Íslenskar landbúnaðarrannsóknir - 01.03.1979, Blaðsíða 86

84 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
draught horses but are included because
of close similarity with valuable charac-
ters of riding horses. The majority of the
estimates are obtained from half-sib anal-
yses, which, unfortunately, are in many
cases based on a rather limited amount of
data. Although hardly conclusive, the
majority of traits of concern are found to
have medium to high heritability. The
average heritability tor the traits measur-
ed in an objective way is 0.42, and 0.34 for
those evaluated by subjective scoring.
Body conformation
Several heritability estimates of body me-
asurements and evaluation of body con-
formation of horses are found in the liter-
ature (Dusek, 1965, 1970; Varo, 1965;
Watanabe and Siomiizaki, 1964; Kow-
nacki et al., 1969, 1971; Kalnaykow,
1975). The heritability estimates show fa-
irly good agreement and indicate that
body conformation and especially body
measurements are highly heritable. This
is in perfect agreement with investigations
of Gowen (1933), Touchberry (1951),
Weber (1957) and Skjervold (1958)
concerning body measurement of cattle.
Kownacki et al. (1971) found genetic,
environmental and phenotypic correlat-
ions between three body measurements,
taken on Wielkopolski Half-Breed horses
and English thoroughbred respectively,
all to be positive and fairly high.
Icelandic investigations
In a recent paper the heritability of tem-
perament in Icelandic riding ponies was
estimated to be 0.85 (Adalsteinsson,
1977).
The only estimates available ofgenetic
parameters of body conformation in the
population of Icelandic ponies are those of
10 body measurements (Árnason, 1975).
The data used, and which are to a minor
extent included in this study, were far too
limited in amount to obtain precise estim-
ates. The statistical analyses were made
separately for each sex. Apart from the
result obtained in the stallion group, the
estimates were in a rather close agreement
with those from other horse populations.
The consistently lower estimates obtained
in the stallion group could easily be a res-
ult of the great sampling variance, but
could possibly also indicate quite a high
selection pressure on the male side for size
(height, girth and foot measurements).
Estimates of phenotypic correlations
between the measured characters and ob-
viously very imprecise estimates of genetic
correlations were also calculated. Most of
the estimates obtained were positive and
many of the characters were seemingly
highly correlated, both phenotypically
and as a result of additive genetic covar-
iance.
MATERIALS AND METHODS
The material used in the present study
was obtained from the Agricultural Soc-
iety of Iceland. It includes records on
animals judged in connection with Icel-
andic horse shows between 1961 and
1976, with a total of 2074 individual
records. Some of the records were insuf-
ficiently filled in. This, together with the
fact that only those records containing in-
dentification number of sire (usually the
registered herd-book number) will be us-
ed in the statistical analysis, considerably
reduces the number of records actually
used.