Íslenskar landbúnaðarrannsóknir - 01.03.1977, Síða 86

84 ÍSLENSKAR LANDBÚNAÐARRANNSÓKNIR
whether the ram affects the number of lambs
born, and/or the number of barren ewes,
and to see if the blood relationship between
the ram and the ewe it serves affects the
same trait.
MATERIAL AND METHODS
Data from the two recording associations
was in this investigation the associations are
"Thistill” in North-East and "Myrahrepps”
in South-East Iceland. Both these associations
have been active for a long time, the former
being formed in 1940 and the latter in 1941.
The material used here covers the period
1945 to 1961, both years included. There
were 4 flocks in the Thistill sheep recording
association, through all years, and 9 flocks
the first year and 13 flocks the íast year in
Myrahrepps sheep recording association.
Orignally there were 12.651 observations
having the necessary information. Devided
according to classes of fertility the following
distribution was observed:
Fertility of the ewe...... 0 1
Number of observations .... 308 6337
This gives an overall mean of 1.45 ±0.004
lambs per mated ewe (alive at lambing).
As the ewes having triplets are very few,
only 0.27%, it was decided to delete them
from the analyses. It has been pointed out that
fertility of ewes defined as a number of
lambs born per parmrition and the ability
of the ewe to have lamb or fail to have lamb
(be barren), might be two different characters
Class of relationship ......
Number of observations ....
(Young, et. al. 1963, Purser, 1965). There-
fore, it was decided to carry out the analyses
on the material bot with and without barren
ewes.
The data used here are, as mentioned
above, taken from the sheep recording in
Iceland. This activity is organi^ed by the
Agricultural Society of Iceland and obtains
financial support from the Goverment. The
data is recorded by the farmer himself. The
data is then brought to the Agriculmral
Society, which takes care of the processing.
One of the information items recorded is the
relationship between the ram and the ewe it
serves. This relationship was recorded as a
coded abbreviation and there is not taken
into account the effect of inbreeding on the
relationship. According to the degree of rela-
tionship the matings were grouped into
following four groups:
1. None or little relationship (<0.125)
2. Relationship 0.125
3. Relationship 0.250
4. Relationship 0.500
As there is only the relation between the
ram and the ewe taken into account and
not the inbreeding of these, the actual rela-
2 3
5972 34
47.21 0.27
tionship between the ram and the ewe will
never be less than indicated above. Some
of the records did not have information on
the relationship between the ewe and the
ram and were therefore excluded from the
material in these analyses. The total number
of records used in this analysis was 11.108,
distributed on group of relationship as shown
below.
1 2 3 4 Total
10.133 409 375 209 11.108
Analyses of variance and regression ana-
lyses vere carried out within flocks and year