In Practice 9: 167-170 (1987)
© 1987 British Veterinary Association

Infertility in the bull, ram and boar 3: Collection and examination of semen

The aim of these three articles has been to encourage a greater awareness in consideration of the male when investigating the reproductive performance of herd or flock. For many years there has been a tendency to concentrate more upon those aspects of management and disease which influence the fertility of the female, obviously both are important, but the male should not be forgotten! It is with this in mind that two concepts bear further mention, stud examination and the integration of AI and natural service.

Stud examination It is paradoxical that the sheep industry traditionally the most reactionary in accepting new ideas has been quick to realise the potential of a regular examination of males before their use. Undoubtedly this approach has been encouraged by the fact that in most flocks rams are run in mating groups and thus as detailed earlier subfertile individuals can be hidden. Initially such stud examinations involved the general examination and collection and examination of semen sample from each ram. However, in recent years there has been a growing trend towards only utilising this approach either in cases with a history of infertility or where the rams are run individually with groups of ewes. Thus in flocks with no history of fertility problems, the clinical examination of all the rams and their rejection either on the basis of this, or if felt necessary, backed by semen collection and examination is becoming more usual. The reasons for this approach have, it hoped, been made apparent earlier.

Integration of AI and natural service While not wishing ignore the genetic and disease advantages of Al it nevertheless appears that many progressive farmers are increasingly realising the advantages in using both. This is particularly so the pig industry. The three main reasons for Al use would appear to be, first to limit the risk of disease introduction, secondly to avail the herd of the continued genetic gain of nucleus pig breeders and breeding companies and thirdly ‘smooth-out’ fluctuations in service demands upon their boar stud. The outstanding reason for natural service is its simplicity in particular where there is any doubt as to the oestrous behaviour of the sow. A short period with the boar will soon confirm or deny it. Finally boar presence is an undoubted trigger to oestrus expression both in the sow and to its induction in the gilt. We believe that these principles will increasingly apply in cattle and even in sheep but that the exact relative proportions of services by Al, and natural service will vary depending on management strategies.

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Acknowledgements.— We gratefully acknowledge Dr H. Reed and Dr R. Ashdown for their advice and also Messrs A. O. Mathieson and C. L. Wright for their helpful comments.