Íslenskar landbúnaðarrannsóknir - 01.03.1977, Blaðsíða 85

ÍSL. LANDBÚN.
J. AGR. RES. ICEL. 1977 9,1: 83-88
The effect of ram on ewe fecundity
in Icelandic sheep
SVEINN HALLGRÍMSSON
The Agricultural Society of Iceland.
ABSTRACT
Some farmers in Iceland claim that the ram affects the ewes fecundity. Investigations or experimental
results supporting this opinion have so far not been available. This investigation was therefore planned
to obtain some information on this phenomenon. Data from the sheep recording associations in Ice-
land was used and the analyses were done in three ways. a) On the whole material b) excluding
barren ewes and c) grouping the matings according to the relationship between the ram and the ewe.
No differences were found between rams with respect to fertility, measured as the ram effect on the
ewes fecundity, irrespective of whether fecundity was measured as number of lambs born per parturi-
tion or fertility of mated ewes. However, when the matings were grouped into two classes ie., none or
little blood relationship between ram and ewe on one hand and 12.5% relationship or more on the
other hand, a significant difference was found between groups, the ewes in the group with the closer
relationship giving fewer lambs born per ewe mated.
INTRODUCTION
Some farmers in Iceland have been of the
opinion that the rams affect the number of
lambs born by the ewes they serve. There
are, however, very few investigations on this
subject in the Icelandic sheep and under the
Icelandic management conditions, although
it is known that in special cases marked ram
effects have been found (Adalsteinsson
and Hallgrímsson, 1977). In one investiga-
tion a significant effect of the colour geno-
type of the ram on ewe fertility has been
found in the Icelandic sheep (Adalsteins-
SON, 1970), and in another case increased em-
bryonic mortality caused by the ram has been
found to occour (Adalsteinsson and Hall-
grímsson, 1977).
In Icéland it is almost an overall practice
to hand mate the ewes (Adalsteinsson,
1970), and on many farms each ewe is mated
twice during the heat, with 8—24 hour
intervals. The Icelandic farmer usually has
some 300—400 breeding ewes, and he will
in most cases have decided before the start
of breeding season which ram the different
ewes are to be mated with. This mating
practice and eventually a high inherent fe-
cundity may be determining factors for the
low percentage of barren ewes in the Ice-
landic sheep, as it is commonly about 2.0%
in the recorded flocks with 50—60000 an-
nual records.
The aim of this study was to investigate