Íslenskar landbúnaðarrannsóknir - 01.09.1981, Blaðsíða 60

58 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
a correlation analysis. Thus the following
significant correlations were established
between individual autumn values of test-
es diameter:
4 Oct. 1977— 5 Oct. 1978: r
5 Oct. 1978—28 Sept. 1979: r
4 Oct. 1977—28 Sept. 1979: r
The cyclical nature of the seasonal var-
iation in testes diameter of a group of 10
rams over a period of 24 months is illus-
trated in FIGURE 1 in relation to day-
length. The figure shows how the pattern
found during the first year was basically
repeated during the second year, i. e. the
highest values recorded in the autumn
followed by winter and summer values
with the smallest diameter in spring. The
DISCUSSION
For the purpose of the present study in situ
measurements of testes diameter could be
considered fairly accurate means of estim-
ating testes weight. Knight (1977) has
reported on the value of such estimates.
Testicular parameters are generally fo-
und to be highly correlated with body
weight and to a lesser extent with age of
ram lambs (Ólafur R. Dýrmundsson,
1973) and such relationships have also
been established in Icelandic ram lambs
(Ólafur R. Dýrmundsson, 1978b).
Flowever, in older rams which are close to
or have already grown to mature size,
correlations of this kind are likely to be
much poorer and even insignificant as was
the case here. Knight (1977) did not find
any significant relationships between the
age of adult Merino and Romney rams
and their testicular measurements. The
difference between the highest and the
lowest values was found to be 15% on the
average. The 10 rams, aged 1—4 years
when the measurements started, had me-
=0.6710; PC0.01; D.F.= 15
=0.7224; PC0.001; D.F.= 17
=0.7161; P<0.05; D.F.= 9
an body weights of 79.0, 86.8 and 91.0 kg
and mean testes diameters of 13.8, 13.4
and 13.4 in the autumns of 1977, 1978 and
1979, respectively, giving further support
to the finding that changes in age and
body weight did not account for changes
in testicular size. Moreover, an insignific-
ant correlation of r=0.1105 between testes
diameter and body weight was obtained
within years and seasons.
absence of any clear associations between
testes diameter and body weight in the
present study may partly be due to the fact
that the rams were maintained in good
condition throughout and only modest
changes in body weight occurred. The
lack of any relationship between the cycl-
ical variation in testis diameter and
changes in body weight is in a general
agreement with results obtained in Scot-
land (ISLAMand Land, 1977).
Although there was a clear indication of
seasonal variation in testes size in the
present study, more frequent measurem-
ents, e. g. at monthly intervals, would be
required to define more precisely the
cyclical pattern in relation to time of year.
Since testes diameter of adult rams app-
ears to be insensitive to modest changes in
body weight, and is unlikely to be inf-