before they can be transferred:

 

Females

1.  The cow must have at least one calving interval and her average calving interval must not exceed 550- days
2.  At least one of the cow’s calves must have passed an inspection

 

Bulls

The bulls must have at least 20 progeny submitted for inspection of which 50% passed the inspection

 

Note:  It is a Club’s prerogative to decide whether first registration animals can be sold under the auspices of the Society or not.

   
 
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