Breed Standards - Sussex Cattle Breeders Society

selection, although management skill is
a prerequisite and a good farming
contributory factor. With efficient
selection we mean the ability accurately
to judge the value of an animal as well
as good judgement on the relative
importance of the various traits for
which are selected. In practice,
selection progress will be determined
by the following factors (over which we
have no control):
• The number of traits for which are
selected, limit this to a minimum.
One wonders often, for example,
whether it is worthwhile to divide a
trait such as conformation into head
and neck, forequarters, middle piece
and hindquarters. In practice, the
points awarded are so often
determined by the size of the animal
that it would perhaps be better only to
point a “general appearance”. Size
and body size can rather be
described in terms of objective
measuring.
• The proportion selected. This
determines the superiority of the
selected animals and is therefore
extremely important. In practice it
will depend on reproduction rate and
replacement needs. The latter, in
turn is largely determined by the
generation interval, which we will
discuss later.
• The accurate elevation of animals.
This is one of the most important
aspects of selection. The accuracy of
selection, firstly, directly determines
the response obtained by selection.
Secondly , the figures so obtained are
priceless value to determine breeding
policy. Many futile arguments take
place about breeding policy simply
because the data on which
arguments can be based, are not
19
available. Measuring the
bookkeeping is imperative if one
strives for maximum breeding
progress. Without it, it is not even
possible to determine the extent and
nature of the progress that is being
made.
Population Size
After the objective has been set and
decisions on accurate measuring
techniques have been taken, the
selection progress will further depend
on the effective size of the breeding
unit. Population size influences the
selection progress in a dual way: the
possibility of achieving favourable gene
combinations are better in a large
population, and risk of in-breeding
smaller. The gene pool of any member
of individuals found in such a species
represents but a fraction of the
potentially possible gene combinations.
The larger the population is, therefore
the better are the chances of getting
individuals with favourable gene
combinations. It has, in fact, been
found in selection experiments with
vinegar flies, that a low selection
pressure in a large population brings
about more progress than a high
selection pressure in a small
population. It is also noteworthy that
the top studs in any ramification of
animal breeding are always of an
above average size. It is sometimes
said that apart from the
knowledgeableness a stud breeder also
needs a bit of “luck” to get to the top. In
my view this luck element is strongly
connected with stud size. Provided
other factors are even, the large stud
will be “luckier” than the small one.