Íslenskar landbúnaðarrannsóknir - 01.03.1977, Síða 36

34 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
Table 3. Analysis of .variance. Number of lambs at weaning.
Ewes with recorded
All ewes body weight
Source of variation ■D.F. M.S. D.F. M.S.
Total, within flock 37463 0,223 18469 0,224
Total reduction 7 29,026 13 15,166
Age of the ewe 7 29^026^ 7 ö^os?^
Regression, date of rnating 1 8,121“
Regression, date of mating squared 1 7,618“
Regression, body weight in Oct. 1 0,033
Regression, body weight in Oct. squared 1 0,055
Regression, 'body weight in Jan. 1
Regression., body weight in Jan., squared 1 9,544XX
Residual 37456 0,217 18456 0,214
R2 0,0243 0,0476
RESULTS
Systematic factors affecting
the number of lambs.
The results of the least squates analysis of
variance for the number of lambs born and
number of lambs weaned are shown in table
2 and 3. There is found to be a significant
effect (P<0.01) of ail factors in the model
used on a number of lambs except of ewe
body weight in October. The body weight
of ewe in October is highly correlated (r=
0,85) with ewe body weight in January
and when January weight was excluded from
the model the effect of ewe body weight in
October became significant (P<0.01).
The age effect measured by the multiple
correlation coefficient is only 2.7 % for num-
ber of lambs born and 2.4% for number of
lambs weaned. Hallgrímsson (1966) who
studied the effect of various factors on number
of lambs at birth in two breeding associations
for the years 1940—1961 found that the age
effect accounted for 3-9% of the variation
in number of lambs born. The reason for a
lower age effect in the present study may
be that the material is from the whole country.
Selection may also have been carried out
for earliermaturing ewes and the rearing may
have been better.
The constants for the age effect are shown
in table 4. The highest number of lambs
born is produced by the five year old ewes,