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Selection based upon testicular diameter adjusted for body weight at 6, 10 and 14 weeks of age was used to produce two lines of sheep, with either high or low testicular size. Ten generations of selection were carried out and the estimate of the realized heritability of the selection criterion was 0.53 +/- 0.01. There were significant positive correlated(More)
Plasma LH levels were examined at 1 1/2-hr intervals in ram lambs of the Finnish Landrace, Border Leicester and Cheviot breeds on three occasions at 3-week intervals by radioimmunoassay. On each occasion, the mean plasma LH concentration was found to be significantly higher in the Finnish Landrace than the other two breeds, although big variations occurred(More)
Season but not hemicastration affected the cellular composition of the testis. Despite similar weight, the testicular histology differed markedly with season of birth. The number of Leydig cells and of Sertoli cells was greater in summer- than in winter-born lambs by factors of 2 and 1.5 respectively. Similarly the number of spermatogonia and their rate of(More)
The concentration of oestradiol was measured by radioimmunoassay in ovarian venous plasma collected from ewes of three breeds (Finnish Landrace, Scottish Blackface and Tasmanian Merino) on Day 9 of the oestrous cycle and in jugular venous plasma collected daily around oestrus in two of these breeds. The mean +/- s.e.m. concentration in the ovarian venous(More)