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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
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. |
