Íslenskar landbúnaðarrannsóknir - 01.03.1979, Page 84

82 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
traits. The manifold and complex items
describing the conformation ofa horse are
weighted by the judges into three classes
asigned: form, proportions and legs.
The first trait, form, mainly reflects ex-
amination of the head, neck, shoulders
and the entire topline. An ideal type of
head is well proportioned to the rest of the
body, refined, cleancut, with chiseled ap-
perance; ears medium sized, well carried
and attractive. The neck should be fairly
long, thin, and cleancut from sloping sho-
ulders with the head well set on. The ideal
topline consist of clearly defined withers,
medium long back and loin, a long sloping
well muscled croup and a nicely set ta.il.
The scoring mark for proportions ref-
lects the balance, harmony and symmetry
in the development of all parts of the an-
imal. Ideal legs are squarely set, straight
and with pasterns of proper length and
slope; hoofs medium sized, dense and of
good quality.
The performance traits are scored ac-
cording to action in four gaits, as well as
temperament, character and elegance
under the rider. The first gait to be scored
is „toelt“ (rack), which is a special kind of
lateral gait, where just one foot touches
the ground at a time, with equal intervals,
thus offering a very smooth ride. The sec-
ond gait examined is trot where the an-
imal moves its feet diagonally. The third
gait is pace where the movements are late-
ral and finally the action at gallop is
judged. The Icelandic breeding horses are
not scored at the walk. The action of the
horses in all the gaits should be easy, smo-
oth and well balanced with straight, long
elastic steps; preferably rapid and fast,
especially at the pace and the gallop. The
temperament score reflects the spirit of the
horse and willingness to run. The charac-
ter score mark is given according to the
ease of handling of the horse; how it reacts
to the rider’s demands etc. The last trait to
be judged by the scoring index is elegance
under the rider which evaluates the ove-
rall picture of style, harmony and beauty
of conformation and movements of the
horse when ridden.
This scoring index is intended to be the
main basis for a selection amongst stall-
ions and potential dams ofstallions. How-
ever, no estimate exists of the selection
intensity nor the possibilities of impro-
vement by means of selection, i. e. estim-
ates of amount of additive genetic variat-
ion in the characters selected for.
The aim of this study js to estimate the
amount of some ,,tangible“ environmen-
tal factors and additive genetic variation
affecting these characters, using the point
scoring as a criterion. Results could poss-
ibly be a guide to more appropriate selec-
tion methods in the near future and offer a
prediction of expected responses to selec-
tion for the various characters.
Futhermore, additional records of four
body measurements are included in the
analysis of environmental factors and the
additive genetic variation.
REVIEW OF LITERATURE
Performance Traits
Previous investigations of performance
traits valuable for riding horses are not
numerous. Those concerned with genetic
studies have mainly been in the form of
heritability estimates. The bulk of this
work is reviewed in Table 1.
Some of the heritability estimates listed
in Table 1 are taken from populations of