The sperm picture of rams of different breeds as an indication of their fertility. II. The rate of sperm travel in the genital tract of the ewe

Abstract

Part I. 1. The sperm picture of rams of different breeds has been studied. 2. Semen was collected by Gunn’s electrical method. 3. The Ronderib Afrikaners were superior to the Merinos in semen characteristics . This may have been due to the fact that the former were younger rams. 4. There were too few rams of the other breeds represented to enable an opinion with regard to breed differences to be expressed. 5. A morphological study of spermatozoa was of great value and could be correlated with a ram’s fertility. It should, however, be considered together with the other semen characteristics. 6. When all the semen characteristics are considered together, a very accurate prognosis of a ram's breeding potentialities is possible. 7. The total number of abnormal spermatozoa in an ejaculum was not as good an indicator of spermatogenic activity as the type of abnormal cell. 8. Rams with poor fertility ejaculated more different types of abnormal spermatozoa than normal rams. 9. Variations in semen characteristics of different ejacula of the ram have been noted. 10. Semen of the less fertile rams showed greater variations than that of highly fertile rams. 11. Examination of two or three ejacula from an individual ram at weekly or fortnightly intervals is necessary in order to predict his breeding potentialities. A single examination may lead to erroneous conclusions. 12. The types of abnormal spermatozoa most consistently found in lesser or greater numbers in semen of all classes were tailless spermatozoa, coiled tails, and spermatozoa with defective stained anterior head caps. 13. Pyriform heads, narrow heads, enlarged middle pieces, filiform middle pieces, middle piece heads and variation in spermatozoon head sizes were relatively rare in good semen , but contributed appreciably towards a poor sperm picture. 14. Spermatozoa with coiled tails, in which the coiling involved mainly the ends of the tails, have been observed in semen in large numbers, without a corresponding reduction in fertilising capability of the semen. 15. High quality semen had good initial motility, good sperm concentration and few abnormal spermatozoa. 16. Poor quality semen may have a large volume and a high sperm concentration. 17. Seven of sixteen rams gave higher numbers of abnormal spermatozoa in summer than during any other season; in the remainder the abnormality counts were highest in winter. 18. Sperm concentration and total numbers were highest in winter and lowest in late summer. 19. Semen volume could not be definitely correlated with seasonal changes. 20. Initial motility was not affected by seasonal changes. 21. In general rams with had sperm pictures and poor fertility were more readily affected by climatic conditions than normal rams. Part II. 1. Spermatozoon vitality is rapidly reduced in the vagina of the ewe. A few spermatozoa still showed weak motility in the vagina 20 hours after copulation. 2. The cervical canal is the most favourable site for sperm preservation. 40 per cent. of spermatozoa in the cervix were motile 20 hours after copulation. 3. Spermatozoa progress from the cervical canal continuously and in small numbers. 4. Spermatozoa were found in the uppermost section of both fallopian tubes 6 minutes after ejaculation. They had travelled a distance of 45 cm. at the rate of 7.5 cm. per minute. 5. The progress of spermatozoa along the genital tract was independent of ovarian activity and the time ewes were in oestrus. 6. Degenerative changes in spermatozoa were observed in the vagina of the ewe 2 hours after copulation, and in the cervical canal after 5 hours.