Daily spermatozoan output from the urogenital tract (DSOU), scrotal circumference, testis weight, and the numbers of spermatozoa in the epididymis and other parts of the urogenital tract were measured in 10 rams. Testis weight and the numbers of spermatozoa in the head, body, and tail of the epididymis and in the vas deferens and ampulla were found to be bilaterally symmetrical in each ram. The daily spermatozoan output from the urogenital tract was linearly correlated with testis weight (r = o· 83), with epididymal spermatozoan reserves (r = 0'86), with extragonadal spermatozoan reserves (r = 0·90), and with the total number of spermatozoa in the urogenital tract (r = O· 84). The significance levels of the regression coefficients indicated that these parameters would give good estimates of each other. The total number of spermatozoa in the urogenital tract of all rams at slaughter divided by the predicted time taken for spermatozoa to traverse the tract was found to be approximately 6% below the mean value for the daily spermatozoan output of all rams.

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The extent of prenatal losses of ova was studied in one hundred 5�-year-old Peppin Merino ewes mated with two rams for five weeks in November-December. Of a potential of 157 ova, the minimum losses due to ewes mating but losing all ova, and to ewes losing one ovum out of two or three shed, were 9.5 and 12.7%, respectively.There was a significant effect of pre-joining liveweight on ovulation rate, and evidence of a difference between sires in the proportion of ova lost by ewes with multiple ovulations.