Íslenskar landbúnaðarrannsóknir - 01.09.1981, Page 60

Íslenskar landbúnaðarrannsóknir - 01.09.1981, Page 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-

x

Íslenskar landbúnaðarrannsóknir

Direct Links

If you want to link to this newspaper/magazine, please use these links:

Link to this newspaper/magazine: Íslenskar landbúnaðarrannsóknir
https://timarit.is/publication/1499

Link to this issue:

Link to this page:

Link to this article:

Please do not link directly to images or PDFs on Timarit.is as such URLs may change without warning. Please use the URLs provided above for linking to the website.