Íslenskar landbúnaðarrannsóknir - 01.09.1981, Síða 54

52 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
partly be caused be depressed fertilizing
ability of ram semen in spring and
summer.
In connection with the out-of-season
breeding trials reported in this paper,
observations were made on ram libido and
mating behaviour. Each ram was intro-
duced to an oestrous ewe in an indoor pen
and observed for a few minutes. Table 2
shows that all the 21 rams tested in spring
and summer mounted the ewes presented
to them and 19 or 90% of them completed
matings with intromission and ejaculat-
ion. The results are considered quite acc-
eptable from a practical point of view.
One of the rams which failed to mate in
August 1979 was of very heavy body
weight (112 kg) and the other, a young
ram, had not been used for breeding in
December 1978.
Although these results were not based
on obje'ctive scoring of ram performance,
and included a small number of rams on
each occasion, they clearly indicated that
normal mating behavour was displayed
by most of the rams outside the normal
mating season.
Within each group of rams there was
marked individual variation in sexual
drive, as would be expected, and it was
interesting to note how certain individuals
known for great serving capacity in winter
appeared to perform similarly in spring
and summer. References to both indivi-
dual and breed differences in sexual act-
ivity of rams are well documented in the
scientific literature (Kilgour, 1980;
Land, 1970; Lees, 1978; Schanbacher
and Lunstra, 1976). Such differences
appear to be more pronounced outside the
normal mating season. Shackell, Kelly
and Allison (1977) found that rams in
New Zealand had the ability to mate at all
times of the year in spite of obvious seaso-
nal differendes in libido.
Although ram behaviour seems un-
likely to hamper the success of out-of-sea-
son breeding programmes in Iceland
some seasonal variation may exist in ram
performance and special attention should
be paid to semen characteristics. SCHAN-
bacher (1979) has demonstrated that ram
fertility may have a critical effect on the
lambing rate of ewes bred out-of-season.
In the present study there was limited
evídence of conception rates being affect-
ed by individual rams but due to the small
numbers of ewes allocated to each ram no
defmite conclusions can be drawn. Ne-
vertheless, it would seem feasible to select
certain rams for efficient breeding out-of-
season.
ACKNOWLEDGEMENTS
The author should like to thank Messrs. Sveinn
Runólfsson, Gunnarsholt and Sigurður Karl
Bjarnason, Hvanneyri, as well as their farm staíf,
for their kind cooperation.