Íslenskar landbúnaðarrannsóknir - 01.03.1977, Side 40

38 ÍSLENZKAR LANDBÚNABARRANNSÓKNIR
EFFECT OF THE AGE OF EWE ON EWE
BODY WEIGHT IN OCTOBER
AND JANUARY
In table 7 the analysis of variance for ewe
body weight is shown and in table 8 the
constants for the effect of age on body
weight are given. The age accounts for about
10% of the variation in the ewe body weight.
The maximum weight is reached at the age
of 5—6 years.
In Norway, Eikje (1971) found the hig-
hest ewe body weight at the same age as
found here but the age-effect was much
greater than found here. This might indicate
that the Icelandic sheep breed is an early
maturing one.
HERITABILITIES AND GENETIC AND
PHENOTYPIC CORRELATIONS
The estimates of heritabilities and genetic and
phenotypic correlations are shown in table 9.
The estimates for the number of lambs and
the score of lamb production are based on
26144 ewes sired by 3197 rams and for ewe
body weight on the records of 14079 ewes
sired by 2607 rams. Number of lambs and
ewe body weight are corrected by the con-
stants described before. An additive correc-
tion was used for the age effect.
The heritability of the number of lambs
born is found to be 0.19. Hallgrímssdn
(1966) found a heritability estimate of 0.13
by the use of half-sib correlation and 0.19
by the regression of daughter on dam. Adal-
steinsson (1971) found the heritability to
be 0.21 but he used only records of 2-year
old ewes.
Eikje (1975) estimated the heritability in
Norwegian data by half-sib correlation as
0.08 and 0.06 by regression of daughter on
dam. In Sweden Johannsson and Hansson
(1943) and Rendel (1956) estimated herita-
bility at 0.09—0.13. Purser (1965) esti-
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