Íslenskar landbúnaðarrannsóknir - 01.03.1977, Page 21

SOURCES OP VARIATION IN WEIGHTS OF LAMBS 19
For solving the equation following restic-
tions were imposed:
Ek. = Ea. = Er. = EEs.. = 0
i 1 j 3 k k ik lk
The analysis was done within sire groups
and within flocks. The effect of the age of <ú
lamb squared was not significant (P>0.05) J3
and was therefore excluded from the model. g
The effect of the interaction between type of &
birth and rearing and sex was significant m
(P<0.01) but the multipe correlation coef- m
ficient (R2) was reduced by only 0.00176 g
when it was excluded from the model. The
model used is an additive one, but the interac- §
tions is probably in part caused by the mul- kj
tiplicative effect of the sex and is therefore
not a real interaction effect. The final model ra
was therefore reduced by both effect of g
age squared and the interaction. |
Results from the analysis using this model ^
are shown in table 4. Effects of the different ■§)
factors in the model on weaning weight, g
measured by the reduction in R2 by ex- m
cluding the variables from the model are ‘Ej
shown in table 5. The far most important %
factor is the type of birth and rearing which
alone accounts for approximateiy 65% of ,u
the variation due to these variables. |
The age of dam takes account of only
1.7% of the variation, but in this analysis ^
there were only lambs from dams 2 years o
and older. When the age of the dam is ex-
cluded from the model a part of the effect >
of this factor will be measured by type of Jj
birth and rearing because of the confounding
of age of dam with type of birth and rearing.
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